Fig.1. Hand coloured copper engraving of Iceland and some of its volcanoes, from the Physical Atlas by Heinrich Berghaus (1838-48) (image in public domain).

Volcanoes are nothing unusual on Iceland, but the eruption that started June 8, 1783 was one of the deadliest events we remember.
In six months estimated 14 cubic kilometer of lava poured out from a total of 135 fissures near the old crater of Lakagigar (Lakagigar is a single mountain, Laki ist the name given to the chain of craters of the 1783 eruption), covering estimated 2.500 square kilometer of land.
One of the eyewitnesses – the shepherd Jón Steingrímsson – described horryfied the unfolding disaster:

“First the ground swelled up with tremendous howling, then suddenly a cry shattered it into pieces and exposing  {the earth´s] guts, like an animal tearing apart its prey.
From the smallest holes flames and fire erupted. Great blocks of rocks and pieces of grass were thrown high into the air and in indescribable heights, from time to time strong thunders, flashes’, fountains of sand , lightening [?] and dense smoke occurred… Earth trembled incessantly. …how terrible it was to see, such signs of an angry god…[now] it was time to confess to the lord.“

More than 9.000 people were killed by the direct effects of the eruption, like lava and poisonous gases. The ash was carried away with the wind and poisoned the land and the sea, killing half of the Icelandic cattle population and a quarter of the sheep and horses population. Nothing would grow on the fields and no more fish could be found in the sea. In the resulting famine (1783-1784) estimated twenty thousand people – one-third of the population of Iceland – died.

But the Laki eruption had possibly even more widespread effects. In the years after the eruption the climate in Europe deteriorated, characterized by cool and rainy summers. The resulting crop failures triggered one of the most famous insurrections of starving people in history – the French Revolution of 1789-1799.

Bibliography:

BOER, de J.Z. & SANDERS, D.T. (2004): Das Jahr ohne Sommer. Die großen Vulkanausbrüche der Menschheitsgeschichte und ihre Folgen. Magnus-Verlag, Essen: 269
DAVIS, L. (2008): Natural Disasters. Facts on File Sience Library. Infobase Publishing: 464

The expedition’s most ambitious goal was to establish a base 400km farther inland, in the center of the ice cap itself, named appropriately “Mid-Ice“. In late autumn the station Mid-Ice was ready, manned by Georgi and Sorge, however both men were unsure if the supplies would last for the entire winter. September 22, Wegener and Loewe organized an expedition to bring the necessary supplies to Mid-Ice, temperatures were dropping fast and the first winter storms approaching -  soon only one young Inuit – Rasmus Villumsen – was willing to continue with Wegener and Loewe. The three men were ably only to transport a limited amount of material and so left back the radio – as they arrived to Mid-Ice on October 30, they knew that the supplies would never be sufficient for five persons. Only Loewe remained, as he had suffered a severe frostbite on his toes, which had to be amputated by Georgi with a pocket knife, he was not able to walk.

November 1, 1930 the men celebrated Wegener’s 50th birthday with some dried fruit and chocolate (a rare luxury during Arctic expeditions) and after some hours Wegener and Villumsen left for their long journey back to the safe coast. Whit no radio aviable, Georgi, Sorge and Loewe couldn’t inform the Western Camp of Wegener’s and Villumsen´s departure and had to wait until the Arctic spring for news.

Fig.1. Last photograph of Wegener and Villumsen taken on November 1, 1930, before they set out from Mid-Ice on their unsuccessful attempt to reach Western Camp, published in GEORGI (1935) “The Story of the Wegener Expedition to Greenland” (image in public domain).

April 23, 1931 another expedition was send to Mid-Ice, about halfway they found a pair of skis and ski pole in the snow, but continued until Mid-Ice, where they meet Sorge, who asked “Where´s Wegener?” Sorge and a part of the rescue team returned to the site , digging below the skis they found Wegener on May 12, 1931, carefully wrapped in two sleeping bag covers and laid on a sleeping bag and a reindeer skin. Karl  Weiken, one member of the rescue team, wrote that Wegener’s face appeared “relaxed, peaceful, almost smiling” and “looked more youthful than it had before.” Villumsen had buried Wegener with great care, taken his diary and some personal effects with him, maybe hoping to make it until the Western Camp. Villumsen was never found.

The German government wanted to bring the body back to Germany for a state funeral, but Else Wegener, Wegener´s wife, knowing of Alfred´s love for the Arctic, refused and so Wegener was left where Villumsen buried him.

Today his grave is long vanished beneath the ice, slowly drifting west – not only carried by the flow of the ice towards the sea, but also by the westward movement of the North American Plate.

A tribute to Alfred Wegener by “The Amoeba People”

Bibliography:

FRANKEL, H.R. (2012): The Continental Drift Controversy, Volume I: Wegener and the Early Debate. Cambridge University Press: 604
YOUNT, L. (2009): Alfred Wegener -Creator of the Continental Drift Theory. Makers of Modern Science Series, Chelsea House Publishers, New York: 160

There is lot fuzz about the discovery of a slab of granite embedded into basaltic rocks of the oceanic crust – granite is a rock typical of continental crust (including island arcs), which prompted journalists to claim the discovery of a sunken continent (and no, dear journalists, granite is not formed on dry land, as plutonic rocks crystallize in the underground). Already Alfred Wegener demonstrated that continents can’t simply sink, as granite has a lower mass density (2,7g/cc) it will “float” on the denser mantle materials (3g/cc).

However in past centuries lost continents were at least a geological possibility.

In the 19th century naturalists realized that many similar animals were distributed on different continents or remote islands. For short distances this was explainable by (voluntary or involuntarily) migration across the sea by “hopping” from island to island, but many distances were too great for large terrestrial animals, especially for mammals.

The British lawyer and zoologist Philip Lutley Sclater (1829-1913) noted the particular distribution of a particular group of primates – the Lemurs. Sclater however included in his Lemuridae more species than modern zoologists – the Lemurs, the Indri and the Aye-aye (found on Madagascar and shown above in a figure from SCLATER 1899), the Galagos (found in Africa), the Loris (found in Asia) and the Tarsiers (found in Indonesia). He observed that “while 30 different species of Lemurs are found in Madagascar alone, all of Africa contains some 11 or 12, while the Indian region has only 3.” In a short essay of 1864 titled “The Mammals of Madagascar“, published in the “The Quarterly Journal of Science“, he provided a possible answer – Madagascar, with it’s rich diversity of species, was the primordial homeland of lemurs which spread all over Asia and Africa by a land bridge connecting once these continents – he speculated even on a connection to America. He named this supposed land bridge/continent appropriately “Lemuria“.

“The anomalies of the Mammal fauna of Madagascar can best be explained by supposing that anterior to the existence of Africa in its present shape, a large continent occupied parts of the Atlantic and Indian Oceans stretching out towards (what is now) America to the west, and to India and its islands on the east; that this continent was broken up into islands, of which some have became amalgamated with the present continent of Africa, and some, possibly, with what is now Asia; and that in Madagascar and the Mascarene Islands we have existing relics of this great continent, for which as the original focus of the “Stirps Lemurum,” I should propose the name Lemuria!“

In later works he was more cautious:

“This fact would seem to show that the ancient “Lemuria”, as the hypothetical continent which was originally the home of the Lemurs has been termed, must have extended across the Indian Ocean and the Indian Peninsula to the further side of the Bay of Bengal and over the great islands of the Indian Archipelago.”
SCLATER & SCLATER (1899): “The Geography of Mammals.”

Sclater was not the first to promote ancient land bridges or even a sunken continent  in the Indian Ocean, as the idea of oceans as drown landmasses was a plausible geological theory at the time.

The French geologist Etienne Geoffrey Saint-Hilaire had speculated about a connection between Madagascar and India in 1840, the English geologist Searles V. Wood (1830-1884) hypothesized the existence of a giant southern continent during the “secondary era” (our Mesozoic). Alfred R. Wallace (1823-1913) proposed in 1859 a sunken continent to explain the fauna found on the island of Celebes, but became later one of the most eloquent critics of the theory of sunken landmasses.

In 1868 the German biologist Ernst Haeckel published his “Natürliche Schöpfungsgeschichte“ (The history of Creation), addressed to a general public where he promoted his view of evolution. Haeckel considered the earliest humans descending from Asian primates and placed the cradle of humanity in Asia, Africa and very cautiously on the hypothetical island between these two continents. Lemuria played a major role as possible migration route of humans into Africa and Indonesia.
In later editions and the English version of the book, translated by Ray Lankester in 1876, the supposed continent is even emphasised and labelled in the map as “Paradise” and displayed as cradle of humanity.

“The primeval home, or the “Centre of Creation”, of the Malays must be looked for in the south-eastern part of the Asiatic continent, or possibly in the more extensive continent which existed at the time when further India was directly connected with the Sunda Archipelago and eastern Lemuria.”
HAECKEL (1876): “The history of Creation.“

Fig.2. and 3. Ernst Haeckel, “A hypothetical sketch of the monophyletic origin and extension of the twelve races of Man from Lemuria over Earth”, from “Natürliche Schöpfungsgeschichte”, Plate XV. Note the differences in the German version (1868) without Lemuria and the English version (1876) with Lemuria, after 1870 Haeckel adopted and promoted the idea of a sunken continent in the Indian Ocean (image in public domain).

“The probable primeval home or “Paradise” is here assumed to be Lemuria, a tropical continent at present lying below the level of the Indian Ocean, the former existence of which in the tertiary period seems very probable from numerous facts in animal and vegetable geography. But it is also very possible that the hypothetical “cradle of the human race” lay further to the east (in Hindostan or Further India), or further to the west (in eastern Africa).”
HAECKEL in 1870.

Haeckels work, as vague at is was, however spread the idea of sunken continents to a larger public, still in 1919 the British author Herbert George Wells wrote:

“We do not know yet the region in which the ancestors of the brownish Neolithic peoples worked their way up from the Palaeolithic stage of human development. Probably it was somewhere about south-western Asia, or in some region now submerged beneath the Mediterranean Sea or the Indian Ocean, that, while the Neanderthal men still lived their hard lives in the bleak climate of a glaciated Europe, the ancestors, of the white men developed the rude arts of their Later Palaeolithic period.”
WELLS (1919): “Outline of History.“

The idea of Lemuria, as lost cradle of humankind, was too intriguing for pseudoscientific and esoteric groups and authors not to be incorporated in their worldview.
In 1888 the Russian medium Elena Petrovna Blavatskaja (1831-1891), strongly influenced by Asian philosophy, published her book on “The secret doctrine“, in which she proposes Lemuria as the cradle of one of the seven races of humanity. These beings supposedly possessed four arms and eyes and were egg-laying hermaphrodites, sharing Lemuria with dinosaurs. The mythical Lemuria became part of popular culture…

Bibliography:

RAMASWAMY, S. (2004): The lost land of Lemuria – Fabulous geographies, catastrophic histories. University of California Press: 334

The movie combines the western-genre with the classic monster-movie of the sixties and seventies – however the movie was released at the end of the golden age of monster-movies and the public had almost lost interest in this genre. The particular storyline of “The Valley of Gwangi“  was intended to attract fans of monster-, but also adventure-, catastrophe- and western- movies.

Ray Harryhausen will be remembered for his many stop-motion creatures crawling, stomping and running through countless adventure, science-fiction and fantasy movies – in the years 1938 – 1940 Harryhausen worked even on a “science-movie” -  called “Evolution“, featuring -what else – prominently stop-motion dinosaurs…

*This image is the cover of a videotape, DVD, Blu-ray Disc, etc. and the copyright for it is most likely owned by either the publisher of the video or the studio which produced the video in question. It is believed that the use of low-resolution images of video covers qualifies as fair use under United States copyright law.

Fig.1. Lithograph by Joseph Nash depicting the official opening at Crystal Palace, with the royal family presiding (Image in public domain, from the blog “Love in the Time of Chasmosaurs“).

Inside Crystal Palace the “very best that human ingenuity and cultivated art and science could inspire” was displayed to the curious public. One of the organizers and judges of the spectacle was 47 year old anatomist and palaeontologist Richard Owen, very busy supervising the zoological and botanical exhibitions, entertaining guests and awarding medals to the most spectacular curiosities.
Hiding in the crowds was another self-educated palaeontologist, 61 year old Gideon Mantell, who had made his way to London despite a severe and very painful injury of the spine. He remembers in his diary:

“The effect is indescribably overpowering. I cannot express the effect it has left upon my mind; nothing can prepare you for this.“

Mantel was enthusiastic about the new presented scientific tools, like telescopes, mechanical clocks and microscopes, but admired also the collection of geological specimens:

“I managed to squeeze into the back and least crowded compartments of minerals and with some difficulty ascended the gallery overlooking the transept to look down on the sea of heads underneath.“

The World’s Fair closed October 15, 1851. It was decided to relocate the Crystal Palace on Sydenham Hill, in suburb southern London, and a part of the permanent park should be devoted to geology and palaeontology.
In summer 1852 Mantell, discoverer of many fossil bones of prehistoric reptiles, was contacted by the Crystal Palace Company to discuss an ambitious project:

A “Geological Court [to] be constructed, containing a collection of full-sized models of the animals and plants of certain geological periods, and that Dr. Mantell be requested to superintend the formation of that collection.“

Here was finally a chance for Mantell to present his discoveries to a larger public, however he realized that his bad health would prevent him to finish the project – and he refused. November 11, 1851 Mantell died due an overdose of opiates.

Under the severe examination of Richard Owen soon the first models of all known giant lizards of the time – Ichthyosaurus, Plesiosaurus, Pterodactyls and the dinosaurs Megalosaurus, Iguanodon and Hylacosaurus (today referred as Hylaeosaurus) were completed.
Owen reconstructed the Iguanodon and the other dinosaurs as large, quadruped rhinoceroses, ignoring the observations of Mantell, who noted that the forelegs of the Iguanodon are smaller than the hind legs and the animal was more likely a (sort of) biped reptile.

Fig.2. An illustration by artist Benjamin Waterhouse Hawkins, published in 1854 in an article titled “On visual education as applied to geology” and dedicated to the reconstructions of Crystal Park. The various animals are arranged in their chronostratigraphic order (emphasized also by the geological section in the background), from right (oldest) to left (youngest) (image in public domain).

The life sized models of Crystal Palace inspired the very first “Dinomania“- hundreds of thousands of people visited the Crystal Palace creatures, dinosaurs were discussed in popular magazines and models, posters, poems and novels of prehistoric beasts were widely distributed and appreciated – to the great delight of cartoonists:

Fig.3. “The Effects of a Hearty Dinner after Visiting the Antediluvian Department at the Crystal Palace”, a cartoon published in the magazine Punch in 1855 (image in public domain). An unsuspecting visitor of the Crystal Palace exhibition is haunted in his nightmares by the monstrosities emerging from the distant (and not so distant) past.

Bibliography:

CADBURY, D. (2010): The Dinosaur Hunters. A true Story of Scientific Rivalry & the Discovery of the Prehistoric World. Fourth Estate Publisher: 386
RUDWICK, J.S.M. (1992): Scenes From Deep Time – Early Pictorial Representations of the Prehistoric World. The University of Chicago Press, Chicago – London: 280

“Surface conditions on Earth, have been for most of geological time regulated by life…[]…This new link between Geology and Biology originated in the Gaia hypothesis”
NASA geologist Paul Lowman (2002)

In 1965 James Lovelock, inspired by research on the habitability of Mars, proposed in a Nature-article to consider the various spheres of earth (lithosphere, hydrosphere, biosphere and atmosphere) as an interconnected, self-regulating system. He followed the suggestions by novelist William Golding and named this idea the controversial Gaia-hypothesis, after the ancient  titan Gaia – the personification of earth.
Lovelock argued that biotic and abiotic processes limit the possible amplitude of changes of terrestrial conditions – like the salinity of the oceans, the surface temperature and the atmospheric chemistry – therefore forcing earth into a life-supporting disequilibrium between two stable extremes, the frozen wasteland of Mars and a greenhouse hell of Venus.
In 1971 microbiologist Lynn Margulis (1938-2011) joined Lovelock (here an interview with both scientists in 2011), emphasizing the link between geology and biology for the Gaia-hypothesis.

“Some 30 million types of extant organisms have descended with modification from common ancestors; that is, all have evolved. All of them-ultimately bacteria or products of symbioses of bacteria – produce reactive gases to and remove them from the atmosphere, the soil, and the fresh and saline waters. All directly or indirectly interact with each other and with the chemical constituents of their environment, including organic compounds, metal ions, salts, gases, and water. Taken together, the flora, fauna, and the microbiota (microbial biomass), confined to the lower troposphere and the upper lithosphere, is called the biota. The metabolism, growth, and multiple interactions of the biota modulate the temperature, acidity-alkalinity, and, with respect to chemically reactive gases, atmospheric composition at the Earth’s surface.“

However the general notion that the Gaia-hypothesis states that “earth as a living planet” or a “life form” in the sense of entity is incorrect.
Organism do not manipulate deliberately the system so it can support them; however if an organisms harms his environment (and the life-supporting properties) it eventually will be naturally selected from the system. Fortunately environments can also tolerate some degree of change without losing their life-supporting properties.

The legacy of the Gaia-hypothesis is the consideration to see geology as one of the Earth System Sciences and appropriately to consider what we call “Earth” as the result of “elegant truths; of exquisite interrelationships; of the awesome machinery of nature.” (Carl Sagan in episode 1 of Cosmos “The Shores of the Cosmic Ocean”, 1990)

Bibliography:

MARGULIS, L. (2004): Gaia by Any Other Name. In (ed.), Schneider S.H.: “Scientists Debate Gaia – The Next Century”: 7 – 12

October 1800 two ships – the “Geographe” and the “Naturaliste” – set sail from the harbor of Le Havre, France. Under the command of Captain Nicolas Baudin (1754-1803) geographers, astronomers, artists, naturalists, zoologists, botanists, and 2 mineralogists – Louis Depuch (1774-1803) and Charles Bailly (1777-1844) – were instructed to explore, map and eventually claim for France new territories of this new world. In the last moment also the young zoologist, and trained paleontologist, Francois Auguste Peron (1775-1810) joined the expedition.

The geological observations made by Depuch (died during the expedition) are known from various reports send to Baudin. Bailly will publish some notes after his return to France and Peron included his research in the official report of the expedition.

In May 27, 1801 the bare land of Cape Leeuwin was in sight and the naturalists went on land along the Wonnerup Inlet, where they collected the first specimens of Australian animals, plants and rocks.

Fig.1. The “Baudin” – expedition, route drawn on Louis de Freycinet´s (1779-1842) “Carte générale de la Nouvelle Hollande”, published in 1811 as part of the results of the 1800-1804 expedition (image in the public domain).

A storm forced the men to remain on land for several days and one man died during a failed attempt to reach the ships (during the entire expedition 32 men died, 13% of the crew, a surprising low percentage considering the period). The storm separated the two ships, the “Naturaliste” proceeded to the island of Timor, a Dutch colony at the time, where the crew fell ill with Malaria and other tropical diseases. The “Geographe” approached in November 1801 the island of Tasmania, where the expedition will stay for three months.
April 1802 the “Geographe” meet the British vessel “Investigator“. The expedition of the “Investigator” will map large parts of South-Australia and prove that Australia is one large continent, not two islands separated by a sea strait, as some geographers assumed. This was a disappointing discovery for captain Baudin, as there was no apparent geographic separation between the territories already claimed by British explorers, the entire continent had to be considered of British domain.

Captain Baudin, the crew and the naturalists could now only hope to gain some fame with the scientific results of the expedition.

Depuch and Bailly used a rock classification scheme, developed by the famous French geologist Déodat de Dolomieu, with four categories. They recognized primary rocks, such as granite; secondary rocks, such as stratified sandstone and limestone; alluvium (recent deposits) and volcanic rocks, such as basalt. The presence of these rocks in Australia was an important discovery, it proved that the classification scheme developed in Europe could be applied worldwide.

Fig.2. Charles-Alexandre Lesueur´s and Nicolas-Martin Petit´s depiction of Van-Diemen´s-Land for the “Voyage de decouvertes aux Terres Australes“. The two young men – unskilled workers at the beginning of the expedition -  were invited by Baudin to illustrate the logbook  -  both will become the most skilled artists for animal- and plantlife of the time. The granitic rocks found on the island of Tasmania convinced Peron and the other geologists that the most ancient – the primary – rock was Granite, forming the basement of all continents (image in public domain).

Peron noted along the west coast of Australia horizontal sand- and limestone layers (the Tamala-Limestone) and concluded, based on similarities to recent sediments, that these layers were deposited along an ancient beach, implying substantial variations in the sea level during geologic time:

“One of the greatest achievements of modern geology research and also one of its most indisputable, is the certain knowledge that, in the past, the level of the sea was higher than at the present time. At almost all places in the old and the new world is the proof of this phenomenon as numerous as it is evident. Only in les Terres australes was this still to be ascertained as, by virtue of its immense areal extent, it could have proved to be an important exception to the universality of the former domination of the ocean over the land.” (PERON & FREYCINET 1816)

Unfortunately the return to France will be disappointing for Peron. Captain Baudin dies on the island of Timor and French authorities will show little interest in the 220.000 samples of animals, plants and rocks, the 73 living animals, 3 kangaroos, 2 emus and 3 wombats brought back to Europe.
Peron publish his report “Voyage de decouvertes aux Terres Australes” only in  1807, after a long struggle for money and dies just three years later, before the completion of the second volume. However the sea shells collected during the expedition will be studied by an important French naturalist – Jean-Baptiste de Lamarck. In 1804 Lamarck publishes his theory about the transmutation of species, based in part of the observation that the fossil shells found in the sediments of France are similar, but not identical, to shells of living molluscs collected in Australia.

Fig.3. Peron discovers on the shores of Tasmania a living clam with a peculiar triangular shape – Trigonia antarctica – a genus of bivalve known only from fossils found in the sediments of the basin of Paris. He notes the similarities of this living specimen with fossil specimens – an important step to consider a relationship between fossil and extant species. Trigonia sp. from Cretaceous sediments of Bavaria.

Unfortunately for Lamarck – and the naturalists of the Baudin expedition – he mixed his careful observations with wild speculations. Lamarck noted variations of organisms in time, however he could not explain why such variations occur or why certain organisms went extinct or survived – apart invoking a final cause and implying a supernatural scheme. Geologist Charles Darwin will later regard Lamarck’s work as “useless“.

Bibliography:

GLAUBRECHT, M. & MERMET, G. (2007): Josephines Emu oder Die Geschichte einer vergessenen Expedition. GEO Nr.6/2007: 98-122
MAYER, W. (2008): Early geological investigations of the Pleistocene Tamala Limestone, Western Australia. from GRAPES, R.H.; OLDROYD, D. & GRIGELIS, A. (eds) History of Geomorphology and Quaternary Geology. Geological Society, London, Special Publications 301: 279-293
MAYER, W. (2009): The Geological Work of the Baudin Expedition in Australia (1801-1803): The Mineralogists, the Discoveries and the Legacy. Earth Sciences History Vol.28 (2): 293-324
RUDWICK, M.J.S. (2005): Bursting the limits of time – The reconstruction of Geohistory in the Age of Revolution. The University of Chicago Press, Chicago, London: 708

Fig.1. The infamous “Hydrarchos” by German fossil collector Albert Koch as displayed in New York. Not only was the fossil animal composed of various specimens of the extinct whale Zeuglodon, but in this illustration even the size of the supposed skeleton is exaggerated.  Image from FOWLER (1846): “The American Phrenological Journal and Miscellany”, image in public domain.

Like many other Victorian naturalists Lyell showed great interest in the supposed existence of large marine monsters. A good friend of Lyell, Canadian geologist John William Dawson, informed him of  a sighting in August 1845 at Merigomish, in the Gulf of St. Lawrence. Here two “intelligent” testimonies had observed a 100 foot long sea snake with humps on the back and the head similar to a seal. Lyell describes this sighting in his book “Second Visit to the United States of North America” (1849) and adds that stories about unusual encounters abound along the west coast of the U.S. He mentions even that a young sea serpent was still preserved in spirits in the Museum of New Haven. However Lyell, seeing the specimen for himself, agreed with other skeptics that it was nothing more than a land snake (Coluber constrictor) with a deformed spine.

Fig.2. Newspaper from Boston with an article about the strange, but true, encounter with the Mountauk Monster – a sea snake in 1817 (image in public domain).

Despite the lack of evidence, Lyell confess in his writings that he remained optimistic “for I believed in the sea serpent without having seen it.” Lyell’ s interest in sea snakes was strongly influenced by his passion for geology.

At Lyell’s time the age and destiny of earth was still a controversial topic. Most geologists assumed a gradual formation of earth, characterized by constant progress until the human epoch. In contrast Lyell postulated two important principles for geologic time – processes observable today were active also in the remote past and time is (similar to the motion of the stars) organized in cycles. Large marine reptiles (like the Ichthyosaur or Plesiosaur), but also large marine mammals (like the Zeuglodon), were known to have existed in the past. Their continuous existence would provide biological – and therefore independent – evidence for his geo-theory.
Assuming sea serpents were never captured alive in historic times as they were very rare and almost extinct, the supposed rise in population during the 19th century (as, so Lyell, this could explain the rise in sightings since 1817) was a result of  earth’s history repeating itself. The large prehistoric reptiles of the past, almost gone during the last ice age, would again rise to conquer the warming world.

Lyell was not the only geologist searching for the mythical sea snake. Many naturalists at the time considered (or explained) sea snakes as survivors of a former world. But Lyell was aware about the controversy surrounding the topic. In the end he never published sea snake accounts to support his geo-theory and probably it would do more harm than good to include sea snakes and other monsters in a textbook about geology.

Fig.3. The Ichthyosaurus, only to be found in the museum? The discovery of bones and description of prehistoric beasts boosted the sightings of supposed sea and lake monsters during the 19th century, caricature published in 1885 in the Punch magazine (image in public domain).

Bibliography:

CLIFFORD, D.; WADGE, E.; WARWICK, A. & WILLIS, M. (eds.) (2006): Repositioning Victorian Sciences – Shifting Centres in Nineteenth-Century Thinking. Anthem Press: 300
GLENDENING, J. (2009): ‘The World-Renowned Ichthyosaurus’: A Nineteenth-Century Problematic and Its Representations. Journal of Literature and Science. Vol.2 (1): 23-47
LYONS, L..S. (2010): Species, Serpents, Spirits, and Skulls: Science at the Margins in the Victorian Age. State University of New York Press: 260
SWITEK, B. (2010): Written in Stone – Evolution, the Fossil Record, and our Place in Nature. Bellevue Literary Press – New York: 320

Fig.1. This geological section, published in the book by German professor of geophysics August Sieberg “Einführung in die Erdbeben- und Vulkankunde Süditaliens” (1914), shows the anatomy of a stratovolcano, with a main conduit, various lateral dikes and a large sill connected to the magma reservoir. In contrast to the sketch, the conduits for magma are in reality only a few meters wide – too small for travel the Center of the Earth (image in public domain).

Since the 19th century many of Verne’s visions became true – humans visited the moon, submarines can travel under the sea and travels around the world are no longer a privilege for rich gentlemen – but what about the universe within earth?

The deepest natural cave known today is the Cave of Kruber (also Cave of Voronja), located in the Arabika Massif of the Gagrinsky Range of the Western Caucasus. This cave is explored to a depth of 2.191m, but possibly continues.
The deepest mines in the world are the TauTona and Savuka gold mines in the Witwatersrand region of South Africa, which are currently working at depths exceeding 3.900m.

In May 1970, to celebrate the birthday of Lenin, the former Soviet Union initiated the secret project “SG-3” on the Kola-Peninsula. The drilling project planned to study the Mohorovičić discontinuity, situated at a depth of 15 kilometers. Thee project continued until 1989, when technical and financial problems stopped the drill at 12.261 meters.
The United States initiated a similar ambitious project, but decided to drill the thinner oceanic crust (5-10 kilometers thick). Project Mohole started in 1961 and was abandoned in 1966, after recovering 170 meters long cores from the ocean floor in a depth of 3.500 meters. Modern commercial boreholes reach depths of 2.000-3.000 meters.

However even the Kola borehole covers just 0,2% of earth’s radius.

During a meeting of the International Association of Geologists in 2013 the chairman of the association, Dr. Abner Perry, lamented this fact “Well gentlemen, at one point at least I agree with Professor Christophe, the materials of the geologists are not charts, chalk and chatter, but the earth itself. We should never know the truth, until we are able to make that journey, and see for ourselves.“

Perry proposes the development and construction of a drilling machine to go to the earth’s core in this decade. Sourcing would be done by an anonymous US financier, however the association is now searching for brave “terranauts” willing to take the risk of this fantastic voyage. Interested candidates can read about the project following this link.

Fig.2. It´s hot, a lot of stress and a long journey to the center of the earth, but scientists are optimistic to discover new worlds underground.

Bibliography:

CARLSON, D.H.; PLUMMER, C.C. & HAMMERSLEY, L. (2009): Physical Geology – Earth Revealed. 9th ed., McGraw-Hill Publisher: 645
SCHICK, R. (2002): The Little Book of Earthquakes and Volcanoes. Springer/Copernicus Books, New York: 164

Based on his observations along the foothills of the Alps, Arduino recognized a stratigraphic column with 4 classes: unstratified or poorly stratified rocks (or “Primary Rocks“, survived into the 20th century as “Paleozoic“), stratified rocks (“Secondary Rocks“, or “Mesozoic“), more recent, as yet unconsolidated, sediments (“Tertiary Rocks“) and as own category volcanic rocks.

Fig.1. Arduino used this famous section of rocks exposed in the Val d´Agno to explain his classification scheme. The numbers refer to the thickness of the strata, the letters to the description in the accompanying text. The extremely tattered state of the original drawing suggests that Arduino demonstrated it repeatedly to the many naturalists who visited him (image in public domain).

Bibliography:

VAI, G.B. (2007): A history of chronostratigraphy. Stratigraphy Vol.4 No. 2/3: 83-97

William Smith, born March 23, 1769, introduced in his “Strata – Identified by organized Fossils” (1816) the “principle of faunal succession” into stratigraphy. Geological maps before Smith mapped and catalogued rocks based only on the inorganic properties, like chemical composition or colour. This classification was very restricted and confusing. Smith discovered and applied a classification scheme that can identify sedimentary rocks of the same age with almost no doubt.

“Fossils have been long studied as great curiosities, collected with great pains, treasured with great care and at a great expense, and shown and admired with as much pleasure as a child’s hobby-horse is shown and admired by himself and his playfellows, because it is pretty; and this has been done by thousands who have never paid the least regard to that wonderful order and regularity with which nature has disposed of these singular productions, and assigned to each class its peculiar stratum.”
William Smith (1796)

Using this principle he compiled one of the first “true” geological maps in history, useful also to track the – at the time of the Industrial Revolution – much valuable coal seams.

Map.1. “A Delineation of the Strata of England and Wales….” by William Smith (image in public domain). The colours are based on the colours of the mapped rocks, coal appropriately shown in black. However Smith uses the characteristic assemblages of fossils to further subdivide similar looking rocks – providing a valuable tool to show the stratigraphic order of the underground.

Bibliography:

WINCHESTER, W. (2001): The Map that Changed the World: William Smith and the Birth of Modern Geology. New York: Harper Collins: 352

The Scottish Maria Matilda Ogilvie Gordon (1864-1939, the photo shows her in 1900, image in public domain), or simply May, was the oldest daughter of a clergy family with eight children, five boys and three girls.
The parents valued education and maintained connections to various schools and colleges – Maria entered Merchant Company Schools’ Ladies College in Edinburgh at age of 9. Already in these early years she showed a profound interest in nature and during holidays she enjoyed to explore the landscape of the Highlands accompanied by her elder brother, the later geologist Sir Francis Ogilvie.

May aspired to become a musician and at age 18 she went to London to study music, becoming a promising pianist. However already in the first year her interest to nature prevailed and she decided for a career in science.

Studying both in London and Edinburgh she obtained her degree in geology, botany and zoology in 1890. Maria Ogilvie hoped to continue her studies in Germany, but in 1891, despite efforts and friends, even by the famous geologist Baron Ferdinand Freiherr von Richthofen (another pioneer geologist of the Dolomites), she was refused at the University of Berlin – as women were still not permitted to enroll for higher education in England and Germany. She went to Munich, where she was received friendly by eminent paleontologist Karl von Zittel (1839-1904) and zoologist Richard von Hertwig (1850-1927). In contrast mineralogist Paul Heinrich von Groth (1843-1927) refused to allow the young women to enter his laboratory. Maria Ogilvie was not allowed to enroll in a regular course of studies even at Munich, research was done as private person and to listen the lectures she had to sit in a separate room with the doors half-open.

July 1891 von Richthofen invited her to join a 5-week trip to the nearby Dolomites, visiting also the Gröden-Valley.
From the first day Maria Ogilvie was immensely impressed by the landscape. Richthofen introduced Maria into alpine geology and the party visited the meadows of Stuores in the Gader-Valley. At the time Maria Ogilvie had studied modern corals and was inclined to become a zoologist, but Richthofen, maybe also after showing her the beautiful preserved fossil corals of Stuores, advised her to become rather a geologist and to study and map this area.

Fig.2. View of outcrops with fossil-bearings marls of the Stuores.

Richthofen was over 60 years old and therefore he couldn’t provide much support in the field, Maria Ogilvie remembers in 1932 the challenges and dangers of field work, sometimes accompanied by a local rock climber named Josef Kostner:

“When I began my field work, I was not under the eye of any Professor. There was no one to include me in his official round of visits among the young geologists in the field, and to subject my maps and sections to tough criticism on the ground. The lack of supervision at the outset was undoubtedly a serious handicap.“

For two summers she hiked, climbed and studied various areas in the Dolomites and instructed local collectors to carefully record and describe their fossils.
In 1893 she published the results in the article “Contributions to the geology of the Wengen and St. Cassian Strata in southern Tyrol“. The article showed various hand-drawn figures of the Dolomites and provided important contributions to the, at the time still poorly know, stratigraphic record of these mountains, establishing marker horizons and describing the ecology of various fossil corals associations. Maria alone described 345 species (today 1.400 species are recognized) of mollusks and corals of the Wengen and St. Cassian Formations.
The published paper, extract of her thesis “The geology of the Wengen and Saint Cassian Strata in southern Tyrol“, finally earned her respect by the scientific community and more important: her Doctor of Science degree in 1893 from the University of London – the first female DSc in the United Kingdom.
The same year she returned into the Dolomites to proceed with her geological and paleontological research and in 1894 she published her second important contribution, the “Coral in the Dolomites of south Tyrol.” Therein Maria Ogilvie emphasized that the classificaton of corals must be based on microscopic examination and characteristics, not as usually done simply on superficial resemblance.

In 1895 she returned to Aberdeen, where she married a longstanding admirer, the physician Dr. John Gordon, husband who (unusual for the times) respected and encouraged her passion for the mountains. He and the four children accompanied Maria on various excursions into the Dolomites.

In 1900 she returned to Munich, becoming the first woman to obtain a PhD there. As thank to her old mentor, palaeontologist von Zittel, she translated his extensive German research on the “Geschichte der Geologie und Palaeontologie” into English as “The History of Geology and Palaeontology.“

Maria Ogilvie continued her studies and continued to publish, mostly privately. In 1913 she was preparing an ulterior important work about the geology and geomorphology of the Dolomites, to be published in Germany, but in 1914 with the onset of World War I and the death of the publisher the finished maps, plates and manuscripts were lost in the general chaos.
Like so many times before Ogilvie didn’t simply surrender. In 1922 she returned into the Dolomites, where she encountered the young paleontologist Julius Pia. Both became friends and in 1922 to 1925 they explored many times together the area.
She published papers on the tectonic evolution of the Dolomites and also books for the interested layman, hoping to share her fascination of the Dolomites with others – the first examples of modern geological guidebooks for this region.

Fig.3. and 4. Landscape profile (and recent photography) of the Langkofel-massif after a drawing from GORDON & PIA (1939): “Zur Geologie der Langkofelgruppe in den Südtiroler Dolomiten.”

To remember her contributions to paleontology in 2000 a new fossil fern genus, discovered in Triassic sediments of the Dolomites, was named after Maria Gordon – Gordonopteris lorigae.

Bibliography:

WACHTLER, M. & BUREK, C.V. (2007): Maria Matilda Ogilvie Gordon (1864-1939): a Scottish researcher in the Alps. In BUREK, C. V. & HIGGS, B. (eds): The Role of Women in the History of Geology. Geological Society: 305-317

Since prehistoric times humans ventured into caves, as proved by the discovery of rock art even in remote parts of many European cave systems. In historic times and in many cultures caves became mythological places or passages to the underworld. According to the Maya the karst caves of the Yucatan peninsula were the gates to Xibalba, or the “Place of fear“.  Also for the ancient Greeks the only access to the reign of the deaths was by cave entrances or sinkholes, presumably guarded by terrible demons.

A first naturalistic approach to caves and the deep underground was attempted during the Renaissance. The great German scholar Athanius Kircher (1602-1680) publishes in his “Mundus Subterraneus” (1665), a textbook on alchemy and geology, the description of large underground rivers and even lakes, feeding superficial springs. However he also notes that these hidden rivers are inhabited by dragons, giants and even unicorns.

In his “Itinera alpina” (“Voyage in the Alps“, (1702-1711) the Swiss physician and naturalist Johann Jakob Scheuchzer (1672-1733) explains caves and fissures formed by the selective erosion of rocks by percolating gas and water.

Fig.1. Johann J. Scheuchzer proposes in 1716 the existence of a primitive  hydrologic cycle. “Subterranean rivers” flowing in the underground connect superficial lakes with springs. This theory was based on the chemical properties of the spring water, often enriched with chemical elements. The water – so Scheuchzer – dissolves minerals from veins deep within the mountain and transports the elements to the surface.

The association of caves and water seems obvious, as many caves are in fact formed by dissolution of rocks like lime- and dolostone by water. Dana Hunter investigates this fascinating (and sometimes fatal) reaction between rocks and water in her post about karst and sinkholes in Florida.

During the 18th century caves were regarded mostly as curiosities and places for tourists. The serious study of caves came relatively late. One of the first naturalist studying caves in the U.S. was polymath Constantine Samuel Rafinesque-Schmaltz (1783-1840), who published in 1832 a description and classification of the caves of Kentucky. Thomas Jefferson made the first map of a cave in the U.S. (Madison’s Cave in Virginia) and in his “Notes on the State of Virginia” (1853) published various other maps of caves.

The demand for nitrates to manufacture gunpowder during the late 19th century and early 20th century was satisfied by the excavation of organic deposits preserved in caves, like Mammoth Cave in Kentucky. In 1878 cave diggers opened a passage into the Luray Caverns (Virginia) and Scientific American commissioned an article about the discovery to clergyman and amateur scientist Horace C. Hovey (1835 – 1913). Based on this and earlier cave explorations Hovey published in 1882 a highly influential book with the title “Celebrated American Caverns“. In response to Hovey’s stories about cave adventures many show caves were made accessible to the interested public and soon the exploration of the underground became a scientific discipline.

Fig.2. Nineteenth-century illustration on a postcard of Bottomless Pit at Mammoth Cave.

Bibliography:

HALLIDAY, W.R. (2006): America, North: History. In GUNN, J. (ed.) “Encyclopedia of caves and karst science”: 102-109
ROMERO, A. (2009): Cave Biology – Life in Darkness. Cambridge University Press: 291

Fig.1.The small republic of San Marino issued a series of nine values, showing a Brontosaurus, Brachiosaurus, Pteranodon, Elasmosaurus, Tyrannosaurus, Stegosaurus, Thaumatosaurus, Iguanodon and Triceratops -mostly in dull colors (all images are in public domain).

Fig.2. An interesting series of psychedelic postage stamps from Tanzania (1991), presenting the first (very) colorful dinosaurs.

Fig.3. Many editions of stamps with dinosaurs are intended for collectors – therefore often more aesthetic appealing as scientific accurate. Sometimes the motif is even simply copied from other artists or publications, like these two specimens, copies from the Saltopus by Jane Burton and the Tyrannosaurus by Doug Henderson.

Fig.4. The first postage stamps showing tracks of dinosaurs were released in Lesotho in 1984.

Fig.5. Evolutionary ladder in a Polish edition, illustrations by artist Andrzej Heidrich (he designed also advertising posters and Polish banknotes).

Fig.6. Not only “living dinosaurs”  – a German series (1990) celebrates with dinosaur-skeletons 100 years Museum for Natural History in Berlin.

Fig.7. The End…

Bibliography:

THENIUS, E. & VAVRA, N. (1996): Fossilien im Volksglauben und im Alltag – Bedeutung und Verwendung vorzeitlicher Tier- und Pflanzenreste von der Steinzeit bis heute. Senckenberg-Buch 71, Waldemar Kramer Verlag – Frankfurt am Main: 179

Darwin’s tree of life is rooted in deep time, from his notebook (1837), image in public domain.

Darwin is today remembered for his gradualistic view of earth’s history, an essential prerequisite for his view of life, as he concludes in 1859 ” from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” The famous voyage of the Beagle would prove decisive for Darwin to discover deep time and adopt this view.

The first stop of the H.M.S. Beagle in January-February 1832 was “Quail Island” (today Island of Santa Maria) – a small island located in the bay of Praia of the larger island of St.Jago (today Santiago). This visit is especially interesting as it provides some glimpses in Darwin’s geological background at the beginning of the Voyage of the Beagle (1831-1836) and his later “evolution” as geologist.
Darwin collected basic experience as geologist during a trip across Wales and surely know the geological theories of the time, especially regarding the formation and age of the earth. The notion of a 6.000 year old earth was already dismissed by scholars and even the interpretation of gravel and sand deposits as the remains of the biblical flood (the “Diluvium“) was questioned. However the notion of earth’s history of a succession of catastrophic events was still fiercely discussed.

Many geologists at the time proposed that geologic processes in the past differed significantly from recent processes; even certain types of rocks (and the formation of these rocks) were limited to certain time periods, when today unknown geological processes were shaping the earth. The lawyer Charles Lyell challenged this interpretation of earth’s history, arguing that common and slow processes still observable today also acted long time ago.

Captain FitzRoy offered Charles Lyell’s recently published and controversial “Principles of Geology” as welcoming gift, but Darwin probably didn’t find time to read the book in the first weeks of the expedition. His former mentor, botanist John S. Henslow, even “advised me to get and study the first volume of Principles, which had then just been published, but on no account to accept the views therein advocated.“

It’s therefore even more surprising to read in Darwin’s autobiography (1876-1881) the following phrase:

“The very first place which I examined, namely St. Jago, in the Cape de Verde islands, showed me clearly the wonderful superiority of Lyell’s manner of treating geology.”

Darwin also emphasises how the visit of St.Jago converted him to Lyell’s geology:

“The geology of St. Jago is very striking, yet simple: a stream of lava formerly flowed over the bed of the sea, formed of triturated recent shells and corals, which it has baked into a hard white rock.
Since then the whole island has been upheaved. But the line of white rock revealed to me a new and important fact, namely that there had been afterwards subsidence around the craters, which had since been in action, and had poured forth lava. It then first dawned on me that I might perhaps write a book on the geology of the various countries visited, and this made me thrill with delight. That was a memorable hour to me, and how distinctly I can call to mind the low cliff of lava beneath which I rested, with the sun glaring hot, a few strange desert plants growing near, and with living corals in the tidal pools at my feet.“

Darwin uses in later publications the similarity of the fossils found in the carbonate sediments (Darwin’s line of white rock) and the still living animals on the shore as evidence that no substantial change in the geologic processes forming these rocks occurred over time.

But from the geological notes he made during the field trip on St. Jago it emerges that young geologist Darwin was still struggling to accept this idea. More important, accepting slow geological processes made it necessary also to accept a very old earth.
During one of his daily excursions on St.Jago Darwin discovered a mature baobab (gen. Adansonia) tree growing on the bottom of one of the large valleys carved into the hard basaltic rocks of the volcanic island.

“In this [one of the valleys north of Praya] grows the celebrated Baobab or Adansonia; this tree only 45 feet high, measured two feet from the ground round the solid trunk. 35.-Some of the same species in Africa were supposed by Adanson to reach the enormous age of 6000 years.-The very appearance of the tree strikes the beholder that it has lived during a large fraction of the time that this world has existed.“

Darwin notes that a 6.000 year old tree would have experienced a significant period of earth’s history, implying that earth, despite older than proposed by scrupulous clergymen, would be not much older. However the eroded valleys in the thick lava shields, characterizing the landscape on St. Jago, need vast periods of time to form, as he continues:

“Of course the valley must be older & it is this one that has finally left the neighbourhood of Praya in the state we now find it.-How long a time intervened between this period and the deposition of former beach it is impossible to say.-during it three great phenomena occurred, the flowing of the lava.-the upheaving of the coast. & the great beds of diluvium collected in the older valley.-To what a remote age does this in all probability call us back & yet we find the shells [in the 'former beach'] themselves & their habits the same as exist in the present sea.“

In the final note Darwin considers the possibility that the similarity between the fossil shells and the recent ones could also be explained by a short interval of time between the formation of the white rock and the deposition of modern beach deposits (so there was no time for a faunal turnover).
However accepting a young age for the fossil beach deposits and the even younger eroded remains of the volcanic island of St. Jago (the coastal lava shields are covering Darwin´s white rocks and therefore according to stratigraphic principles are younger) would invoke some unknown – and presumably catastrophic – geological event in the not-too distant past to explain its actual deep incised valleys.

“I conceive it to be clear, from the pieces left standing and from the corresponding appearance on each side of the valley, that the country was originally covered with a uniform bed of this rock.-and that after being shattered by some great force: these valleys were formed by the agency of large bodies of water: To this latter force the valleys nearer the coast give abundant evidence.“

Darwin will admit in his diary “what a confusion for geologists.“

To be continued…

Bibliography:

CHIESURA, G. (2010): A Santiago sulle orme di Darwin. Darwin – Bimestrale di Scienze No.40: 32-36
CHIESURA, G. (2013): Isole di Darwin – Un curioso in mezzo al mare. CD-Rom
HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
JOHNSON, M.E.; BAARLI, B.G.; CACHAO, M.; da SILVA, C.M.; LEDESMA-VAZQUEZ, J.; MAYORAL, E.J.; RAMALHO, R.S. & SANTOS, A. (2012): Rhodoliths, uniformitarianism, and Darwin: Pleistocene and Recent carbonate deposits in the Cape Verde and Canary archipelagos. Palaeogeography, Palaeoclimatology, Palaeoecology Vol.329-330: 83-100
PEARSON, P.N. & NICHOLAS, C.J. (2007) : ‘Marks of extreme violence’: Charles Darwin’s geological observations at St Jago (Sao Tiago), Cape Verde islands. in WYSE JACKSON, P. N. (ed.) Four Centuries of Geological Travel: The Search for Knowledge on Foot, Bicycle, Sledge and Camel. Geological Society, London, Special Publications, 287: 239-253

The Scaglia Variegata and Scaglia Cinerea are two geological formations deposited during the late Eocene and early Oligocene (36 and respectively 33 million years ago). This period of transition is characterized by profound climatic changes and a biological crisis at a global scale. In less than a million years about 20% of genera of marine organisms became extinct. The causes of this mass extinction are not yet entirely clear. The gradual hypothesis invokes the slow drift of continents (especially the drift of Antarctica to the South Pole and subsequent global cooling effect) and the resulting climatic and environmental changes; the catastrophic hypothesis invokes the impact of a meteorite as the main cause of the sudden biological crisis.

In fact two very large impact craters are dated into the Eocene: Chesapeake Bay (located in North- America) and Popigai (Siberia). Popigai Crater is with a diameter of 100 km one of the largest impact craters on our planet (and the largest formed in the last 65 million years), followed by the 85 km large Chesapeake Bay Crater.

Some clues to solve the mystery about the biological crisis at the end of the Eocene are found in the sediments exposed in the quarry of Massignano, named after a small village near the Italian city of Ancona.

Fig.1. The Eocene-Oligocene transition in the quarry of Massignano (Marche – Italy), above sediment bed 17 (top of the quarry).

At the base of the outcrop with the Scaglia Variegata and Scaglia Cinerea formations two thin layers have been identified, characterized by abnormal concentrations of the element Iridium and the isotope Helium-3. Both substances are depleted in the rocks of earth’s crust, but quite concentrated in extraterrestrial material. These layers also contain spherules of the minerals spinel and quartz, displaying a lamellar and shattered structure. Such grains can be formed only by high temperatures and high pressure as experienced during an impact.

It seems almost certain that two objects of  extraterrestrial origin hit earth during the transition from the Eocene to the Oligocene, but it appears also that the effects of both impacts on terrestrial ecosystems were very limited. Complicating the question how large impacts affect the life on earth are also temporal uncertainties. According to some dating results the two mentioned impacts do not coincide with the Eocene extinction phase (between 37 to 38 million years ago) or the Eocene-Oligocene boundary (35,5 to 36,0 million years ago), but occurred 1 to 2 million years before and respectively after these periods.

Fig.2. “Raup´s Kill Curve”, named after paleontologist David M. Raup. The “kill curve” (blue) of RAUP 1991 was originally fit to the Cretaceous – Palaeogene impact data (60% of species wiped out with the Chicxulub crater of about 180 kilometer in diameter), and it predicted that much smaller impacts should cause significant extinctions. However, when the late Eocene impacts (which caused almost no extinctions) are plotted, the “kill curve” takes a different, S-like shape, and suggests that only the impacts above a certain threshold value have the potential to cause mass extinctions. But even one of the best studied event – the Chicxulub-impact – is not unequivocal.

Bibliography:

PROTHERO, D. (2006): After the Dinosaurs: The Age of Mammals (Life of the Past). Indiana University Press: 384

“A map is always a decisive criterion of they who aspire to the rank of geologists [E]very one who has not compiled a map, wants the necessary talent of combination . The spirited Darwin, with all his remarkable vivacity of mind, is for me no Geologist, only an able history maker of what nature as he believes, has done, and what never she did… This man could never make a tolerable geological map.”
Geologist Leopold von Buch* in a private letter to colleague Roderick Impey Murchison (1846)

In 1831 Charles R. Darwin attended a life changing expedition – not considering the voyage on board of the “H.M.S. Beagle“. The botanist John Stevens Henslow introduced the 22-year old Darwin to 46-year old Adam Sedgwick, self-educated naturalist and professor for geology and botany at Cambridge University. Even if Darwin was a student at Cambridge, he seems not to have attended Sedgwick´s lectures on geology, as he regrets in an autobiographic note that

“Had I done so I should probably have become a geologist earlier than I did.“

At the time Sedgwick was studying the geology of Wales and invited Darwin to join him at a field trip from Shrewsbury, Darwin’s hometown. Sedgwick was especially interested in the stratigraphic succession exposed in North Wales (Sedgwick will later use his observations to define the geologic epoch of the “Cambrian“), Darwin was interested to acquire the basics of geological field work. Darwin wrote in July to a friend

“I am now mad about Geology & daresay I shall put a plan which I am now hatching, into execution sometime in August, …[]“

Darwin was well equipped for his geological field investigation. He purchased a new clinometer with an incorporated compass for structural analysis and a geological hammer for the collection of rocks.
He visited Llanymynech (located west of Shrewsbury) alone and started to colour a map, mapping outcrops of sandstone and coal measures.

Sedgwick arrived to Shrewsbury on the 2nd August, visiting in the next days some outcrops located south-west of the city, where he recognized limestone and volcanic rocks. It’s not clear if he met Darwin already, for sure both geologist left Shrewsbury on 5th August venturing north. They spend a week trying to find Old Red Sandstone. Sedgwick was interested in the geological formations underlying the Old Red Sandstone (Silurian to Carboniferous in age), as the age of these rocks was still unknown and according to the large-scale geological map published by George Greenough in 1819 such rocks should be found in the area. However despite their combined efforts and a meeting in Llangollen with another great geologist, Robert Dawson, no Old Red Sandstone was found.

In his autobiography Darwin affirms that he left Sedgwick at Capel Curig, however it seems reasonable to assume that he visited with Sedgwick the island of Anglesey and even made a short trip to Dublin (as Sedgwick did, on Anglesey he found also the Red Sandstone he was after). During his voyage on the Beagle, Darwin will recognize on the Cape Verde Islands Serpentine, this kind of rock he could have only previously seen on Anglesey.

Fig.1. Geology of North Wales, after Reynolds 1860, 1889, Woodward 1904 (click to enlarge), with the route of Darwin and Sedgwick after ROBERTS 2001. The first part of the route, starting from Shrewsbury, follows the contact of the Silurian limestone (pink-coloured) and younger sediments (blue colour; Carboniferous to Permian), as both geologist hoped to find the Old Red Sandstone formation. Sedgwick found it (dark-orange) only on the island of Anglesey (original map in public domain).

Twenty pages of notes made by Darwin during this tour are still today conserved – in his autobiography he will later remember: “This tour was of decided use in teaching me a little how to make out the geology of a country…”
When Darwin returned to Shrewsbury on 29th August, a letter from Captain Robert FitzRoy was offering him a position as gentlemen companion on board of the Beagle. The rest is history…

*It seems as von Buch didn’t appreciate Darwin’s later publication on the volcanoes he visited during his voyage, where he rejected von Buch’s theory on the origin of volcanoes.

Bibliography:

HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
ROBERTS, M. (2001): Just before the Beagle: Charles Darwin’s geological fieldwork in Wales, summer 1831. Endeavour Vol. 25(1): 33-37

Biogeomorphology, also referred as ecogeomorphology or sometimes as zoogeomorphology, is the study of the linkages between ecology and geomorphology, or in simple terms between life forms and landforms. Such two-way interactions range from simple tracks left by an organism in the landscape to the complex cycles of energy and matter transfer (like for the element carbon) between the biosphere and the lithosphere.

The role of animals in the evolution of a landscape is still poorly studied, but one of the most interesting processes modifying a landscape involves digging animals.
Mammals move earth for two reasons – to collect food (digging up roots or other animals) or to dig a burrow as shelter. Large rodents, like the groundhogs (genus Marmota), are feared for their burrowing habits in agricultural areas, as the entrance to – or the collapse of – their extensive burrow systems can pose a hazard for the machinery or the livestock.
The density of burrows varies with the climate and environment, for example a humid mountain area can provide more food and guarantee the survival of more individuals than a dry steppe.
The increased activity of a large number of marmots can influence the surface runoff and erosion of a mountain slope and redistribute humus, moisture and mineral components in the soil profile. The research by Tadzhiyev & Odinoshoyev (1978) “Influence of marmots on soil cover of the eastern Pamirs” on the digging capacity of red marmots showed that they could move almost 28 cubic meter (that´s almost the load of a medium-sized truck) of earth per hectare (100 x 100 meter) in a single year. This suggests that on local scale marmots and relatives can play a role as geomorphologic factor.

Bibliography:

BUTLER, D.R. (2009) Zoogeomorphology – Animals as Geomorphic Agents. Cambridge University Press: 239
GOUDIE, A.S. (ed) (2001): Encyclopedia of Geomorphology Volume 1 A-I. Routledge, Taylor & Francis Group, London – New York: 1156

The debate over the age of the earth generated an even more intriguing question: how old is humankind? Written records date back some thousands of years, but geological evidence and the fossil record show us that earth must be millions of years old. Some authors tried to reconcile this discrepancy by assuming a succession of worlds, each destroyed by a global catastrophe. Therefore the “age or reptiles” could be very ancient, the ice age mammals more recent and the final catastrophe, creating the human world, happened probably only some thousands of years ago. This succession of worlds seemed to be in accordance both with the geological record as with the biblical chronology.
The discovery of stone tools made by humans in layers also containing fossils of extinct animals – and therefore inhabitants of a world older than the supposed biblical deluge – was met with incredulity.

In 1837 the French physician Casimir Picard (1806-1841) excavated various fossil sites near his hometown of Abbeville, where he recovered stone tools and bones of antediluvian beasts. He published his discoveries in 1838-1840, just shortly before his death. Another amateur – Jacques Boucher de Perthes (1788-1868) – continued Picard´s work and discovered the jaw of a fossil elephant near a man-made flint-axe.
Most authors dismissed these discoveries arguing that this association was the result of taphonomic processes, as bones and tools became mixed together by agents like water, animals or even modern humans. Some authors even considered all the discovered human fossils as fakes.
The most compelling evidence to support the antiquity of man was collected in 1858 during excavations in Windmill Hill Cave near the city of Brixham (Devonshire, England) by William Pengelly (1812-1894), a self-educated archaeologist. The cave was found untouched, the entrance sealed off by debris and stalagmites, proof that no living thing had entered the cave for thousands of years. Most important, the excavations were done by geologists, following the principles of the young science of stratigraphy.

Every uncovered layer of the floor of the cave was carefully mapped and the location of the fossils (bones of elephant, lion, bear and reindeer) and stone tools registered.

In the same period similar discoveries were made in France. In 1867, during the universal exposition in Paris , Édouard Lartet (1801-1871), a French lawyer, presented stone tools found in sediments and caves of the valley of the Vèzère. The most intriguing artifacts were bones with engravings of ice age animals – evidence that prehistoric men met these animals.

Fig.1. Ancient rock carving, collection of the museum in Les Eyzies-de-Tayac-Sireuil, valley of the Vèzère.

Finally in 1861, influenced by Charles Darwin’s explanation of the natural origin of all species on earth (including humans), eminent geologist Charles Lyell will publish “The Geological Evidence of the Antiquity of Man…[]” and establish the ancient origin of humankind as scientific fact.

Bibliography:

COHEN, C. (1998): Charles Lyell and the evidences of the antiquity of man. In: BLUNDELL, D.J. & SCOTT, A.C. (eds) Lyell: the Past is the Key to the Present. Geological Society, London, Special Publications, 143: 83-93
LYELL (1863): The Geological Evidence of the Antiquity of Man, with Remarks on Theories of the Origin of Species by variation.
PRESTWICH, J. (1860): On the occurrence of flint implements, associated with the remains of extinct mammalia, in undisturbed beds of the late geological period. Proceedings of the Royal Society of London, 10: 50-59
RUDWICK, M.J.S. (2008): Worlds before Adam – The Reconstruction of Geohistory in the Age of Reform. The University of Chicago Press: 614

Born into a relatively wealthy fisherman and trader family from the village of Denisovka (North Russia) he got interested in natural science in early years accompanying his father on trading missions. With nineteen he fled from his family and went to Moscow to inscribe into the Slavic Greek Latin Academy by falsely claiming to be a priest’s son. Despite financial problems and advanced age he exceeded into his studies and in 1736 he was granted an application for the University of Magdeburg. In the years 1739-1740 he studied mineralogy, metallurgy, and mining in the city of Freiberg (Saxony), one of the most important mining centers at the time. In 1741 he returned to Russia, where he helped to establish the Russian Academy of Science and Moscow State University. Today Lomonosov is considered one of the founding fathers of Russian sciences.

Lomonosov´s role in the history of geology is however still poorly studied, in part due the long decades of political isolation of the former Soviet Republics, in part due the language barrier and inaccessibility of his original texts to western historians and geologists.

With the special paper No. 485 by the Geological Society of America, Stephen M. Rowland and Slava Korolev (University of Nevada) provide a modern translation of Lomonosov´s “On the Strata of the Earth” – a 186 paragraph long appendix introducing basic concepts of physical geography and stratigraphy, intended to be used with a monographic work of mining and metallurgy industry, published in 1763, just two years before Lomonosov ´s early death.

“What a grand enterprise it would be to penetrate into the depths of the Earth with one’s mind, where our hands and eyes are forbidden by nature to go, to wander trough the subterranean world in one’s meditations, to penetrate by thoughts into narrow clefts, and to bring objects and processes out from the obscurity of eternal night into the sunlight of human understanding.“

Lomonosov poetic language should not distract from the practical use of his work, as he describes the distribution of precious metals or coal as results of physical processes and “tectonic” forces. Understanding these processes, so he explains, increases significantly the probability to discover and exploit such mineral deposits.

“Searching for stones without testing what you find is boring and not very productive“

It is interesting to note that Lomonosov discusses the formation of soils as results of physical processes acting over long periods of time. Such thoughts predate those of James Hutton‘s dissertation on the regeneration of eroded soils by almost 20 years.

“And so, there is no doubt that black soil is not primordial matter, but that it has been produced by the decomposition of animal and plant bodies over time.“

In a time when the age of earth was still a matter of wild speculations, Lomonosov argues, based on astronomical irregularities of the axis of the earth, that earth must be at least some 100.000 years old.

Also other important ideas, promoted later by Hutton and Victorian geologists, can be found in Lomonosov´s work.

“Now we must penetrate farther into the Earth’s interior, as deeply as our diligence permits us to travel“

He describes the metamorphic origin of some rocks by deposition, chemical alteration and finally transformation by heat and pressure. He recognizes volcanoes as important features, shaping entire landscapes. However he considers them products of burning materials distributed in earth’s crust, following the traditional view of earlier Renaissance scholars.

I know (as probably most geologists do) of Lomonosov only as an unusual underwater ridge was named in his honour in 1948. However the now available translation of “On the Strata of the Earth” introduced me to a fascinating man and scholar, which ideas, contributions and role for the development of geology must be reconsidered, also outside Russia.

Bibliography:

ROWLAND, S.M. & KOROLEV, S. (2012): On the Strata of the Earth – A Translation of О Слояхъ Земныхъ; by Mikhail Vasil’evich Lomonosov. Geological Society of America Special Paper 485: 41

DISCLAIMER: This review is based on a copy of “On the Strata of the Earth – A Translation of О Слояхъ Земныхъ“ kindly provided by Mr. L. April and Mr. M. Hudson of the GSA; However I have no affiliation with the publisher or author; the review reflects my personal opinion on the discussed book.

Image Copyright GSA, used here under Fair Use conditions for review purpose.

Fig.1. General view of the valley of Cordévole with the village and lake of Alleghe, on the left of the mountain Piz the scar of the landslide is barely visible in the forest, in the background the Civetta (3.220m).

The Alps-traveler Belsazar Hacquet (1739-1815) remembers a visit to the lake in 1780:

“The river Cordévole became my guide, by following him I would find the valley of Cadore. But only after some hundred steps the river was flowing in a large lake, existing here only for the last nine years. I walked around in eastern direction, to the villages of Sternade and Saviner until the mountain of Piz. First the lake was narrow, only by Saviner it became more than 100 venetian fathom [an old length unit used in the mining industry of these times, one fathom ca.1,8m] broad and more than thirty deep.
The last mentioned village once was situated on a hill, before it in a broad valley there were four smaller villages…[]…which became flooded by the lake, but the fourth locality, named Marin, was buried with the village of Riete under the collapse of the mountain of Piz, last mentioned village situated previously on the top of the mountain.”
Standing on the top of the mountain, I immediately noted that the mountain has a volcano on top of it, and it was possible to see how deep it went. After the mountain collapsed, it could be seen that its base was composed of limestone, build up by mighty layers, dipping from the west to the east with 45 degrees. The surface of the collapse is so plain, that a man has difficulties to climb on it to the mountain.“

Fig.2. Historic depiction of the landslide-lake in the “Atlas Tyrolensis” of 1774 by Peter Anich and Blasius Hueber. Note the boulders on the southern shore of the lake, Anich and Hueber were one of the first cartographers to use signatures to display geomorphologic features in their maps (image in public domain).

The strange notion by Hacquet of a historic volcano in the Dolomites is based maybe on his discovery of volcanic rocks in the area, however – as we today know – these deposits are more than 235 million years old. At the time of Hacquet’s geologic investigation volcanic forces were also believed to cause strong and sudden movements of the terrestrial surface, effects that maybe could also explain a sudden disaster, like a landslide. Notable how Hacquet describes the surface where the landslide “slipped away”.

The landslide of Alleghe killed 48 people and destroyed parts of the village of Riete and some farm buildings. The landslide-lake inundated the village of Peron. Only in February 1771 a new river channel formed and so the lake as we today can admire it was finally grown up.

Bibliography:

HÖFLER, H. & WITT, G. (2010): Katastrophen am Berg – Tragödien der Alpingeschichte. Bruckmann Verlag: 144

The letter contained an 20 pages long article entitled “On the Tendency of Varieties to Depart Indefinitely from the Original Type” – presenting some concepts that maybe could explain the biodiversity and peculiar geographical distribution of related species on the islands of Indonesia. The author argued that if in an inhomogeneous population only some specimens, with certain characteristics,  survive, these characteristics tend to become more common and more pronounced, until we would classify the modified specimens as a new species.
The author of the letter, send to gentleman geologist C. Darwin, was a certain Alfred Russel Wallace, a self-educated naturalist born January 8, 1823 in the Welsh town of Usk.

Fig.1. A.R. Wallace during his expedition to Singapore in 1862 (image in public domain).

Wallace discovered his passion for botany and natural sciences as young man and working as surveyor and teacher he saved some money for a planned expedition to South America. The expedition lasted from 1848 to 1852. In four years he collected an incredible variety of plant and animal species, intended to be sold to rich collectors and museums back in England. He also planned to publish his notes and observations.
But then the disaster, the steamer “Helen“, on which he was returning back home, caught fire and sank in the North Atlantic. Wallace was able to save only some drawings of plant- and fish-species. He had lost almost everything – his collection and so his income, most disappointing all his scientific notes and the hope to achieve some fame as naturalist. Only the sum paid by his insurance saved him from the financial ruin. He published a summary of his journey, but due the lack of exact information the book was not received well by the scientific establishment.

Wallace swore never to travel again, but in April 1854 he arrived to Singapore, ready again for an expedition that this time would last for eight years. During this expedition Wallace collected 125.660 specimens of plants and animals and discovered 1.500 new species of insects and birds. He will publish his results, adventures and observations in the acclaimed book “The Malay Archipelago“.

Fig.2. Between 1854 and 1862  Wallace explored almost the entire Indonesian archipelago, travelling for more than 22.000 km.

One of his most important discoveries resulted in part by his bad luck with ships. January 1856 Wallace missed the ship to Sulawesi. After waiting for four months in Singapore, he decided to make a detour on the islands of Bali and Lombok. Here Wallace noted something important, as the species of animals and plants differ significantly on the two islands, even if the islands are separated only by a narrow strait of sea. In fact he will later emphasize that the fauna differs more than the fauna of the British Islands if compared to the Japanese Islands! He will describe these two distinct faunal communities – on the one side the continent of Asia and islands dominated by tigers, rhinos and primates and on the other side Australia and islands characterized by kangaroos, koalas and the birds of paradise – in his essay “On the Zoological Geography of the Malay Archipelago” (1859) and later in his book “Distribution of animals” (1876).

Fig.3. Faunal regions in Indonesia, as  proposed by Wallace in 1876 (image in public domain).

Wallace couldn’t know of the tectonic forces modifying the islands of Indonesia and he could only cautionary speculate about sea level variations, but he deduced correctly that the observed distribution of animals is explained only by large changes of earth’s surface in the geological past.
During the last ice age the level of the sea was much lower than today, exposing the continental shelf between Asia and Australia. Asia formed with the mountain ranges of Borneo, Sumatra, Java and Bali the lost continent of Sunda, Australia was connected to New Guinea in the lost continent of Sahul.
Between these two continents, colonized by animals coming respectively from Asia and Australia, a narrow strait of sea formed a natural barrier even during the last glacial maximum. In the strait some isolated islands persisted, like Celebes, Timor and Flores, and organisms evolved even more peculiar adaptations to survive there. The former natural barrier was named in 1868 by the naturalist Thomas Henry Huxley “Wallace Line” and the region of isolated islands, never reached by large tetrapods from Asia or Australia, is known today as “Wallacea“.

Fig.4. Topographic map of Sunda, Sahul and Wallacea

But back to England in 1858. Darwin was prompted by Wallace’s letter and manuscript to finish his summary on his theory “On the Origin of Species by means of natural selection, or the preservation of favored races in the struggle for life” (published in November 1859).  It is interesting to note that one of the main mechanisms of his theory, the selection acting on the variations between specimens, was significantly improved in Darwin’s writings between May and June 1858. This prompted some authors to claim that Darwin adopted this fundamental principle of evolution from Wallace’s letter. Apart the question when exactly the  letter from Ternate was delivered to Darwin (early May or late June, there are no exact records in Darwin’s documents), there is no reason to doubt that Darwin had collected enough data since his Voyage on the Beagle to realize and deduce the mechanisms of evolution for himself – nevertheless Wallace’s letter gave him the final push to finally publish his theory.
But reducing Wallace’s contribution to the theory of evolution to a simple bystander would do injustice to this extraordinary naturalist, who was not afraid to speculate even on the habitability of other worlds. Wallace’ experience with the variations in a single population (as salesman he was familiar with hundred of specimens of a single species) made him an important ally to promote this idea in the scientific establishment.

Along with Darwin, Alfred Russel Wallace must be considered one of the pioneers of evolution, a fundamental principle to truly understand the history of earth.

Bibliography:

GLAUBRECHT, M. (2008): Alfred Russel Wallace und der Wettlauf um die Evolutionstheorie Teil 12 . Naturwissenschaftliche Rundschau 61(7): 346-353
GLAUBRECHT, M. (2008): Alfred Russel Wallace und der Wettlauf um die Evolutionstheorie Teil 2 . Naturwissenschaftliche Rundschau 61(8): 403-408

The earthquake killed estimated 40.000 people in the two cities alone, 27.000 people along the shores of the Strait of Messina - some historic documents claim 100.000 to 200.000 victims – one of the deadliest natural disasters recorded during historic times in Europe.

Fig.1. A historical representation – a “Vue de l’Optique composition” (a hand-coloured copper engraving used in a Laterna magica) – shows ships on the Strait of Messina during a series earthquake in 1783 with more than 35.000 victims.

South Italy is located between the borders of the two major continental plates of Europe and Africa and several microplates of the Mediterranean Sea. This geometry forms “belts” with intense tectonic activity, recognized already in 1862.

The origin of the tsunami of Messina is still today an unsolved geological problem. The entire region is dominated by the large rift-zone of the Calabrian Arc, formed by the slow rollback of the oceanic crust of the Ionian Sea.

Fig.2. Simplified tectonic settings of South Italy and the intensity of the December 1908 earthquake after the modified Mercalli scale (data from INGV site). In this model the earthquakes of Calabria and Sicily are mostly associated with a rift valley formed by the rollback of the Ionian Sea.

This tectonic setting is characterized by faults with downwards movements, unusual to produce the upward push needed to generate a tsunami. Also no prominent fault or escarpment was until today discovered in the Strait of Messina or along the coasts of Sicily. Finally it is strange that the tsunami hit the shores 8 to 10 minutes after the quake, too late according to some researchers to be associated directly to the quake. A new hypothesis proposes that the tsunami of 1908 was therefore the result of a large underwater landslide, triggered by the earthquake.

The bottom of the sea revealed also that tsunami are frequent (in geologic time) catastrophes in the Mediterranean Sea. In sediments of the bay of Augusta (Sicily) researches discovered twelve layers, dated to 4.500 years, with microorganisms, especially foraminifers, living along the shores of the island. These layers were probably formed during past tsunami, when sediments were eroded from the beach and then transported by the backwash currents into the bay.

Bibliography:

MARAMAI, A.; GRAZIANI, L. & TINTI, S. (2007): Investigation on tsunami effects in the central Adriatic Sea during the last century – a contribution. Nat. Hazards Earth Syst. Sci. (7): 15-19
PIGNATELLI, C.; SANSÒ, P. & MASTRONUZZI, G. (2009): Evaluation of tsunami flooding using geomorphologic evidence. Marine Geology 260: 6-18
SMEDILA, A.; DE MARTINI, P.M.; PANTOSTI, D.; BELLUCCI, L.; DEL CALO, P.; GASPERINI, L.; PIRROTTA, C.; POLONIA, A. & BOSCHI, E. (2011): Possible tsunami signatures from an integrated study in the Augusta Bay offshore (Eastern Sicily-Italy). Marine Geology 281: 1-13
SOLOVIEV, S.L.; SOLOVIEVA, O.N.; GO, C.N.; KIM, K.S. & SHCHETNIKOV, N.A. (2000): Tsunamis in the Mediterranean Sea 2000 B.C.-2000 A.D. Advances in Natural and Technological Research, Kluwer Academic Publisher: 260

In theory a tsunami can trigger a variety of erosion and depositional processes, like uprush and backwash currents, turbidity currents, debris flows and landslides, therefore also the formed sediments can vary from fine-grained sediments to large boulders.

- When the tsunami hits the coast it will first erode older sediments. The peculiar (and controversial) “molar tooth structure“, described along the unconformity of older sediments to tsunami sediments, is formed when vibrations of the earthquake crush older layers and the tsunami breaks off regular slabs of soil (rip up clasts). Also liquefaction phenomena, like sand dikes, can be preserved in the sediments underlying the tsunami deposits.

Fig.1. Very schematic stratigraphic succession of tsunami – deposits.

- The tsunami inundates the land and transported sediments and debris are deposited. The sediments of the uprush and backwash currents of a tsunami, consisting of thick sand layers, are described by this post at the “Trough The Sandglass” blog. Unfortunately the preservation – potential for such sediments in an unstable environment like a beach is very low, explaining in part why until now tsunami are underrepresented in the geological record. Also many features found in these layers (like grain-size distribution or the accumulation of marine fossils) are very similar to sediments deposited by storms.

- A tsunami can also transport and deposit giant boulders (like reef debris). Such boulders are unlikely to be reworked by normal processes of a coastal environment and have a greater potential to become fossilized. In November 2007 a team of geophysicists from the University of Texas announced the discovery of possibly the largest tsunami transported boulders ever recorded. However also such boulders seem not to be always unequivocal evidence for a tsunami. Large megaclasts found along the cliffs of the Irish Aran-Island, ranging in weight from 20 to 230 tons and regarded as tsunami deposits, were reinterpreted in 2004 as boulders moved by strong storms coming from the Atlantic Ocean.

Fig.2. A boulder transported by a catastrophic tsunami during the eruption of  Krakatoa in 1883 (image in public domain).

There is also indirect biological (apart marine fossils found on land) evidence for a tsunami.

A strong earthquake can cause not only a tsunami but can also lower the coastal area below sea level. The salt water soon will kill trees and plants growing there. The trees of these “Ghost forests” are finally buried in the sediments of the tidal flat. Slowly the land will rise again due the continuing tectonic movements.
These changes can be observed in the stratigraphic succession: layers of peat or soil with fossil trees will change suddenly to layers of sand, deposited by the tsunami and the tides. A great advantage of such a stratigraphic succession is the possibility to date the organic remains with the radiocarbon dating method and produce exact prehistoric chronologies of these changes.

A paper published in 2009 analyzes the use of trimlines, the limits of the area devastated and eroded by the tsunami, to map the extent of a tsunami. The research identified various trimlines in the area affected by the 2004 tsunami, dating back about 300 years.

The shores of continents are today densely populated areas – the study of the geologic effects and sediments of a tsunami can help to improve our records of prehistoric events and better define the risk for such areas.

Bibliography:

ATWATER, B.F.; SATOKO, M.-R.; KENJI, S.; YOSHINOBU, T.; KAZUE, U. YAMAGUCHI, D.K. (2005): The Orphan Tsunami of 1700 Japanese Clues to a Parent Earthquake in North America. U.S.G.S. – University of Washington Press: 144
BOLT, B.A. (1995): Erdbeben – Schlüssel zur Geodynamik. Spektrum Akademischer Verlag, Berlin: 219
DAWSON, A.G. & STEWART, I. (2007): Tsunami deposits in the geological record. Sedimentary Geology 200: 166-183
GOTO, K.; KAWANA, T. & INAMURA, F. (2010): Historical and geological evidence of boulders deposited by tsunamis, southern Ryukyu Islands, Japan. Earth-Science Reviews 102: 77-99
SCHEFFERS, A. & KELLETAT, D. (2003): Sedimentologic and geomorphologic tsunami imprints worldwide-a review. Earth-Science Reviews 63: 83-92
TAPPIN, D.R. (2007): Sedimentary features of tsunami deposits – Their origin, recognition and discrimination: An introduction. Sedimentary Geology 200: 151-154

Large impacts were relatively rare in historic times; the most famous (and still controversial) is the Tunguska event in 1908. However because of the remoteness of the Siberian taiga the destruction and human fatalities were limited.
Interests on this kind of catastrophe arouse late, only in the mid 20th century the possibility that earth can be hit by large chunks of extraterrestrial material became widely accepted, when in 1960 the geologist Eugene Shoemaker settled the debate about the origin of a large crater in Arizona, confirming an older hypothesis that it was not of volcanic origin but formed 50.000 years ago by an impact.

In 1994 the comet Shoemaker-Levy 9 impacted on Jupiter, the event followed by most mass media. Maybe influenced by the great interest of the public, since 1997 various movies on meteorites have been released.
An advantage for a disaster movie to deal with an impact is the supposed catastrophic effects, especially of large objects, which can affect the entire surface of earth. However a disadvantage is the supposedly short duration of the disintegration and explosion of the extraterrestrial body. A movie writer has to put the catastrophic event at the end of the movie and fill the rest with a love story or personal tragedies.

“Asteroid” (1997) is a cheap TV production with many elements found in similar disaster movies. After the discovery of the approaching asteroid some laser-beams are used to destroy it. However some fragments reach earth and still manage to destroy various cities.

In the more expensive “Armageddon” (released in 1998 with a 140 million dollars budget) a crew of stereotypically characters and an atomic bomb are send onto the approaching asteroid with the estimated “size of Texas“. The bomb is planted in just 250m depth on a more than 1.000km large mass – why even bother to drill? Also by detonating the bomb and considering the inertia of the asteroid, simply a rain of minor chunks would bombard earth – causing anyway worldwide devastation.
The introduction of the movie also mentions the Chicxulub-impact (“it happened in the past, it will happen again“), however showing earth with the modern conformation of continents and oceans (according to plate tectonics a geologic impossibility).

Also the “Super Mario Bros.” movie (1993) starts with the premise of the Chicxulub-impact. However here the cosmic rock rips apart the space-time-continuum and produces an alternative earth, still ruled by anthropomorphic descendants of the dinosaurs.

“Deep Impact” (1998 with a 75 million dollars budget) was released 2 months before “Armageddon” and is in some parts more accurate than the later movie. Also in “Deep Impact” atomic bombs are used to prevent the imminent impact of an 11km large comet, but again some fragments arrive to earth, killing millions of people.

“Meteorites!” is another TV-production from 1998 dealing with a shower of meteorites which cause destruction in a small American town. “Tycus” (1998) and “The Apocalypse” (surprisingly released in 1997) are also both cheap productions intended for the video-market and dealing somehow with comets. “Meteor Apocalypse” (2009) was produced and distributed by “The Asylum Films“, a company famous for their movie rip-offs. Here the melting ice from a comet contaminates the groundwater of earth.

A much earlier movie is “Meteor” (1979), with an only 8km in diameter large meteorite that will hit earth in just six days. To build up suspense smaller chunks (it seems that meteorites in movies never space travel alone, however we could assume that gravitational forces split up a larger asteroid/comet, like Shoemaker-Levy 9) hit earth first. Again rockets are used to blast the nearby meteor into pieces, but again chunks fall on earth causing again havoc. The special effects are terrifying cheap, even considering the year of release. This movie mentions also the origin of the idea to use bombs to stop the meteor: “Project Icarus“, developed in 1968, was an assignment by Professor Paul Sandorff for a group of MIT graduate students to design a way to deflect the asteroid “1566 Icarus“.

Appropriately in the movie “When Worlds Collide” (1951), predating “Project Icarus” and where an entire planet is approaching earth, humanity tries to build a space ark to evacuate the doomed world.

“The Day The Sky Exploded” (1958) is an Italian science-fiction story with a slightly modified version of the asteroid-scenario: here a lostspaceship with an atomic engine first explodes inside an swarm of asteroids, changing the orbit of the swarm towards earth.  To prevent the final impact all nations of earth fire contemporary their nuclear weapons to the sky.

It’s interesting to note that movies produced before 1960 (when most research on impacts were done) use mostly planets rather than asteroids as threat for earth.

“Planet on the Prowl” (1966) is another Italian movie, following the tradition of planet-movies, however here it is the gravitational force that unleashes storms, waves and disasters on earth. A team is send into space to destroy the planet, but here they discover that the celestial body is a living (!) cybernetic organism that will not simply surrender without fight…
A very similar plot was already used by director Antonio Margheriti in “Battle of the Worlds” (1961), where the mainframe of an alien spaceship, mimicking a planet, is attacking earth…

Bibliography:

KAY, G. & ROSE, M. (2006): Diaster Movies. A Loud, Long, Explosive, Star-Studded Guide to Avalanches, Earthquakes, Floods, Meteors, Sinking Ships, Twisters, Viruses, Killer Bees, Nuclear Fallout, and Alien Attacks in the Cinema!!!! Chicago Review Press: 402

*This image is the cover of a videotape, DVD, Blu-ray Disc, etc. and the copyright for it is most likely owned by either the publisher of the video or the studio which produced the video in question. It is believed that the use of low-resolution images of video covers qualifies as fair use under United States copyright law.