Few volcanic eruptions are as well known as that of Mount Vesuvius in A.D. 79. After a wave of hot gas and ash, called a pyroclastic flow, engulfed nearby Pompeii and killed those left in the city, more layers of ash from the eruption buried the buildings and bodies. When the town was excavated in the 19th century, archaeologists found human-shaped cavities in the ash where bodies had decomposed. By pouring plaster into these holes and then removing the surrounding ash, the archaeologists were left with exquisitely detailed facsimiles of Pompeians, in some cases showing the type of fabric worn by the victims and even faces contorted eerily in the rictus of death.
These plaster casts have provided researchers and storytellers with an incredible window into the once-important and thriving Roman port city. Some of the plaster molds show two people embracing; another appears to be a parent trying to protect a child; still another shows a pregnant woman. Books, documentaries and a 1935 film have explored the city and its doomed inhabitants.
Now, Pompeii is again getting the Hollywood treatment. Directed by Paul W. S. Anderson (best known for Resident Evil and Alien versus Predator), the new film, Pompeii, cannot be classified as a documentary. Mount Vesuvius is more a backdrop than a centerpiece. Still, Anderson and the film’s promoters maintain that the team went to unusual lengths to accurately portray the history and science of the city as well as the eruption. For example, “we LiDAR-scanned the buildings and the streets,” Anderson says, and then re-created a digital version of the city by overlaying a computer-generated model over helicopter shots of the devastated city.
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Sarah Yeomans, an archaeologist at West Virginia University who has studied Pompeii extensively, says the film correctly portrays the city’s layout. “The amphitheater was in the right place…in relationship to the palaestra,” a large open area for sporting activities, Yeomans says, calling it “a detail only someone like me would notice.” Other details of the city such as graffiti on the walls of buildings and raised stones in the streets that people would walk on when it rained were “very characteristic” of the city, she says.
Other parts of the film are less historically accurate. “Probably one of the biggest modern concessions that Anderson made was the role of the women in the cities,” Yeomans says. In the film the wife of Pompeii’s mayor takes part in business negotiations; Yeomans says that aside from “very exceptional circumstances” upper-class women at that time “were very sheltered” and would not have participated in politics or business deals. But Yeomans acknowledges that Anderson had to balance history with modern sensibilities. “To have a movie like that where you pretty much take women out of the storyline would not resonate with modern audiences,” she says.
The rendition of the volcanic eruption itself also required taking several “artistic licenses,” as Rosaly Lopes, a volcanologist at the NASA Jet Propulsion Laboratory, puts it. For one, the large chunks of flaming, semimolten rocks that crash down onto the city normally would not occur in this type of eruption, Lopes says. So-called Plinian eruptions—named for Roman statesman Pliny the Younger, whose written observations of this very eruption have helped scientists piece together the story of Pompeii and Vesuvius—would instead send large and small chunks of solid, nonflaming pumice flying through the air. “Those incandescent lava bombs didn’t happen with that kind of eruption,” Lopes says. Whereas there were likely widespread fires as shown in the film, they would have been caused by toppled oil lamps rather than flaming projectiles.
Lopes took issue with two other parts of the film’s depiction of the eruption. At one point, before the eruption begins, there’s a shot of the interior of the volcano’s crater showing a magma lake. Lopes says that magma wouldn’t have been visible before the explosion; in Plinian eruptions pressure builds up beneath a hardened surface before finally exploding.
The film also shows a large tidal wave, caused by the powerful eruption, which sends at least one ship from the nearby bay crashing into the city itself. Lopes says that although there was a small wave described by Pliny, it would not have been nearly large enough to carry a ship into the city. “There was certainly no boat found in the city,” she says.
And whereas the sequence of events around the eruption in the film was accurate, Lopes says, the time frame was somewhat accelerated. The first explosion did indeed occur around 1 P.M. local time but it wasn’t until the next morning that the pyroclastic flows first reached the city. Anderson also acknowledges this concession to the art of storytelling. “Despite the reality of it, you don’t want the characters sitting around for a couple of hours,” he says.
The pyroclastic flows themselves, which is what actually killed most of the victims, were well done, Lopes says. Victims died from heat shock; in the case of Pompeii the temperatures may have reached as high as 300 degrees Celsius, according to a 2010 study. And the flows can travel at incredibly high speeds down the sides of a volcano; an estimate of the average speed of the pyroclastic flow down the slopes of Mount Saint Helens in Washington State during its 1980 eruption (also Plinian) was around 230 kilometers per hour. The depiction of a column of gases and ash rising from the volcano that darkened the skies and generated lightning was also accurate, Lopes says.
Pompeii opens this Friday. Check it out if you want to see a CGI sword-and-sandal disaster flick, but perhaps skip it if you bemoan any scientific inaccuracies whatsoever in modern cinema.