Happy Anniversary, Mount Vesuvius!

That’s right! On August 24, 79 AD (or CE if you’re gonna be pedantic), Mount Vesuvius erupted outside Pompeii and Herculaneum in the Roman Empire. Or maybe it didn’t. Well, it definitely erupted, but it turns out no one really knows exactly when. Let’s discuss.

When the Hell Are We?

I won’t get into the nuances of figuring out what exactly time is, but suffice to say that time was very difficult to keep track of until very recently. Long ago, the various peoples of the world didn’t have standardized calendars, clocks, or other timekeeping devices. This means that records kept by early civilization must be painstakingly cross-referenced by historians to determine when things happened relative to each other and relative to today.

I’ll provide one quick example of just how pervasive and difficult this is: Until the early 1700s, colonial America used the Julian calendar (named after Julius Caesar). The Julian calendar was similar to the calendar we currently use (called the Gregorian calendar after Pope Gregory XIII), but it was juuuuuust different enough to cause problems. For instance, because the length of the year in a Julian calendar didn’t exactly match up with the true solar year (that is, the amount of time it takes for the earth to make a full trip around the sun), the days started to drift. That meant it was more difficult to plan for farming because eventually the traditional planting or harvesting seasons would be too hot or too cold to actually plat or harvest. So Pope Gregory XIII fixed the mathematical problem and now we use the Gregorian calendar and the slight drifting of time away from the actual solar year is compensated for by leap years.

The other problem with time is that no one really recorded anything about the Vesuvius eruption at the time of the eruption. The best evidence we have is a letter from a Roman named Pliny the Younger to Tacitus, a Roman historian. Pliny the Younger witnessed the eruption first hand, but he didn’t write the letter until 25 or more years after the eruption. Plus, the letter was copied many times between Pliny’s life and the invention of the printing press, so there is a good chance the date in his letter was corrupted in some way. And then there’s the weird way that Romans kept time (that is an article for another day), which makes things even more complicated. Manuscript experts believe the date in Pliny the Younger’s original letter was August 24. Or maybe October 30. Or possibly November 1. Perhaps even November 23.

The point is no one knows. Meteorologists, archaeologists, geologists, and other historians have done studies based on wind direction, sea changes, ash accumulation, and other sciencey things, but still the exact date eludes us. To just make things more confusing, in October 2018 an Italian archaeologist found an inscription written in charcoal dated October 17, 79 AD. If that inscription is contemporary with the eruption, then October 17, 79 AD is the earliest possible date on which Mount Vesuvius could have erupted.

The Eruption

Okay, so now we know that we don’t actually know when Mount Vesuvius erupted. But we do know that it erupted, and we know it was devastating. One of the primary reasons it was so devastating is that the Romans had no idea Vesuvius was a volcano. Can you imagine? Think about some great bit of nature you love, maybe an ocean, or Yellowstone National Park, or a lake, or whatever. Now imagine that one day that beach you love just exploded and killed several thousand people. That would be pretty unnerving, right?

For four days leading up to the eruption, small earthquakes shook the area surrounding the volcano. However, the citizens in the area thought nothing of this and generally stayed where they were. Keep in mind that historians believe there were at least 12,000 people living in Pompeii alone, and Pompeii was just one of several towns that were devastated by the eruption.

Sometime in the early afternoon, the volcano erupted. Ash, debris, and pumice as large as one inch in length rained down for hours. Roofs in the area were bombarded with falling ash, and scientists believe that roof tiles reached temperatures of about 140°F, and these few hellish hours were the final opportunity to escape certain death. Later on the first day of the eruption, another blast occurred that sent piping hot bits of rock, some as large as 4 inches, raining down on the surrounding area. This second column fell for eighteen hours, and scientists believe the ash was hot enough to kill inhabitants. Here is a cool animation showing what the eruption likely looked like in Pompeii:

On the morning of the second day of eruption, the large grey column of gas, ash, pumice, and other volcanic debris collapsed, sending fragments between 350°–700°F all over Pompeii and Herculaneum, both of which were destroyed. Even the best insulated rooms in the best homes in the area reached temperatures in excess of the boiling point of water. The towns around the volcano simply ceased to exist. It is believed that over 16,000 died in the hours immediately after the eruption. Some were killed instantly by falling debris or extremely hot gases. Others suffered.

The Aftermath

Interestingly, the cities of Pompeii and Herculaneum were, at least to the Romans, gone. Scientists believe that Pompeii was buried in 19 feet of ash, pumice, and other volcanic deposits. Herculaneum, in contrast, was buried by 75 feet! Death and destruction were everywhere, and in fact we’re still not 100% sure we’ve discovered it all. The eruption was so large that archaeologists aren’t sure where else to look, really, but most seem to agree that there is likely more chaos to be discovered.

What did the people of Pompeii look like?

In fact, many early historians simply forget about Pompeii. Recordkeeping was lacking, and additional eruptions in the fifth and sixth centuries further covered Pompeii, which was “discovered” in 1592, over 1,000 years after the last eruption and 1,500 years after the initial eruption. Since then, Pompeii and the surrounding areas have become an archaeologist’s dream, and thousands upon thousands of research missions have sought to discover exactly what happened when Vesuvius erupts in 79 AD.

Over a thousand bodies have been found and casts have been made. Additionally, frescoes, villas, and other infrastructure has been uncovered and provided historians with a clearer picture of what life in Roman Pompeii was like. Brothels, restaurants, boathouses, and a forum are just some of the architectural elements that have been discovered. Husbands, wives, fathers, mothers, free men, slaves, and even children have been discovered among the rubble. And this is not an old discovery; less than one year ago, in November 2020, archaeologists uncovered the bodies of who they believe to be a master and slave.

Today tourists can visit Pompeii and the surrounding towns, and can even climb right up to the volcano crater itself. We’ve come a long way as a society in the past 1,942 years, and we know much more about volcanoes and how to prepare for them. However, the field is still somewhat immature, and the bottom line is that sometimes a volcano might erupt with very little or no real warning. Just look at some Mount St. Helens footage from it’s enormous eruption in 1980.

Scary stuff, right? Anyway, happy anniversary, Mount Vesuvius, even though it seems unlikely that today is the actual anniversary.

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