This past Saturday, August 24th, marked the generally accepted anniversary of the 79 CE eruption of Mount Vesuvius in Italy. It has been centuries since the famous volcano erupted and destroyed the cities of Pompeii and Herculaneum, burying them under a pyroclastic flow and preserving them in stunning and tragic detail. An estimated 16,000 people lost their lives in the days that followed. Today, 2,000 years later, scientists are using data gained from such ancient eruptions to ensure that fewer lives are lost when volcanoes erupt.
POMPEII AND HERCULANEUM DESTROYED
When Mount Vesuvius erupted on that fateful day, both Pompeii and Herculaneum were already in the midst of recovering from another natural disaster, an earthquake that damaged the two cities in 62 CE. After this major quake, minor quakes shook the area for years and became a common occurrence for its citizens. So when seismic activity began again in early August of 79 CE, few people took notice. Their complacency proved fatal when Mount Vesuvius literally blew its top, spewing toxic vapors and molten debris more than 20 miles in the air and releasing more than 100,000 times the thermal energy of the atomic bomb that pulverized Hiroshima.
Once the volcano exploded it was too late for most people to escape. Ash blocked the sun and covered rooftops, but it was only a taste of the events to come. Over the next several hours the volcano unleashed its horrible power as pyroclastic surges rained down on the cities, destroying everything and everyone. Herculaneum was buried in volcanic mud which obliterated the city, but Pompeii was covered in volcanic ash so quickly that the city was perfectly preserved along with its victims in that fateful moment in time. 
Much of what we know about the eruption comes from Pliny the Younger who observed it from the city of Misenum across the bay from the mountain and whose uncle, Pliny the Elder, died while attempting to rescue a friend. His account, combined with the incredible amount of information contemporary scientists have been able to gather in the area, provide a detailed picture of the catastrophe that will help to predict and prepare for the next eruption of Mount Vesuvius.
PREDICTING AND PREPARING FOR THE FUTURE
The 79 CE eruption of Mount Vesuvius isn’t the only volcanic event from which scientists are culling information. Much like their counterparts in paleoclimatology and paleometeorology who are using ancient storms to predict the next big hurricane, volcanologists are looking to the past for information on the next big eruption. They agree that the key to making long-term predictions of volcanic behavior lies in knowing its seismic and eruptive history. According to Stephen A. Nelson of Tulane University,
“The best way to determine the future behavior of a volcano is by studying its past behavior as revealed in the deposits produced by ancient eruptions. Because volcanoes have such long lifetimes relative to human recorded history, geologic studies are absolutely essential.”
The more volcanologists know about the history of a specific volcano the easier it is for them to anticipate its future behavior. In his article “Can We Predict Eruptions?,” Peter Tyson likens it to knowing a career criminal’s record and using it to predict his/her next move. When they feel as if they know a volcano and its history, scientists can feel more confident using modern techniques such as monitoring seismicity to make short-term predictions.
Volcanologists also use data from ancient eruptions to create hazards maps. Nelson describes how they study the “sequences of layered deposits and lava flows” from ancient eruptions and use radiometric age dating to determine the frequency of volcanic events. They combine that information with an understanding of the present-day conditions around the volcano in order to design the volcanic hazards maps. These maps are not meant to make short-term predictions of eruptions, but rather they are tools to assist in evacuation, rescue and recovery should an eruption occur or if a short-term prediction suggests an impending eruption. The maps “delineate zones of danger expected from… lava flows, pyroclastic flows, tephra falls, mudflows, floods, etc.”
Vesuvius was a catastrophic event that destroyed thousands of lives and continues to resonate with us today. However, its legacy and that of other ancient eruptions allow us to save lives when modern eruptions threaten.
To learn more about the ancient eruption of Mount Vesuvius and its modern neighbor Stromboli and to see a time lapse video of the modern day famous eruption of Mount St. Helens, click on the videos below:
*To see how meteorologists are using ancient storms to predict the next big hurricane, check out our blog post “Hurricane Season 2013 BCE: Ancient Storms, Modern Predictions.“
2. Nelson, Prof. Stephen A., Volcanic Hazards and Predictions of Volcanic Eruptions, July 3, 2012. http://www.tulane.edu/~sanelson/Natural_Disasters/volhaz%26pred.htm
3. Tyson, Peter. “Can we predict eruptions?”, NOVA Online. http://www.pbs.org/wgbh/nova/vesuvius/predict.html