Thursday, 24 March 2016

Herculaneum and Pompeii: pyroclastic surges

An image of Pompeii with Vesuvius in the background.
On the 24th August AD 79, two towns in the bay of Naples were buried and forgotten. Herculaneum and Pompeii both reside in Italy on the bay of Naples, near the volcano Vesuvius. These two towns were preserved to the extent that we can still see and examine loafs of charred bread, people, animals and their possessions. In 2011, I visited both towns and had a glimpse into the past, seeing whole buildings which had survived underneath the ground. The towns have provided a wealth of information on life in Roman towns. This week I am writing about the pyroclastic surges that destroyed both towns.

When Vesuvius, the volcano in Naples, erupted in AD79. Pliny the younger was able to document the devastating events that unfolded. From the earthquakes to the hot ash that fell from the ground to the blackened out sky, all the details were recorded. However, one detail that was disputed for many years was the description of the four pyroclastic surges that hit the towns of Herculaneum and Pompeii. It was in 2010 that a study was conducted and proved that the residents were killed by extreme temperatures instead of the hot ash (Valsecchi, 2010). It was until the modern world observed a pyroclastic surge with its own eyes, that Pliny’s account of the events in AD 79 were revised. The Unzen Volcano in Japan had the same pyroclastic surges as that of Vesuvius.

Pliny the younger’s description of the column of pumice and ash above Vesuvius:
About one in the afternoon… a cloud was ascending, the appearance which I cannot give you a more exact description of than by likening it to that of a pine tree, for it shot up to a great height in the form of a very tall trunk, which spread itself out at the top into a sort of branches; occasioned, I imagine, either by a sudden gust of air that impelled it, the force of which decreased as it advanced upwards, or the cloud itself being pressed back again by its own weight, expanded in the manner I have mentioned; it appeared sometimes bright and sometimes dark and spotted, according as it was either more or less impregnated with earth and cinders” (The British Museum, 2013).

A cast of a person from Pompeii with surviving amphora. 
Once the weight of the column couldn’t be supported anymore the column collapsed on itself, causing the pyroclastic surges. There were six pyroclastic surges and it was the first surge that killed the residents of Herculaneum. The temperature, rising to 300°C of the cloud killed everything it touched, allowing for the town and majority of things in it to be preserved (Valsecchi, 2010). The fourth surge that came from the volcano was the one that hit Pompeii. The speed of these surges meant that people were preserved in their last moments, huddled covering their faces. When visiting Pompeii, you can see the casts created of the people of Pompeii. The casts are beyond shocking, when you look at them you begin to imagine the fear these people experienced during their last moments. This makes them appear as genuine people instead of just figures of the past. Despite this, the information received from the two towns allowed for historians and archaeologists to begin to understand life in the past. Both towns have a wide variety of information to offer the inquisitive minds of the 21st century.  

To see a pyroclastic surge in action, watch the YouTube video of the surges from the volcano Unzen to see their speed and begin to understand the sheer devastation that they can cause.

1.     BBC (2011) History - Pompeii: Portents of disaster. Available at: (Accessed: 22 March 2016).
2.     Eruption timeline (2013) Available at: (Accessed: 22 March 2016).
3.     Geography Video 4 the UC (2010) Dome collapse and pyroclastic flow at Unzen volcano. Available at: (Accessed: 22 March 2016).
4.     Madej, H. and Cristina, M. (2010) Pompeiians flash-heated to Death ‘no time to suffocate’. Available at: (Accessed: 22 March 2016).
Pictures from:
1.     Madej, H. and Cristina, M. (2010) Pompeiians flash-heated to Death ‘no time to suffocate’. Available at: (Accessed: 22 March 2016).
2.     Hay, S. (2013) Available at: (Accessed: 22 March 2016).

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