How long did it take for the eruption of the mighty Vesuvius to destroy Pompeii? Pompeii is an ancient Roman city located near modern-day Naples, Italy.The city was completely buried by volcanic ash and pumice in 79AD after Mount Vesuvius erupted. The invisible force of this catastrophic event could be hoped to be understood by analyzing different aspects, such as the timing of the eruption, the speed of the mounds it ejected and the spread of the ashes.
According to The Guardian, the earliest archaeologists to unearth the ruins of Pompeii determined that the eruption was relatively sudden, and yet evidence suggests it must have been virtually instantaneous. While the exact time of the event is unknown, scientists can estimate that the whole process interrupted over the course of approximately 10-14 hours and with complete destruction being made in about 20-30 minutes.
The speed of the eruption, in particular the amount of time it took to the entirety of the city to disappear under the ash, is thought to be around 500-600 mph. This is because within only 4 hours, the settlement was engulfed in over 4 meters of ash and pumice, a type of rock composed of solidified lava. In a further 8-10 hours, the city was covered by over 9 meters of ash.
Furthermore, it has been hypothesized that the ash and pumice stones may have travelled around 6 to 9 miles in this time, according to experts. This would explain why the nearby cities such as Herculaneum and Stabiae were also fallen victims to the eruption.
The scale of the disaster may be hard to grasp, but some evidence suggests that it may have affected the surrounding area in more subtle ways. For instance, St. Mary of Egypt Monastery, a couple hundred miles away from Pompeii, is thought to have its walls coated with a fine layer of ash from the eruption of Vesuvius.
Heat Distribution
What also sets this eruption apart from its predecessors is the incredibly high temperatures it generated. Research indicates that the thermal effects of the explosion were so intense that they essentially “turned the walls of the houses into a grainy paste”. The fact that some of the victims of the explosion were found carbonized in this paste makes it likely that temperatures of up to 500 degrees centigrade were reached.
This intense heat is thought to have been dispersed over the wider region wherever it came into contact with walls, people or materials. However, it is believed that the blast may have originated from somewhere between 5 and 9 kilometres away, meaning within this range the full force of the heat may have been felt. To add to its immense power, Vesuvius would have also discharged energy waves like sonic booms that are known to travel outward along the ground for up to 30 km.
The seismic vibrations of the eruption must have been earth-shattering. Some scientists believe that the occurrence would have forced thousands of houses to collapse, reinforced walls to crumble and caused catastrophic flooding along the river course called Tiber which passes through the city. It is also thought that the eruption saw over 12 million tons of ash released in the first two hours.
Volcanic Plume
The volcanic plume is another major factor which contributes to the understanding of the speed of the eruption. Although estimates vary, on the first night of the eruption it is thought that the plume could have spanned up to 30 kilometres high and spread over an area around 100km in circumference. This would explain why the resulting ashes and pumice stones lay spread across a large area; encompassing present day Pompeii, Herculaneum and Oplontis.
Moreover, the plume would have changed shape and size throughout the eruption. Accounts from Pliny the Younger describe how during its climax the explosion morphed into the shape of a pine tree; this is consistent with other modern day eruptions and the scientific notion of an ash-enriched eruption column. In other words, during the final stage of the explosion, the mostly pumice stone and ash-filled plume from Vesuvius rose higher into the atmosphere carrying the particles of ash and pumice even further than it had before.
Interestingly, the ashes from this eruption are so specific that it has allowed researchers to verify the exact source of the eruption with astonishing accuracy. Scientists have conducted tests on material unearthed in and around the ruins of Pompeii and due to the remarkably uniform composition of the ash, it has indicated that the majority of the ashes have come from the same source and at the same time.
Airborne Particles
It is also believed that some of the particles erupted from Vesuvius eventually dispersed into the atmosphere and travelled even further than the region it occupied. Evidence of this exists in the fact that some of the surface soils near the summit of Vesuvius have been found to contain particles that are likely to have come from the Roman period eruption.
Furthermore, a network of scientific laboratories located in various parts of the world recently collaborated to investigate materials taken from numerous archaeological sites and concluded that the evidence of certain elements deemed to be associated with the eruption of Vesuvius was there. Further chemical analysis of these elements added further credibility to the notion that the particles travelled through the atmosphere and settled into other regions of the world.
Effects on the Weather
It is theorized that the eruption of Vesuvius had an extreme impact on the weather. Scientists believe that during the period of the eruption, hot hurricane-like winds may have spiralled down from the plume and caused extreme temperatures, lightning and thunder over the affected area. Unbelievably, reports from the Mediterranean suggests that ashes from Vesuvius even reached the modern day Cyprus, 460 miles away from Pompeii.
Other evidence suggests that the dust and particulate matter from the eruption had a direct effect on the environment and the climate. For instance, analysis of ice core samples revealed that during the winter of 79AD, the amount of sulphate and other particles were abnormally high. This would mean that the temperatures during winter and spring of 79AD would have been much cooler than usual.
Consequently, the effects of the eruption of Vesuvius would have been felt not only by those living in the Campania region in 79AD but also beyond.
Generated Pressures
The pressures of the eruption are likely to have been much greater than the average volcanic eruption. Analysis of the ash layer in and around Pompeii suggest that a combination of forces was at work here. This was reflected in the magnitude 8.1 eruptions and the shocks associated with it. Furthermore, near the epicentre of the blast, an estimated 159 psi energy would have been generated. In other words, about 16 times more than a level 5 tornado.
The pressure would have caused devastating physical destruction to the buildings, lampposts and human remains that are found in and around Pompeii and Herculaneum. This is evidenced by the fact that some of the human remains were covered with up to 40cm of ash deposits and even remains of the buildings were found in a highly fractured state.
This indicates that the eruption must have had a staggering force, which would have been inflicted not just on the beings but also on the buildings and other man-made structures.
Debris Field
By assessing the debris field left in the wake of the eruption, scientists have been able to deduce the velocities of the pyroclastic flows from the main explosions. It is believed that the flows initially moved at a velocity of between 60 and 66 metres per second. As the explosion progressed, the force of the eruption was further accelerated and the flow eventually reached speeds faster than 74 mph.
It was therefore estimated that a sustained pyroclastic flow was able to cover a distance up to 9.2 kilometres away from the center of the eruption in just an hour. It is also believed that the explosions to have travelled up to an 11.2km radius within a couple of hours of the initial eruption.
Apart from this, numerical simulations conducted by scientists have indicated that a dome of ash and pumice containing numerous volcanic rocks up to a diameter of 2.5m may also have been formed over Pompeii. This comparison is particularly useful for historians because the debris materials that were formed in the process are thought to be similar to those deposits seen in modern day volcanic eruptions.
Soil Erosion
The ash from the eruption is thought to have begun to settle in the soil as it flew away from Vesuvius. This type of soil erosion process is known as ballistics and is when particles of sensible dust, ash and pumice were thrown from the eruption into the region. As these particles settled onto the landscape, it is thought it would have affected crops, animals and other vegetation.
It is also theorized that the dust and ash cloud generated by the eruption would have been so colossal that it would have blocked out the sun and night sky. This would have posed a severe threat to all living organisms as it hindered their ability to carry out vital tasks such as hunting, fishing, gathering food and thus putting their lives and livelihoods in peril.
As a result, the hazardous mix of dust, rain and ash in the air is believed to have caused a drastic decrease in food production and thus, deteriorating the lives of people in and around the affected sites.
Societal Impact
The eruption of Vesuvius was undoubtedly a devastating event, killing over 10,000 people and leaving thousands more homeless. This catastrophic event did not just affect the Campania region but it had far reaching implications that would eventually topple the Roman Empire.
Floods, famine, destruction and diseases caused by this eruption plagued the survivors of the disaster and the saga continues, even today, in the form of the creation of the world’s most famous archaeological site. The destruction, death and chaos left behind by Vesuvius are also testimony to the devastation that can be caused by a single natural event.
The consequences of the eruption, both on the region and its people, were far reaching. This makes it even more astonishing that the city of Pompeii was left untouched for so many centuries before it was discovered in the 18th Century.
