Pompeii Volcanic Eruption – August 25, 79

Eruption of Mount Vesuvius destroyed Pompeii and killed its residents – On the Bay of Naples in Southern Italy

In the early morning of August 25, 79, a mass of pyroclastic material erupted from Mount Vesuvius and, traveling at more than 60 mph, collapsed over the town of Pompeii. Hot ash, lava fragments, and poisonous gases were blasted into homes through tiny openings in windows, doors and roofs. Everyone in the town was killed, but not instantaneously. As people inhaled the hot gases their lungs quickly filled with fluid. It was just like swallowing fire. With subsequent breathing the victims found themselves gradually suffocating in a painful death as their windpipes became clogged and their lungs stopped working. It was all over in a short time and, before the end of the day, Pompeii had been covered and destroyed by a twenty-foot blanket of volcanic debris. For more than 1,500 years the town lay buried and forgotten. All that remained was the memory until, after a long time, it was discovered by accident.

Mount Vesuvius is one of a chain of volcanoes stretching northward along the length of Italy. These volcanoes lie at the junction of the African Tectonic Plate and the Eurasian one, a location where there is always a zone of either pressure or tension. For millions of years the African Plate has been pushing against the Eurasian one along a line of action that stretches from Gibraltar to Turkey. From time to time, in the short term, a weak area gives way and either an earthquake or a volcanic eruption is the result. Over a much longer period, the influence of the African Plate gave rise to the Alps. The peak of Mount Vesuvius is about four thousand feet above sea level and six miles from Pompeii.

The accidental discovery of Pompeii’s ruins happened in the sixteenth century when an underground irrigation canal was being dug and the workers found themselves cutting through old buildings. An inscription “Pompeii” was found on one wall and people thought it was the name of a house belonging to a wealthy person. Nothing was done about this discovery and two more centuries elapsed before further attention was paid to the buried buildings and even then the focus of interest lay in a search for any valuable objects that might be there. Many people visited the ruins in the eighteenth century but it was only after Italy became a united nation in 1860 that serious study was devoted to it. King Emmanuel II commissioned Giuseppe Fiorelli, a well-known archeologist, to conduct a thorough excavation of the ancient city of Pompeii. He worked on the project with great precision, creating a series of zones in which each one represented a number of houses. He arranged an identifying number for each building.

Fiorelli kept a meticulous record and also made sure that buildings would remain intact by excavating from the roof down. His plan was to leave as much as possible of the site in its original form and location. He did something else that was his own idea. It turned out to be the unique contribution that enables us today to see in three dimensions exactly what happened within individual homes as the volcanic ash arrived. In 1863 he noticed as debris was being cleared away that cavities resembling bodies began to appear in the volcanic material, so he found a kind of plaster that he could force into these cavities under pressure to prevent them collapsing. The result was extraordinary. The volcanic ash had solidified around human and animal bodies to such a degree that the smallest detail could be identified. The addition of the plaster meant that Fiorelli now had complete three-dimensional models of people and animals exactly as they had been in their last moments of life. Victims frequently died in agony as the ash smothered them and the pain of their experiences was clearly etched in their faces.

No one in living memory ever expected to see Mount Vesuvius erupt. It had been quiescent for many centuries and generation after generation had worked the land up the slopes of the mountain. Volcanic ash from time past had provided an ideal foundation for good soil so all kinds of crops were grown, often as many as two crops from a single field in a year. Wine, wheat, and a variety of sauces were shipped regularly to France, Greece, and Egypt. The warm Mediterranean climate, proximity to the ocean, and the advantage of being part of the Roman Empire all gave Pompeii a huge advantage for trade. It is not clear how many people lived in the town at the time of the eruption because Pompeii had been hit with an earthquake, a common occurrence in that area, seventeen years earlier and it had destroyed much of the town. At that time the population was more than ten thousand. Every effort was made to restore the town in the wake of the earthquake because it was such an agricultural paradise and every person benefited from its success. We may not know the exact population in 79 but we do know that thousands died instantly when the eruption occurred.

Fortunately for us today there were many historians in Italy and we have first-hand accounts from some of them. Pliny the Elder was a much respected historian and he happened to be near Pompeii at the time of the eruption of Mount Vesuvius. He was fifty-six years of age, old for that time, a bit overweight, and suffering from asthma, so Emperor Titus decided to give him an easy responsibility, looking after the Roman fleet at Misenum, twenty miles northwest of Pompeii in the Bay of Naples. It seemed like a very comfortable position for him but he arrived at the wrong time for any ease, in the early part of August of 79. On the morning of the twenty-fourth of that month a servant came to him to report the appearance of a strange cloud hovering over the Bay of Naples. Pliny’s description of the cloud and his experiences throughout the remainder of that day were recorded carefully by those who were with him, especially by his nephew, later known as Pliny the Younger. They provide a vivid picture of the impact of the eruption on individuals. In the case of Pliny senior, despite all the efforts by him and his staff to safeguard their lives, the twenty-fifth of August proved to be Pliny’s, as well as Pompeii’s, last day.

Pliny the Elder described the cloud as an immense tree trunk rising high into the air and opening out into many branches. He realized at once that he was witnessing a major natural event so he ordered his staff to make ready a small galley to take him closer to the cloud. Just as he was about to leave he received an urgent call for help from some friends who lived on the slopes of Mount Vesuvius. He immediately ordered several additional boats to go with him toward Pompeii to help in the rescue. As the boats approached the nearest beach to Pompeii, Pliny noticed that ashes were falling in increasing density, getting thicker and hotter and accompanied with black pumice stones and cinders, as they got closer. Suddenly, as they reached shallow waters, they found they could not go further as the waters had become blocked with debris from the mountain. They changed course southward and landed at Stabbiae, about five miles to the south of Pompeii. Panic had overtaken the crew of the ships as night approached and the night sky continued to be lit up with flashes of fire. Pliny made every effort to calm things down. He took a bath and a leisurely dinner and encouraged everyone to have a good night’s sleep. The morning of the twenty-fifth of August seemed to come suddenly as they awoke to loud noises with the walls of their house violently swaying backwards and forwards. The ships in the harbor were being tossed about like toys. Although daylight had come it was still pitch-dark and as Pliny stepped outside the house he was met with sulfur fumes and a hail of pumice particles and ash. He collapsed, unable to breathe, and died.

The beginning of the eruption of Mount Vesuvius began on the afternoon of the previous day, the twenty-fourth of August, in the form of the cloud of ash and smoke that Pliny had observed from Misenum. Molten ash and pumice was being ejected from the volcano at a rate equivalent to 600 mph. Ten thousand tons of it left Mount Vesuvius every second. Much of the pumice consisted of pieces larger than a baseball. Within minutes, of the start of the eruption, the cloud of debris had risen nine miles into the sky, a height well beyond that of Mount Everest. Normally, in August, the wind direction over the Bay of Naples is from the northeast. On this occasion, however, it came from the northwest so the fallout was carried over Pompeii. The sky was dark and all over Pompeii people were lighting lamps in the middle of what would normally be bright daylight. Layers of pumice and ash were accumulating on roofs and buildings were shaking constantly from the earth tremors. From time to time a large piece of volcanic rock would crash through the roof of a building. By late afternoon the column of material from the mountain had risen to a height of ten miles, a hundred million tons of ash and pumice had been ejected and Pompeii’s streets were twenty inches deep in volcanic debris.

Early in the morning of August twenty-fifth a series of pyroclastic surges emerged from Mount Vesuvius. The volcano’s mouth had collapsed and volcanic material was being ejected at fifteen times the earlier rate. This column of ash and pumice was now so dense that it began to collapse and flow down the mountain slope as a glowing red cloud. Its temperature exceeded 1,500 degrees Fahrenheit and, as it rushed toward Pompeii at sixty miles an hour, the town was smothered. Pliny the Younger, the nephew of the Pliny who died at Sabbiae on the twenty-fifth of August, was still at Misenum when the final destruction of Pompeii occurred. He took time to write an account of it all and he sent it to the historian Tacitus a few years later. His descriptions are the best records we have of Pompeii’s final day. So widespread was the destructive power of these final pyroclastic surges from Mount Vesuvius that places like Misenum, twenty miles away from the mountain, were so badly shaken and so heavily covered with volcanic material that people felt they had to get as far away as they could. Pliny persuaded his mother to follow him out of Misenum and together they managed to get to a place that was beyond the reach of the falling debris.

From his vantage point north of Misenum, Pliny saw the entire area between him and Pompeii covered with one black cloud. The sea was like the land and we know now that pumice fragments, the main part of the material that flowed from Vesuvius, is lighter than water so it formed a new surface on the ocean. He felt like a person who had been locked in a sealed room without light because in every direction he saw darkness all through the next day. All around him the cries of people and children went on throughout that day. Occasionally there was a flash of light, not from the sun but from the fire that accompanied the cloud and fortunately never reached Pliny’s location. All around him ashes were falling steadily and to avoid being buried and crushed beneath them he had to get up periodically and shake them off. Finally, Pliny saw some glimmers of light and then he saw the sun. It was very faint, as if an eclipse was occurring. He and his mother began the journey back to Misenum. Everything and every place were different because of the thick layer of ashes that looked like a giant snowfall.

Mount Vesuvius has erupted dozens of times since that fateful day in 79, including ten times between 200 and 1100. Then, for five hundred years from 1100 to 1600, just as it had been in the period before 79, it was quiescent. No doubt people were lulled into a false sense of security in those times too because their knowledge of geological activities was as inadequate as it was in Roman times. In 1631 Vesuvius burst into action once again and continued frequently until its final eruption in 1944. It seems to an onlooker now that the crater is sealed shut with not even a sign of smoke emerging from it. The one thing we do know, and this was not known even as recently as 1944, is that the underground motions of the great tectonic plates that cover the earth are constantly in motion and always will be. In particular, the two plates that meet in Italy are today pressing against each other, building up pressures that someday will give rise to new earthquakes and fresh volcanic eruptions.