This Day in History (24-Aug-79) – Mount Vesuvius erupts devastating the prosperous Roman cities of Pompeii

The ancient cities of Pompeii and Herculaneum thrived near the base of Mount Vesuvius at the Bay of Naples. Herculaneum was a city of 5,000 and a favorite summer destination for rich Romans. At noon on August 24, 79 A.D., this pleasure and prosperity came to an end when the peak of Mount Vesuvius exploded, propelling a 10-mile mushroom cloud of ash and pumice into the stratosphere. For the next 12 hours, volcanic ash and a hail of pumice stones up to 3 inches in diameter showered Pompeii, forcing the city’s occupants to flee in terror. Some 2,000 people stayed in Pompeii, holed up in cellars or stone structures, hoping to wait out the eruption. A westerly wind protected Herculaneum from the initial stage of the eruption, but then a giant cloud of hot ash and gas surged down the western flank of Vesuvius, engulfing the city and burning or asphyxiating all who remained. This lethal cloud was followed by a flood of volcanic mud and rock, burying the city. The people who remained in Pompeii were killed on the morning of August 25 when a cloud of toxic gas poured into the city, suffocating all that remained. A flow of rock and ash followed, collapsing roofs and walls and burying the dead.

In 1748, a farmer found traces of Pompeii beneath his vineyard. Since then, excavations have gone on nearly without interruption until the present. In 1927, the Italian government resumed the excavation of Herculaneum, retrieving numerous art treasures, including bronze and marble statues and paintings.The remains of 2,000 men, women, and children were found at Pompeii. After perishing from asphyxiation, their bodies were covered with ash that hardened and preserved the outline of their bodies. Later, their bodies decomposed to skeletal remains, leaving a kind of plaster mold behind. The rest of the city is likewise frozen in time, and ordinary objects that tell the story of everyday life in Pompeii are as valuable to archaeologists as the great unearthed statues and frescoes. The last major eruption happened in 1944, since then there have been hundreds of minor earthquakes in the region around Mount Vesuvius.



This Day in History (10-Apr-1815) – Mount Tambora in Indonesia Begins Erupting

Six hundred miles east of Jakarta, the capital of Indonesia, Mount Tambora stretches nearly 9,000 feet above the Java Sea on the island of Sumbawa. The volcano originally grew to about 12,000 feet elevation before a major explosion destroyed its summit and left a pre-1815 caldera more than 43,000 years ago. On April 10, 1815 evening, the towering peak exploded violently, killing more than 100,000 people, directly and indirectly, as it spewed rock and ash high into the atmosphere. The eruption, lasting more than three months, is the largest in past 10,000 years and, arguably, the most influential on a global scale.

The eruption emptied about 50-150 cubic km of magma and measures 7 on the VEI scale. It produced a giant plinian eruption column, which is estimated to have reached more 40-50 km altitude, ejecting large amounts of ash and aerosols into the stratosphere. With the cataclysmic eruption, the entire shape of the mountain changed. The caldera — the central peak — collapsed into the magma chamber below, decreasing the height of Mount Tambora by more than 5,000 feet as ash and rock shot up from below. Caldera collapse destroyed 30 km3 of the mountain and formed a 6 km wide and 1250 m deep caldera. Floating islands of pumice 3 miles long were observed in April 1815, and even 4 years later, these islands still hindered navigation.  As the intense heat escaped through the vent, the explosion was heard some 1,600 miles away in western Indonesia.

Up until the summer of 1816, with ash still in the upper atmosphere, the long-term consequences of the eruption finally began to take shape, causing the “Year Without a Summer” and wreaking havoc on weather patterns. The reason for the climatic changes was increased absorption of sunlight due to a veil of aerosols (consisting mostly of tiny droplets of H2SO3 acid, formed by SO2 release) that were dispersed around both hemispheres by stratospheric currents from the tall eruption column.  Global temperatures dropped by as much as 3 deg C in 1816 and recovered during the following years.