This category of volcanic eruptions is characterized as the largest and most violent put of all types of eruption. It is caused by the fragmentation of gassy magma, and associated with very viscous magmas (dacite and rhyolite). Plinian type of eruptions release enormous amounts of energy and create eruption columns of gas and ash that can rise up to 50 km (35 miles) high at speeds of hundreds of meters per second. Ash from an eruption column can drift or be blown hundreds or thousands of miles away from the volcano. The eruption columns are usually shaped like a mushroom (similar to a nuclear explosion) or an Italian pine tree. This type of eruption is called Plinian because it is named after Pliny the Younger, the witness of the largest catastrophic event in 79 A.D. (Ball, J.).
1.4. Duration of the eruption.
According to the historical evidence of Pliny the Younger, tons of pumice, rock and ash that Vesuvius pumped out over a 25-hour period, combined with the evidence left in Pompeii, indicates that about 2,000 residents of Pompeii survived the initial eruption of Vesuvius on August 24. It was the following morning when another, more powerful eruption killed everyone in an instant. When rain mixed with the ash, it formed a sort of concrete, preserving the city. The town of Herculaneum was also buried on August 25, but by a mudslide set off by the eruption and accompanying tremors (this day in history).
1.5. The main causes and reasons of the volcano eruption .
Scientists had a multiple attempts to explain where the roots of the catastrophic disaster coming from. Based on the data of the soil reserve prior to the main event, it can be pointed out that there were multiple small to moderate size eruptions that occurred before the 79 A.D. Thus, eruptions creating 2.2 m thick layers of volcanic ash represents the final period of volcano repose that lasted 700 years. (Jashemski, Meyer, 2002). It is known that the longer the repose of the volcano the higher the magnitude of the eruption.