Plinian/Vesuvian eruptions are marked by columns of volcanic debris and hot gases ejected high into the stratosphere, the second layer of Earth's atmosphere. The key characteristics are the ejection of a large amount of pumice and very powerful continuous gas-driven eruptions.
Short eruptions can end in less than a day, but longer events can continue for several days or months. The longer eruptions begin with production of clouds of volcanic ash, sometimes with pyroclastic surges. The amount of magma ejected can be so large that it depletes the magma chamber below, causing the top of the volcano to collapse, resulting in a caldera. Fine ash and pulverized pumice can be deposited over large areas. Plinian eruptions are often accompanied by loud sounds. The sudden discharge of electrical charges accumulated in the air around the ascending column of volcanic ashes also often causes lightning strikes, as depicted by the English geologist George Julius Poulett Scrope in his painting of 1822 or observed during 2022 Hunga Tonga–Hunga Ha'apai eruption and tsunami.[2]
The lava is usually dacitic or rhyolitic, rich in silica. Basaltic, low-silica lavas rarely produce Plinian eruptions unless specific conditions are met (low magma water content <2%, moderate temperature, and rapid crystallization);[3] a recent basaltic example is the 1886 eruption of Mount Tarawera on New Zealand's North Island.[4]
On August 24th, about one in the afternoon, my mother desired him to observe a cloud which appeared of a very unusual size and shape. He had just taken a turn in the sun and, after bathing himself in cold water, and making a light luncheon, gone back to his books: he immediately arose and went out upon a rising ground from whence he might get a better sight of this very uncommon appearance. A cloud, from which mountain was uncertain, at this distance (but it was found afterwards to come from Mount Vesuvius), was ascending, the appearance of 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. This phenomenon seemed to a man of such learning and research as my uncle extraordinary and worth further looking into.
— Sixth Book of Letters, Letter 16, translation by William Melmoth
Pliny the Elder set out to rescue the victims from their perilous position on the shore of the Bay of Naples, and launched his galleys, crossing the bay to Stabiae (near the modern town of Castellammare di Stabia). Pliny the Younger provided an account of his death, and suggested that he collapsed and died through inhaling poisonous gases emitted from the volcano. His body was found interred under the ashes of the eruption with no apparent injuries on 26 August, after the plume had dispersed, confirming asphyxiation or poisoning.
Examples
April 21, 1990, eruption cloud from Redoubt Volcano as viewed to the west from the Kenai Peninsula (more than 60 km from the volcano's summit)April 2015, subplinian eruption of Calbuco
In 1980, volcanologist George P. L. Walker proposed the Hatepe eruption as the representative of a new class called ultra-Plinian deposits, based on its exceptional dispersive power and eruptive column height.[8] A dispersal index of 50,000 square kilometres (19,000 sq mi) has been proposed as a cutoff for an ultra-Plinian eruption.[8] In the criteria of Volcanic Explosivity Index, recognizing an eruption as ultra-Plinian would make it at least VEI-5 or higher.[9]
The once unequivocal ultra-Plinian classification of the Hatepe eruption has been called into question, with recent evidence showing that it is an artifact of an unrecognized shift in the wind field rather than extreme eruptive vigor.[16][17]
^Enlightenment activities for improvement on disasters. From 23–27 January 2006 Tarumae volcano [eruption], Japan, 4 cities near volcanoes.[full citation needed]
^Williams, Stanley N.; Self, Stephen (1983). "The October 1902 plinian eruption of Santa Maria volcano, Guatemala". Journal of Volcanology and Geothermal Research. 16 (1–2): 33–56. doi:10.1016/0377-0273(83)90083-5.
^Self, Stephen; Wolff, John ; Wright, John (2021-12). Tsankawi Pumice Fall Unit B, a Very Widespread and Powerfully Emplaced Plinian Deposit. AGU Fall Meeting 2021.
