Volcanic winter in the context of "Hydroxide"

The Minoan eruption was a catastrophic volcanic eruption that devastated the Aegean island of Thera (also called Santorini) circa 1600 BC. It destroyed the Minoan settlement at Akrotiri, as well as communities and agricultural areas on nearby islands and the coast of Crete with subsequent earthquakes and tsunamis. With a Volcanic Explosivity Index (VEI) of 7, it resulted in the ejection of approximately 28–41 km (6.7–9.8 cu mi) of dense-rock equivalent (DRE), the eruption was one of the largest volcanic events in human history. Because tephra from the Minoan eruption serves as a marker horizon in nearly all archaeological sites in the Eastern Mediterranean, its precise date is of high importance and has been fiercely debated among archaeologists and volcanologists for decades, without coming to a definite conclusion.

Although there are no clear ancient records of the eruption, its plume and volcanic lightning may have been described in the Egyptian Tempest Stele. The Chinese Bamboo Annals reported unusual yellow skies and summer frost at the beginning of the Shang dynasty, which may have been a consequence of volcanic winter (similar to 1816, the Year Without a Summer, after the 1815 eruption of Mount Tambora).

An eruption column or eruption plume is a cloud of super-heated ash and tephra suspended in gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or plume that may rise many kilometers into the air above the vent of the volcano. In the most explosive eruptions, the eruption column may rise over 40 km (25 mi), penetrating the stratosphere. Injection of aerosols into the stratosphere by volcanoes is a major cause of short-term climate change.

A common occurrence in explosive eruptions is column collapse when the eruption column is or becomes too dense to be lifted high into the sky by air convection, and instead falls down the slopes of the volcano to form pyroclastic flows or surges (although the latter is less dense). On some occasions, if the material is not dense enough to fall, it may create pyrocumulonimbus clouds.

The year 1816 is known as the Year Without a Summer because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.7–1 °F). Summer temperatures in Europe that year were the coldest of any on record between 1766 and 2000, resulting in crop failures and major food shortages across the Northern Hemisphere.

Evidence suggests that the anomaly was predominantly a volcanic winter event caused by the massive 1815 eruption of Mount Tambora in April in modern-day Indonesia (commonly referred to as the Dutch East Indies at the time). This eruption was the largest in at least 1,300 years (after the hypothesized eruption causing the volcanic winter of 536); its effect on the climate may have been exacerbated by the 1814 eruption of Mayon in the Philippines. The significant amount of volcanic ash and gases released into the atmosphere blocked sunlight, leading to global cooling.

The volcanic winter of 536 was among the most severe and protracted episodes of climatic cooling in the Northern Hemisphere in the last two thousand years. The volcanic winter was caused by at least three eruptions of uncertain origin, with several possible locations proposed in various continents. In early AD 536 (or possibly late 535), an eruption ejected great amounts of sulfate aerosols into the atmosphere, reducing the solar radiation reaching the Earth's surface and cooling the atmosphere for several years. In March 536, Constantinople began experiencing darkened skies and lower temperatures.

Summer temperatures in 536 fell by as much as 2.5 °C (4.5 °F) below normal in Europe. The lingering effect of the volcanic winter of 536 was augmented in the years 539 and 540, when another volcanic eruption caused summer temperatures to decline as much as 2.7 °C (4.9 °F) below normal in Europe. There is evidence of still another volcanic eruption in 547 that would have extended the cool period. The volcanic eruptions caused crop failures, and were accompanied by the Plague of Justinian, famine, and millions of deaths and initiated the Late Antique Little Ice Age, which lasted from 536 to 660.

The Russian famine of 1601–1603, Russia's worst famine in terms of proportional effect on the population, killed perhaps two million people: about 30% of the Russian people. The famine compounded the Time of Troubles (1598–1613), when the Tsardom of Russia was unsettled politically and was later invaded (1605–1618) by the Polish–Lithuanian Commonwealth. The many deaths contributed to social disruption. The famine resulted from a volcanic winter, a series of worldwide record cold winters and crop disruption, which geologists in 2008 linked to the 1600 volcanic eruption of Huaynaputina in Peru.

Mount Okmok is a volcano on eastern Umnak Island, in the central-eastern Aleutian Islands of Alaska. Part of the Aleutian Volcanic Arc, it was formed by the subduction of the oceanic Pacific Plate under the North American Plate. Okmok is a large shield volcano capped by a 10-kilometer (6.2 mi) wide caldera. The caldera contains numerous cinder cones, their lava flows, and a few lakes. Okmok erupts mainly basaltic lava, mostly from the cones within the caldera.

Activity began in the Pleistocene. Two large caldera-forming eruptions took place during the Holocene, with a volcanic explosivity index (VEI) of 6; the second of these occurred in 43 BCE and caused a volcanic winter that might have changed the history of Egypt. After this second caldera-forming eruption a crater lake formed in the caldera, and drained in one of the largest known floods of the Holocene. Okmok is one of the most active volcanoes of North America; numerous eruptions have produced lava flows within the caldera, and the 1817 eruption destroyed an Aleut village.