Mount Unzen is definitely part of the active volcanic groups of, many different stratovolcanoes, near the city of Shimabara, Nagasaki on the island of Kyushu Japan's southern main island.
In 1792, the collapse of one of its many lava domes triggered a mega tsunami that killed 14,600 people in Japan's worst volcanic-related eruption. The volcano was most recently active from 1990 to 1995, and a large eruption in 1991 generated a pyroclastic flow that killed about 50 people, including a group of volcanologists.
Its highest peaks are Fugen-Dake at 1,400metres and Heisei-shinzan at 1,500 metres . The latter emerged during the eruptions of the early, eponymous Heisei era.Mount Unzen is part of Shimabara Peninsula, which has seen extensive volcanic areas from over millions of years. The oldest volcanic areas in the region date from over 6 million years ago, and excessive eruptions occurred over the whole peninsula between 2.5 and 0.5 million years ago.
The origins of the Unzen are traced to the formation, through crustal faulting. This caused parts of the peninsula to downgrade by up to 1,000 metres below sea level and may have caused eruptive activity to localize at one site inside the graben. Eruptions of dacitic lava began from a site slightly to the south of today's Mount Unzen and migrated north over time.…show more content… Later eruptions over the following 150,000 years filled in much of the graben. Initially, activity was dominated by blocky andesitic lava and ash flows, changing to dacitic pumice flows and airfall deposits from 500,000 to 400,000 years ago. The period from 400,000 to 300,000 years ago saw the emplacement of large areas flow and lava deposits; these form the major part of the volcanic fan surrounding the volcano. Beginning 300,000 to 150,000 years ago, deposits were laid down, suggesting the subsidence of the volcano into its graben was rapid during this
