The Volcano
Sakurajima is one of the most active volcanoes in the world and can erupt more than a thousand times a year, spewing ash kilometers above the volcano. Sakurajima is a stratovolcano, one of the 16 Decade Volcanoes, and a former island in Kagoshima Prefecture in Kyushu, Japan. In 1914 an eruption caused the island to be connected with the Osumi Peninsula. It's summit is split into three peaks, Kita-dake, Naka-dake, and Minami-dake.About 5,000 people live on the volcano, taking advantage of the fertile soil. About 600,000 people live in Kagoshima, a city that lies 5 miles from Sakurajima.
Tectonic Setting
A volcano is just a vent for magma and gases to escape through. Sakurajima rests on the southern island of Japan, known as Kyushu. Japan rests along the Eurasian Plate, a continental plate, coming in contact with the Philippine plate, an oceanic plate. These plates rest in a subduction zone, meaning it's a convergent boundary. The two plates are colliding with eachother. When that happens, one plate can slide under the other. The denser oceanic crust subducts underneath the less dense continental crust. This causes the mantle underneath to melt. The magma pushes upward, melting more rock. The hot magma collects under earth's crust. If the pressure is high enough or a crack opens in the crust, the magma spews out.
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History
Construction of the volcano is thought to have begun about 13,000 years ago at the southern perimeter of the Aira Caldera which formed as a result of a massive eruption approximately 22,000 years ago. The Sakurajima volcano is a post-caldera cone of the Aira caldera, located at the northern part of Kagoshima Bay. The first volcanic birth in the Aira Caldera was Kita-dake (North peak). It had erupted frequently until approximately 5,000 years ago when it became dormant. 500 years after that, Minami-dake (South peak) was created in an overlapping fashion next to Kita-dake. Minami-dake has been and continues to be vigorously active to this day.
Before 1955, the volcano exploded every few hundred years, blasting in 1471, in 1779 and in 1914, for example. After 1955, Sakurajima started spitting out small amounts of lava and ash almost daily, with occasional pauses or larger blasts. Researchers suspect the volcano's constant eruptions are due to a steady stream of magma feeding its volcanic vents, like a constantly running underground pipe. At other volcanoes, magma may arrive in pulses, like a faucet turning on and off. On August 18, Sakurajima erupted for the 500th time this year.
Before 1955, the volcano exploded every few hundred years, blasting in 1471, in 1779 and in 1914, for example. After 1955, Sakurajima started spitting out small amounts of lava and ash almost daily, with occasional pauses or larger blasts. Researchers suspect the volcano's constant eruptions are due to a steady stream of magma feeding its volcanic vents, like a constantly running underground pipe. At other volcanoes, magma may arrive in pulses, like a faucet turning on and off. On August 18, Sakurajima erupted for the 500th time this year.
Taisho Eruption
On January 12, 1914 Sakurajima erupted in what was the most powerful eruption to hit Japan in the 20th century. The day before the eruption most of the residents had fled, due to several large earthquakes, warning them that the once-dormant volcano was about to erupt.
Approximately 10 billion tons of lava flowed out, filling the Seto straight between the island and the mainland, connecting them and turning Sakura Island into a peninsula. Volcanic ash covered the entire area. Some residents failed to evacuate, and some attempted to swim in the cold mid-winter sea, eventually freezing to death. Approximately 8 hours after the great |
eruption, an earthquake with a magnitude of 7.1 on the Richter scale occurred. This caused great damage in Kagoshima City destroying houses and collapsing clay walls. Surprisingly, despite how large the eruption was, there were only 28 deaths (not including the deaths caused by earthquakes) and $40,000 in damage.
The website Volcano Discovery gives frequent updates of Sakurajima's activity.
http://www.volcanodiscovery.com/sakurajima/news.html
http://www.volcanodiscovery.com/sakurajima/news.html