Aira Caldera
Encyclopedia
Aira Caldera is a gigantic volcanic caldera
in the south of the island of Kyūshū
, Japan
. The caldera was created by a massive eruption, approximately 22,000 years ago. Eruption of voluminous pyroclastic flow
s accompanied the formation of the 17 × 23 km-wide Aira caldera. Together with a large pumice
fall, these amounted to more than 400 km3 of tephra
(VEI 7
).
The major city of Kagoshima and the 13,000-year-old Sakurajima
volcano lie within the caldera. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay
.
Caldera
A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
in the south of the island of Kyūshū
Kyushu
is the third largest island of Japan and most southwesterly of its four main islands. Its alternate ancient names include , , and . The historical regional name is referred to Kyushu and its surrounding islands....
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. The caldera was created by a massive eruption, approximately 22,000 years ago. Eruption of voluminous pyroclastic flow
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...
s accompanied the formation of the 17 × 23 km-wide Aira caldera. Together with a large pumice
Pumice
Pumice is a textural term for a volcanic rock that is a solidified frothy lava typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. This unusual formation is due to the simultaneous actions of rapid...
fall, these amounted to more than 400 km3 of tephra
Tephra
200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....
(VEI 7
Volcanic Explosivity Index
The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
).
The major city of Kagoshima and the 13,000-year-old Sakurajima
Sakurajima
, also romanized as Sakurashima or Sakura-jima, is an active composite volcano and a former island of the same name in Kagoshima Prefecture in Kyūshū, Japan...
volcano lie within the caldera. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay
Kagoshima Bay
is a deep inlet on the coast of Japan.Kagoshima Bay is on the south coast of the island of Kyūshū. The port city of Kagoshima and its well-protected harbor lie on the bays western coast....
.