Dienstag, Apr 23, 2013
The earthquake swarm that started on 17 April and included a magnitude 5.6 quake has been decreasing and remained at the same depths at around 10-15 km just west off the island. ... [mehr]
Freitag, Apr 19, 2013
A strong earthquake swarm, presumably caused by a magmatic intrusion, has started Wednesday at Miyake volcano in the Japanese Izu Islands. ... [mehr]
Miyake-shima VulkanMiyake-jima (三宅島 Miyakejima) is an active stratovolcano in the northern Izu Islands, about 200 km south of Tokyo. It forms a 8 km diameter circular island and is one of the most frequently active volcanoes in the island chain. It typically erupts every 10-30 years. The last series of eruptions started in June 2000 after 17 years of repose.
The volcano has had many eruptions both from summit and flank vents, including submarine eruptions. Many eruptions have caused considerable damage to the island.
Beschreibung:The island of Miyake-jima is the submerged part of a low-angle stratovolcano that rises about 1100 m from the sea floor. It is mainly basaltic and has small summit calderas, one which is 3.5 km wide and was formed during a major explosive eruption about 2500 years ago.
There are numerous fissure vents on its flanks and flank cones, craters and maars near the coast.
A 300 years long pause in activity ended in 1469. Since then, activity was mostly from flank fissures and sometimes accompanied by small summit eruptions. A new eruptive phase started in 2000, during which a new 1.6 km wide summit caldera formed by repeated subsidence of the crater.
(Source: Smithsonian / GVP volcano information)
2000 eruptions and formation of a new summit caldera
After a repose interval of 17 years, a series of new eruptions started at Miyakejima in 2000. The eruption was preceded by strong deformation and intense earthquake swarms: Between 26 June and 21 July 2000 there were 17,500 earthquakes, including 5,480 which could be felt by residents. A magnitude 6.4 earthquake on 1 July 2000 killed one person by rockfall on Kozu-shima.
An explosive eruption occurred on 7 July 2000, prompting the evacuation of the island on 1 September, and people were first allowed to return on 1 February 2005. During the period 8 July-31 August 2000, the volcano produced large phreatic eruptions, ash plumes up to 15 km high, pyroclastic flows, ash fall and a series of gradual concentric crater collapses. By October 2000, a new 1.6-km-wide summit caldera had slowly formed by subsidence and the crater floor had dropped to only 230 m above sea level.
Source: Smithsonian / GVP monthly reports