   #copyright

Sakurajima

2007 Schools Wikipedia Selection. Related subjects: Geography of Asia

                                                                Sakurajima
                            Landsat satellite image of Sakurajima volcano
                               Elevation:               1,117 m (3,665 ft)
                             Coordinates:                 31°35′N 130°39′E
                                Location:                    Kyūshū, Japan
                                    Type:                    Stratovolcano
                           Last eruption:                          Ongoing

   Sakurajima (桜島) is an active volcano and a former island (now connected
   to the mainland) of the same name in Kagoshima Prefecture in Kyūshū,
   Japan. The north peak (its highest peak) rises 1,117 m above sea level.
   The mountain stands in the part of Kagoshima Bay known as Nishikie Bay.
   The island is part of the city of Kagoshima.

   In 1914, a great eruption occurred, burying the straits with lava, and
   connecting the former island to the Osumi Peninsula, so that Sakurajima
   is no longer an island. The volcanic activity still continues, dropping
   large amounts of volcanic ash on the surroundings. Earlier eruptions
   built the white sands highlands in the region.

Geological history

   Sakurajima is located in the Aira caldera, formed in an enormous
   eruption 22,000 years ago. Several hundred cubic kilometres of ash and
   pumice were ejected, causing the magma chamber underneath the erupting
   vents to collapse. The resulting caldera is over 20 km across. Tephra
   fell as far as 1000 km from the volcano.

   Sakurajima was formed by later activity within the caldera, beginning
   about 13,000 years ago. It lies about 8 km south of the centre of the
   caldera. Its first eruption in recorded history occurred in AD708. Most
   of its eruptions are strombolian, affecting only the summit areas, but
   larger plinian eruptions have occurred in 1471-1476, 1779-1782 and
   1914.

1914 eruption

   Sakurajima
   Enlarge
   Sakurajima
   Sakurajima ferry
   Enlarge
   Sakurajima ferry

   The 1914 eruption was particularly powerful, and during the eruption
   lava flows filled in the narrow strait between the island and the
   mainland, converting it into a peninsula. Before 1914, the volcano had
   been dormant for over a century.

   The eruption began on January 11, 1914. Almost all residents had left
   the island in the previous days, in response to several large
   earthquakes which warned them that an eruption was imminent. Initially,
   the eruption had been very explosive, generating eruption columns and
   pyroclastic flows, but after a very large earthquake on January 13
   which killed 35 people, it became effusive, generating a large lava
   flow.

   Lava flows are rare in Japan—the high silica content of the magmas
   there mean that explosive eruptions are far more common. But the lava
   flows at Sakurajima continued for months. The island grew, engulfing
   several smaller islands nearby, and eventually becoming connected to
   the mainland by a narrow isthmus. Parts of Kagoshima Bay were
   significantly shallowed, and tides were affected, becoming higher as a
   result.

   During the final stages of the eruption, the centre of the Aira Caldera
   sank by about two feet (0.6 m), due to subsidence caused by the
   emptying out of the underlying magma chamber. The fact that the
   subsidence occurred at the centre of the caldera rather than directly
   underneath Sakurajima showed that the volcano draws its magma from the
   same reservoir that fed the ancient caldera-forming eruption.

Current activity

   Space radar image of Sakurajima. The volcano lies within the bay formed
   by the Aira caldera
   Enlarge
   Space radar image of Sakurajima. The volcano lies within the bay formed
   by the Aira caldera

   The volcano resumed activity in 1955, and has been erupting almost
   constantly ever since. Thousands of small explosions occur each year,
   throwing ash to heights of up to a few kilometres above the mountain.
   The Sakurajima Volcano Observatory was set up in 1960 to monitor the
   eruptions, and today Sakurajima is one of the best-studied volcanoes in
   the world.

   Monitoring of the volcano and predictions of large eruptions are
   particularly important because of its location in a densely populated
   area, with Kagoshima's 600,000 people just a few kilometres from the
   volcano. The city conducts regular evacuation drills, and a number of
   shelters have been built where people can take refuge from falling
   volcanic debris.

   In light of the dangers it presents to nearby populations, Sakurajima
   was designated a Decade Volcano in 1991, identifying it as worthy of
   particular study as part of the United Nations' International Decade
   for Natural Disaster Reduction.
   Retrieved from " http://en.wikipedia.org/wiki/Sakurajima"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
