Miyake-jima

Miyake-jima
Miyake-jima of Kōzu-shima seen from
Waters	Pacific Ocean
Archipelago	Izu Islands
Geographical location	34 ° 5 '  N , 139 ° 32'  E Coordinates: 34 ° 5 '  N , 139 ° 32'  E
length	11 km
width	8 kilometers
surface	55.21 km²
Highest elevation	Oyama 815  m
Residents	2324 (April 1, 2009) 42 inhabitants / km²
main place	Miyake
Map of Miyake-jima, with Ōnohara-jima west-southwest

Miyake-jima ( Japanese 三 宅 島 ) is a volcanic island in the Pacific Ocean . Geographically it belongs to the Japanese Izu Islands and, like the entire archipelago, administratively belongs to the Tokyo Prefecture .

geography

Miyake-jima is located about 180 km south of Tokyo and 22 km north of the neighboring island of Mikura-jima , with which it forms the sub-prefecture of Miyake ( 三 宅 支 庁 , Miyake-shichō ). The island is about 11 km long, up to 8 km wide and has an area of ​​55.21 km². It is the third largest of the Izu Islands after Izu-Ōshima and Hachijō-jima .

Miyake Parish

The community Miyake ( 三宅村 , Miyake- mura , literally "village Miyake") includes not only the island of Miyake also, about 10 km west-southwest area, this small and uninhabited rock group Ōnohara-jima . In April 2009 the community had 2324 inhabitants on 55.23 km². The population density is 42 inhabitants / km². The island has several localities along the coast. The main town and seat of the municipality is Tsubota on the southeast coast.

Volcanism

Miyake-jima is included in the arch of the Izu, Bonin and Mariana Islands . Basically, the construction of the volcano was completed over 10,000 years ago. The Kuwakidaira caldera with a diameter of 3.5 kilometers in the middle of the island dates from this time . The Hatchodaira caldera with a diameter of 1.5 kilometers was created here during an eruption around 2500 years ago. Further eruptions in which basaltandesite was extracted created the stratovolcano Oyama , the highest point on the island, inside the calderas . Before 2000, it was 815 meters above sea level.

Characteristic of the eruptions of the past 600 years were fissure eruptions in which slag was ejected and lava flows emerged. If the crevices reached as far as the coast, phreatomagmatic explosions occurred , with maars , tuff rings and explosion craters.

Outbreaks occurred in the 20th century in 1940, 1962, 1983 and 2000. In 1940, 11 people died. The eruption at that time took place as well as that of 1962 from crevices in the northeast of the island. On October 3, 1983, a 4.5 kilometer long crevice opened in the southwest of the island, from which lava fountains shot up. Lava flows formed, one of which flowed south, reached the sea and triggered phreatomagmatic explosions there. Another lava flow turned west and overflowed large parts of the village of Ako, destroying around 400 houses. The approximately 1400 inhabitants of Akos were evacuated by boats and buses. Similar to the Eldfell eruption in Iceland in 1973, attempts were made to cool the lava with seawater in order to slow down its further advance. The outbreak ended after ten hours.

• Satellite images of Miyake-jima
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  May 16, 2000

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  April 1, 2001

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  November 14, 2011

On June 27, 2000, a minor submarine eruption occurred around one kilometer west of Miyake-jima . A series of earthquakes had already been registered the day before , the epicentres of which shifted over several days to the northwest towards the island of Kōzu-shima . An earthquake on July 1st with a magnitude (M _W ) of 6.1 triggered a landslide on Kōzu-shima , through which a person died. From July 8, a new caldera formed in the center of Miyake-jima, which in mid-August was 1.6 kilometers in diameter and 450 meters deep. From August 10th, phreatic and phreatomagmatic eruptions increased in the area of ​​the new caldera, producing ash and lapilli and lasting until the end of September. In an eruption on August 18, a column of eruptions rose over ten kilometers high. The series of earthquakes is interpreted as the formation of Dykes , which was penetrated by magma from the magma chamber below Miyake-jima. Then the ceiling collapsed over the magma chamber, creating the caldera.

At the end of August 2000, all around 3800 inhabitants of the island were evacuated, as it was feared that rainfalls could mobilize the ash deposits and trigger mudslides . From September the volcano emitted extraordinarily large amounts of sulfur dioxide (SO ₂ ). Emissions peaked in November 2000 at 80,000 tons per day and fell to 2000–5,000 tons per day by the end of 2004. Despite the continued high SO ₂ concentrations, the evacuation of the residents was ended in February 2005. The islanders were advised to carry respiratory masks ; there were also access restrictions in high-risk areas. Warning lights and loudspeakers were used to quickly inform the population in the event of increased SO ₂ concentrations. After 2000 there were several smaller explosive eruptions in the area of ​​the caldera, most recently in 2010.

fauna and Flora

Miyake-jima is part of the Izu Islands in the Fuji-Hakone-Izu National Park . Despite human influences and volcanic activities, the island has a great diversity of species. The Izu thrush ( Turdus celaenops ) , which only occurs on a few Izu islands, is worth mentioning .

Web links

Commons : Miyake-jima  - collection of images, videos and audio files

Commons : Miyake-mura  - collection of images, videos and audio files

• Miyake-jima in the Global Volcanism Program of the Smithsonian Institution (English)
• Miyake-jima in the Japanese Volcanoes Quaternary database (English and Japanese)
• Geol. Map

Individual evidence

1. ↑ 島 面積 . (PDF; 144 kB) (No longer available online.) Kokudo Chiriin , October 1, 2014, archived from the original on April 2, 2015 ; Retrieved July 29, 2016 (Japanese). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
2. ↑ N. Geshi, T. Shimano, T. Chiba, S. Nakada: Caldera collapse during the 2000 eruption of Miyakejima Volcano, Japan. ( Memento of January 29, 2013 in the Internet Archive ) In: Bulletin of Volcanology. 64, 2002 pp. 55–68, here p. 56 (English, PDF; 714 kB).
3. ↑ ^{a b} Miyake-jima. In: Geological Survey of Japan, AIST. Retrieved July 29, 2016 (Japanese).  in the Japanese Volcanoes Quaternary database (accessed March 6, 2013).
4. ↑ Four lava flows, four explosion craters from 10-hour eruption. Monthly report 10/1983 in the Global Volcanism Program (accessed March 6, 2013);
   Excerpt from: The 1983 Eruption of Miyakejima. In: Bulletin of the Volcanological Society of Japan. 29 (accessed March 6, 2013).
5. ^ Entry in The Significant Earthquake Database of NOAA (English, accessed on March 6, 2013).
6. ↑ Geshi, Caldera collapse , passim.
7. ↑ Robust, multifaceted eruptions from new summit crater. Monthly report 07/2000 in the Global Volcanism Program (accessed March 6, 2013).
8. ↑ Yasuhiro Ishimine: Measures Taken by Local Officials against Sulfur Dioxide Emissions from Miyakejima Volcano. at the USGS ' Hawaiian Volcano Observatory (English, PDF; 185 kB).