Earth:Izu-Tobu

Izu-Tobu
Izu-Tobu
	Izu-Tobu volcano field
	Mount Ōmuro, a symbolic pyroclastic cone of　the Izu-Tobu volcano field
Highest point
Coordinates	[ ⚑ ] : 34°53′59″N 139°05′52″E / 34.89972°N 139.09778°E
Naming
Native name	伊豆東部火山群 (Japanese)
Geography
	Izu-Tobu Izu Peninsula, Shizuoka Prefecture, Japan Izu-Tobu Izu-Tobu (Shizuoka Prefecture)
Geology
Mountain type	Pyroclastic cones
Last eruption	July 1989

Short description: Large range of volcanoes on the island of Honshu, Japan

Izu-Tobu (伊豆東部火山群, Izu Tōbu Kazangun) is a large, dominantly basaltic range of volcanoes on the east side of the Izu Peninsula which lies on the Pacific coast of the island of Honshu in Japan. The field covers a total area of 400 km². The only recorded activity was a submarine phreatic eruption, between the city of Ito and Hatsushima island, that lasted for just 10 minutes in 1989. Ito, home to 74,000 people, is known for its hot springs.

Morphology

The field covers the east side of the Izu Peninsula. It consists of several small stratovolcanoes (mostly Pleistocene in age) and overlapping pyroclastic cones, which covers 400 km² in area. There are 70 young monogenetic volcanoes on land. Kawagodaira maar, which is about 3,000 years old, produced a large Holocene eruption that sent pyroclastic flows over a wide area.

Eruptions

Distribution map

1989 eruption

The only recorded eruption was an event on 13 July 1989. Two earthquakes, on 30 June and 9 July took, place on the Izu-Tobu Volcano. On 13 July, a seismometer recorded seismicity, a research vessel, the RV Takuyo reported hearing an explosion sound from the sea floor followed by a 30-second vibration at 18:33 pm. At 18:40 pm the crew reported that the sea domed up 500 m from the vessel, then a grey-black plume rose from the area, five more domes were reported in the next 5 minutes which caused the ship to vibrate. After that seismicity declined.

This marks the only known eruptive activity at Izu-Tobu. The next day a survey using an unmanned vessel discovered a new cone 100 metres underwater. The cone was around 450 Metres wide with a summit crater 200 m in diameter. The height of the cone above the sea floor was only 10 m in height.

The University of Tokyo monitors Izu-Tobu 24 hours a day.

Distinct cones

Image	Name	Location	Type^[1]^[2]	Height	Eruption^[1]^[2]	Coordinates	Comments
01	omuro Mount Ōmuro (大室山)	Itō	Cinder cone	0580 580 m	004000 4 ka	[ ⚑ ] 34°54′11″N 139°05′40″E / 34.9031°N 139.0945°E / 34.9031; 139.0945	Lava flow formed the Jōgasaki coast.
02 (Right)	komuro Mount Komuro (小室山)	Itō	Cinder cone	0321 321 m	015000 15 ka	[ ⚑ ] 34°56′21″N 139°07′52″E / 34.9391°N 139.131°E / 34.9391; 139.131
03	ioyama Mount Io (伊雄山)	Itō	Cinder cone	0459 459 m	002700 2.7 ka	[ ⚑ ] 34°52′18″N 139°04′46″E / 34.8717°N 139.0795°E / 34.8717; 139.0795
04	togasa Mount Tōgasa (遠笠山)	Izu & Higashizu	Cinder cone	1197 1,197 m	140000 14 ka - 15 ka	[ ⚑ ] 34°52′43″N 139°01′57″E / 34.8786°N 139.0325°E / 34.8786; 139.0325	Oldest volcano in Izu-Tobu volcano field
05	kawago Kawagodaira (皮子平)	Izu	Volcanic crater	1090 approx. 1,090 m	003200 3.2 ka	[ ⚑ ] 34°51′36″N 138°58′55″E / 34.860°N 138.982°E / 34.860; 138.982
06	maruno Mount Maruno (丸野山)	Izu	Cinder cone	0697 697 m	107500 107 ka	[ ⚑ ] 34°54′40″N 139°01′26″E / 34.911°N 139.024°E / 34.911; 139.024
07	sukumo Mount Sukumo (巣雲山)	Izu	Cinder cone	0581 581 m	132000 132 ka	[ ⚑ ] 35°00′18″N 139°02′13″E / 35.005°N 139.037°E / 35.005; 139.037
08	hachikubo Mount Hachikubo (鉢窪山)	Izu	Cinder cone	0674 674 m	017000 17 ka	[ ⚑ ] 34°51′43″N 138°55′44″E / 34.862°N 138.929°E / 34.862; 138.929	Lava flow from Mount Hachikubo formed Jōren Falls.
09	maruyama Mount Maru (丸山)	Izu	Cinder cone	0938 938 m	017000 17 ka	[ ⚑ ] 34°51′18″N 138°56′20″E / 34.855°N 138.939°E / 34.855; 138.939
10	takatsuka Mount Takatsuka (高塚山)	Izunokuni	Cinder cone	0369 369 m	132000 132 ka	[ ⚑ ] 35°00′59″N 138°58′48″E / 35.0165°N 138.98°E / 35.0165; 138.98	Cinder cone was halved by quarrying.^{[citation needed]}
11	hachino Mount Hachino (鉢ノ山)	Kawazu	Cinder cone	0619 619 m	036000 36 ka	[ ⚑ ] 34°47′35″N 138°58′16″E / 34.793°N 138.971°E / 34.793; 138.971
12 (Left)	yahazu Mount Yahazu (矢筈山)	Itō	Lava dome	0816 816 m	002700 2.7 ka	[ ⚑ ] 34°53′42″N 139°03′25″E / 34.895°N 139.057°E / 34.895; 139.057
13 (Right)	anano Mount Anano (孔ノ山)	Itō	Lava dome	0660 660 m	002700 2.7 ka	[ ⚑ ] 34°54′00″N 139°03′11″E / 34.9°N 139.053°E / 34.9; 139.053
14	iwano Mount Iwano (岩ノ山)	Izu	Lava dome	0602 602 m	002700 2.7 ka	[ ⚑ ] 34°54′47″N 139°02′20″E / 34.913°N 139.039°E / 34.913; 139.039
15	ippeki Ippeki lake (一碧湖)	Itō	Maar	0185 Surface elevation 185 m^[3]	103500 103.5 ka	[ ⚑ ] 34°55′48″N 139°06′18″E / 34.93°N 139.105°E / 34.93; 139.105
16	jogasaki Jōgasaki coast (城ヶ崎海岸)	Itō	Lava flow	-	004000 4 ka	[ ⚑ ] 34°53′24″N 139°08′17″E / 34.89°N 139.138°E / 34.89; 139.138	This coast was mostly formed by lava flow from Mount Ōmuro.
17	teishi Teishi knoll (手石海丘)	Sagami Sea (off Itō)	Volcanic crater
001989 13 July 1989	[ ⚑ ] 34°59′06″N 139°07′08″E / 34.985°N 139.118889°E / 34.985; 139.118889	Youngest volcano in Izu-Tobu volcano field. Eruption video by Japan Coast Guard