is a large, dominantly

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

ic range of volcanoes on the east side of the

Izu Peninsula The is a mountainous peninsula with a deeply indented coastline to the west of Tokyo on the Pacific Ocean, Pacific coast of the island of Honshu, Japan, the largest of the four main islands of Japan. Formerly known as Izu Province, Izu peninsu ...

which lies on the

Pacific coast Pacific coast may be used to reference any coastline that borders the Pacific Ocean. Geography Americas North America Countries on the western side of North America have a Pacific coast as their western or south-western border. One of th ...

of the island of

Honshu , historically known as , is the largest of the four main islands of Japan. It lies between the Pacific Ocean (east) and the Sea of Japan (west). It is the list of islands by area, seventh-largest island in the world, and the list of islands by ...

in Japan. The field covers a total area of 400 km². The only recorded activity was a submarine

phreatic eruption A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evap ...

, between the city of

Ito Ito, Itō or Itoh may refer to: Places * Ito Island, an island of Milne Bay Province, Papua New Guinea * Ito Airport, an airport in the Democratic Republic of the Congo * Ito District, Wakayama, a district located in Wakayama Prefecture, Japa ...

and Hatsushima island, that lasted for just 10 minutes in 1989. Ito, home to 74,000 people, is known for its

hot spring A hot spring, hydrothermal spring, or geothermal spring is a Spring (hydrology), spring produced by the emergence of Geothermal activity, geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow ...

Morphology

The field covers the east side of the Izu Peninsula. It consists of several small

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

es (mostly

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

in age) and overlapping

pyroclastic cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

s, which covers 400 km² in area. There are 70 young

monogenetic volcano A monogenetic volcanic field is a type of volcanic field consisting of a group of small monogenetic volcanoes, each of which erupts only once, as opposed to polygenetic volcanoes, which erupt repeatedly over a period of time. The small monogenetic ...

es on land. Kawagodaira

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

, which is about 3,000 years old, produced a large

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

eruption that sent pyroclastic flows over a wide area.

Eruptions

1989 eruption

The only recorded eruption was an event on 13 July 1989. Two

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s, 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

References

*
Volcanolive.com

External links