What are the crater dimensions of Oshima?

What are the crater dimensions of Oshima?

The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Mihara-yama, that has been the site of numerous historical eruptions.

What is the composition of the Oshima volcano?

The volcano, composed mainly of basalt, is between 49.5 and 58.0 wt %.. Miharayama summit A-Crater taken from the northeast on November 17, 1986. Courtesy of Osamu Oshima.

What is volume in volcanoes?

A widely accepted measure of the size of an eruption is the volume of lava ejected as pumice and ash (tephra) during an explosive phase or the volume of lava extruded during an effusive phase. Eruption volumes are commonly expressed in cubic kilometers (km3). One km3 is roughly equivalent to 0.24 cubic mile.

What type of eruptions does Oshima produce?

A violent explosion and landsliding from the Nishi-yama cone accompanied a large tectonic earthquake and a major tsunami that killed 1,475 people, most on the W coast of the Oshima Peninsula. Subsequent eruptions through early 1742 produced a new central cone and lava flows.

What tectonic plate is Oshima on?

1. Oshima-Oshima (solid triangle) is located on the boundary be- tween the Eurasian (or Amurean) and North American (or Okhotsk) plates, where large (M>7.5) tsunamigenic earthquakes have occurred since the 19th century.

When was the last time Oshima erupted?

Ten minor explosive eruptions have occurred at Oshima since 1962, the latest [in 1974]. Table 1. Number of felt and recorded earthquakes at Oshima, 30 October-17 November 1977….November 1977 (NSEB 02:11) Cite this Report.

Date Felt Earthquakes Recorded Earthquakes
17 Nov 1977 3 242

How does the volume of an eruption affect the area?

A series of small eruptions usually builds up mounds close to the vent, whereas large-volume eruptions tend to disperse their products over a greater distance. The chemical composition of magma affects its physical properties, which in turn have a major influence on the landform built by a volcanic eruption.

How is a volcano measured?

A scale is used to help measure and keep track of eruptions. People who study volcanoes use this scale, known as the Volcanic Explosive Index, or VEI. This scale works just like the Richter scale, which measures the amplitude of earthquakes.

Is the Oshima volcano active?

The Izu-Oshima volcano is one of the most active volcanoes in Japan, and has generated relatively large-scale eruptions every 30–40 years for the past 200 years. As more than 30 years have passed since the last eruptions in 1986–87, volcanic activity is expected to resume in the near future.

How big is the Oshima volcano in Japan?

Oshima volcano (伊豆大島 Izu-ōshima) is the northernmost of the Izu islands of Japan, and one of the world’s most active volcanoes. It is a mostly submerged stratovolcano that forms an 11 x 13 km island.

How did the Oshima volcano cause a tsunami?

The western cone partially collapsed during an eruption in 1741, creating a large horseshoe-shaped caldera breached to the north and extending from the summit down to the sea floor at the base of the volcano. This event produced a mostly submarine debris avalanche that traveled 16 km distance, and triggered a large tsunami.

When did the Nishi yama volcano erupt in Japan?

An eruption in August 1741 produced heavy ashfall on the Hokkaido mainland. A violent explosion and landsliding from the Nishi-yama cone accompanied a large tectonic earthquake and a major tsunami that killed 1,475 people, most on the W coast of the Oshima Peninsula.

Where are the volcanoes in the Japan Sea?

This small island 55 km W of Hokkaido in the Japan Sea consists of two coalescing volcanoes. An eruption in August 1741 produced heavy ashfall on the Hokkaido mainland.