Iwo-jima volcano (Volcano Islands, Japan): new phreatomagmatic eruption

 

A new phreatomagmatic eruption took place at the volcano on 30 October.

The eruption occurred approx. 1 km off the coast of Okinahama Beach, located on the south of the island. From aerial footage, a mixture of dark black volcanic ash, lapilli, bombs and seawater were being thrown to a height of 20-30 meters every few minutes. A certain amount of lighter pumice was also present in the ash, probably representing a batch of fresh magma that had driven the explosion.

A pumice raft has been observed floating towards the other side of the island.
Phreatomagmatic activity means that erupting magma reacts with external water, e.g. ground water, lake water, sea water etc.
According to the Japan Meteorological Agency (JMA), the eruption site was affirmed at roughly the same location as happened in July-August, October and December last year. Over the past years, the volcanic activity at the volcano has caused the island to rise, actually some spots have risen more than 10 meters over the past ten years.

Ioto (硫黄島, also known as Iwo-jima) volcano is a triangular-shaped, flat, 8 km long and up to 4.5 wide volcanic island stretching NE-SW. It is surrounded by steep cliffs under the sea, which belong to a 9-km-wide submarine caldera. Parts of the caldera have been experiencing remarkably strong uplift (up to more than 1 meter per year and averaging 25 cm / year over several centuries). There is strong hydrothermal activity at present, at fumaroles along a NE-SW zone cutting through Moto-yama. Many phreatic eruptions occurred in historic times, mostly from vents on the west and NW sides of the island.