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Fukutoku-Okanoba Submarine Volcano

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    2nd Sep, 2021


Fukutoku-Okanoba Submarine Volcano, an underwater volcano that exploded in the Pacific Ocean, off Japan, mid-August, poses a risk to the passage of planes and ships.

About Fukutoku-Okanoba volcano-

  • The Fukutoku-Okanoba volcano is situated about 25 metres (80 feet) below the sea five kilometres north of Japan’s South Iwo Jima Island.

  • The plume reached a height of 16 kilometres above the surface, posing a risk to the passage of planes and ships.
    • The eruption could have happened in shallow water due to which the ash plume had reached such a height.
    • The normal cruising altitude of aircraft is about 10 kilometres.
  • Plume went straight from being a submarine event to an eruption cloud reaching the lower boundary of the Stratosphere, this is not very common for this type of volcano.
    • ??Normally lower-level plumes are seen from submarine eruptions.
    • Eruption and submarine hydrothermal activities often cause water discoloration in the area, and during eruption, the volcano has built several temporary new islands.

Submarine volcanoes

  • Submarine volcanoes are erupting basaltic lavas and new crust material is actively formed with substantial piles of pillow lavas.
  • Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. 
  • Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. 
  • The volcanoes at mid-ocean ridges alone are estimated to account for 75% of the magma output on Earth.

Floating rafts of Pumice

  • Several floating rafts of pumice drifting northwest of the eruption site were also witnessed.


  • Pumice is one of the only types of rock that can float due to a combination of surface tension and the many air-filled holes and cavities found within the rock.
  • Rafts of the rock can drift in the ocean for months or even years.
  • As they drift, the volcanic rocks often pick up various forms of life, ranging from bryozoans to barnacles to crabs.