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Ogasawara island

14th November, 2023 Geography

Ogasawara island

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  • After an undersea volcano erupted, a new island appeared in Japan's Ogasawara Island group.


Facts about the Ogasawara Islands

  • The Ogasawara Islands are located in the Pacific Ocean's northwestern hemisphere.
  • It is also known as the Bonin Islands.
  • It is a volcanic arc with around 30 islands and islets.
  • Subtropical forest types and sclerophyllous shrublands dominate the environment, which is flanked by rocky cliffs.
  • It is a well-known UNESCO World Heritage site in Japan.

About Phreatomagmatic eruption

  • A phreatomagmatic eruption built a new island near Japan's Ogasawara Island group.
  • It is a magmatic and hydrothermal eruption.
  • It usually interacts explosively, resulting in the simultaneous ejection of steam and pyroclastic debris.
  • The same mechanism produces phreatomagmatic ash in a wide range of basic and acidic compositions.
  • It forms a blocky, homogeneous crust with a low vesicle content.
  • Deposits from phreatomagmatic eruptions are expected to be more fine-grained and better categorized than deposits from magmatic eruptions.
  • This is due to the increased fragmentation of phreatomagmatic eruptions.

How do new islands continue to appear near Japan?

  • Phreatomagmatic eruptions, which occur when magma interacts with saltwater and produces explosive bursts of steam and ash, are primarily responsible for the formation of these islands.
  • After that, the volcanic material collected on the shallow substrate and rose above the water surface, forming an island.

Why do continuous volcanic eruptions occur near Japan?

  • Active volcanism is the result of several continental plates colliding.
  • The Eurasian, North American, Philippine, and Pacific plates all clash in a narrow area near Japan.
  • Geographic location- Japan is placed on the "Ring of fire," which contains 111 of the world's approximately 1500 active volcanoes.

Earlier emergence of islands due to volcanic eruption

  • In 2013, an eruption at Nishinoshima in the Pacific Ocean south of Tokyo led to the formation of a new island.
  • In 2013, a small island surfaced from the seabed after a massive 7.7-magnitude earthquake in Pakistan.
  • In 2015, a new island was formed as a result of a month-long eruption of a submarine volcano off the coast of Tonga.


Discuss the significance and environmental implications of underwater volcanic eruptions. How do these events impact marine ecosystems, climate, and geological processes?