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Volcanoes Under the Sea

Part of Hall of Planet Earth.

Volcanoes Under the Sea

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The longest volcano chain in the world is the 80,000-kilometer-long mid-ocean ridge system, where new ocean crust is formed and the tectonic plates - the Earth's moving outer shell - separate from each other. Unlike the great Hawaiian shield volcanoes, the volcanoes making up the ocean ridges are long and narrow. Basaltic lavas erupt mostly from fissures, or cracks, in the seafloor. Ninety percent of the Earth's eruptive activity and heat loss f