|Na Pali Coast on Kauai island (stock image). It has long been accepted that as Earth's plates move over fixed hot spots in its underlying mantle, resulting eruptions create chains of now extinct underwater volcanoes or 'seamounts'. One of the most famous is the Hawaiian-Emperor chain in the northern Pacific Ocean. The seamounts of that chain are composed mainly of ocean island basalts -- the type of lava that erupts above hot spots.|
Geoscientists have helped prove that some of the ocean's underwater volcanoes did not erupt from hot spots in the Earth's mantle but instead formed from cracks or fractures in the oceanic crust.