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Earth Sciences
Plate Tectonics

What is the theory of Seafloor spreading?


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May 18, 2011 1:31AM

The theory of seafloor spreading was proposed by Harry H. Hess, an American geophysicist, in 1960. According to Hess, seafloor spreading is where two tectonic plates move apart and the ocean floor spreads out. When two tectonic plates spread apart they break. Magma then forces its way up through the cracks in an underwater volcano. When the magma hits the water, it cools and forms ridges along the plates that are pulling apart. In a normal volcano, the magma would pour down the sides and build up, but the since the plates are pulling apart underwater, the magma is more like forming a bridge. However, this bridge has valleys and mountains and is known as an oceanic ridge. The material being formed is known as constructive because a new ocean floor is actually being formed as a result of the process.