The Seafloor Spreading Hypothesis
The seafloor spreading hypothesis brought all ..
All of the early evidence for continental drift came from the continents. But if the continental crust moved, then the ocean crust must also move also. Evidence for the movement of the seafloor came from a hypothesis by Harry Hess of Princeton University.
the seafloor spreading hypothesis.
In 1915, Wegener proposed his continental drift theory. He said that the continents floated atop the mantle-a heavier, denser layer of rocks deep within the earth. Wegener predicted that heat rising within the hot mantle created currents of partially melted rocks that could move the continents around the earths surface.
Like many revolutionary theories, Wegeners was not initially accepted by scientists. The good fit of the continents and the fossil and rock evidence did not provide enough proof. For decades afterward, scientists still did not understand how massive continents could be transported across the face of the Earth, and they had no evidence of any process that could cause continents to move.
In the 1950s and 1960s, marine geologists such as Bruce Heezen, Marie Tharp, and Henry Menard used data from echo sounders to map ocean ridges in the North Atlantic and the Pacific. They noticed first that these ridges stretched on for thousands of kilometers in long, continuous mountain chains that wound around the Earths surface, almost like the stitches on a baseball. The scientists also observed that the crest of the ridges had a topography that closely resembled volcanic rift zones on land. At their crests, they had V-shaped central valleys with steep faults on either side. This evidence led early marine geologists to deduce that the mid-ocean ridges were formed by seafloor volcanoes.