Question

In addition to paleomagnetism, what other evidence was needed to determine the rate of seafloor spreading? *MEDAL AND FAN AWARDED*

A. the age of each strip of rock
B. the strength of the magnetic field

Answer 1

Abundant evidence supports the major contentions of the seafloor-spreading theory. First, samples of the deep ocean floor show that basaltic oceanic crust and overlying sediment become progressively younger as the mid-ocean ridge is approached, and the sediment cover is thinner near the ridge. Second, the rock making up the ocean floor is considerably younger than the continents, with no samples found over 200 million years old, as contrasted with maximum ages of over 3 billion years for the continental rocks. This confirms that older ocean crust has been reabsorbed in ocean trench systems.