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What evidence from heat flow supports seafloor spreading?

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Earth's lithosphere and upper mantle — oceanic crust A cross section of Earth's outer layers, from the crust through the lower mantle.

Evidence from heat flow measurements provides significant support for the theory of seafloor spreading. While heat flow through bottom sediments is generally comparable to that observed on continents, measurements taken at mid-ocean ridges reveal values that are three to four times higher than the normal rate.12

These anomalously high heat flow values are interpreted as evidence of molten material welling up from Earth’s mantle near the ridge crests. As this magma cools, it forms new oceanic crust that is pushed laterally away from the ridge axis. Furthermore, the subsequent cooling and thermal contraction of this crust as it moves away from the spreading center explains the observed relationship between ocean depth and the age of the seafloor.12