Seafloor Spreading
Seafloor spreading is the process by which new oceanic lithosphere is generated at divergent plate boundaries. Magma rises from the mantle, cools, and solidifies to form new crust on both sides of a mid-ocean ridge. This process provides evidence for plate tectonics through magnetic striping patterns in ocean floor rocks.
Real World
Harry Hess discovered in the 1960s that rocks on the Atlantic Ocean floor showed symmetrical magnetic stripe patterns either side of the Mid-Atlantic Ridge, proving that new crust was being created and pushed outward.
Exam Focus
Name specific evidence types — magnetic striping, radiometric dating, sediment thickness — to access full marks on evidence questions.
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