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Sci. 4-2 Restless Continents Pages 95-98 A.Continental Drift- a theory that continents can drift apart from one another and did so in the past 1)Alfred Wegener wrote this theory 2) evidence that supports continental drift a)The puzzle- like fit of the continents b)Fossils of the same species found on opposite sides of the ocean c)The pattern of grooves left by glaciers B. Pangaea- large supercontinent 1) broke into 2 pieces called Laurasia and Gondwana 2) Then broke into our current 7 continents C. Sea-Floor Spreading 1) Mid Ocean Ridges- a chain of underwater mountains in the Atlantic Ocean 2) Sea-Floor Spreading- the process by which new oceanic lithosphere is created as older material pulls away 3) spreading happens at the Mid Ocean Ridges 4) The newest crust is at the Ridge on both sides and the oldest is at the edges of the continents D. Magnetic Reversals- when Earth’s magnetic poles change place 1)This is evidence of sea-floor spreading 2) Molten rock comes up at the Mid Ocean Ridge. This molten rock has grains of magnetic minerals in it. 3) The grains of magnetic material acts like a compass pointing to the North Polarity. When the rocks cools, the grain is pointing in that direction permanently. 4) The changing polarity of the Earth’s magnetic poles causes the new oceanic crust to have alternating bands of normal and reverse polarity.