Warm-Up January 21 Write What You Know! Write everything you know about the prompt below for five minutes, try for at least 3-4 complete sentences. On the ocean floors, where do you find older oceanic crust, and where do you find newer oceanic crust?

Sea-Floor Spreading Notes (Chapter 1.4)

Sea-Floor Spreading Mid-Ocean Ridge: A landform found at oceanic divergent boundaries An underwater chain of mountains A place deep on the ocean floor that flourishes with bizarre life

Sea-Floor Spreading Sea-Floor Spreading: The sea-floor spreads apart along a mid-ocean ridge as new crust is added Ocean floors move like conveyor belts, pushing the continents along with them

Sea-Floor Spreading Evidence from Molten Material Scientists have visited the mid-ocean ridge and observed rocks that form when lava cools rapidly underwater Evidence from Drilling Samples Drill samples show that rocks furthest away from mid-ocean ridge are older (rocks along the coasts), and rocks along the mid-ocean ridge are younger

Sea-Floor Spreading Evidence from Magnetic Stripes Earth’s magnetic poles switch over millions of years Ocean floor rocks contain iron, which orients to the “North” pole when cooling from lava, forming magnetic stripes along the ocean floor

Sea-Floor Spreading Deep-Ocean Trenches Subduction A landform that occurs at ocean-continent convergent boundaries A deep underwater trench that forms when the oceanic crust is subducted back into the mantle underneath the continental crust Subduction When oceanic crust sinks, melts, and is recycled back into the mantle