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EARTH SCIENCE JOURNAL DATE: • Examine the diagram above. Describe the movement of the plates and the processes that are occurring. • What type of plate boundary is this? Mechanisms of Plate Motion • MANTLE CONVECTION CURRENTS • Mantle rock is so warm that it churns slowly around like very very thick syrup boiling on the stove! Mechanisms of Plate Motion • MANTLE PLUMES AND HOT SPOTS • Hot spots are created by mantle plumes. • Mantle plumes are hot currents that rise all the way from the core through the mantle. • Mantle plumes can come up under the crust and burn their way through to create hot spot volcanoes. Mechanisms of Plate Motion • HOT SPOTS stay in the same place while tectonic plates move over them. • Each time the plate moves the hot spot creates a new volcano. (Hawaiian Islands) Hot Spots track plate movement! Click here to see this in motion Shifting Poles Paleomagnetism • The magnetic poles typically wander around slowly. • But every so often flip completely, reversing the magnetic polarity of the planet. More Evidence of Plate Tectonics • The experts are reasonably sure the earth's magnetic field is a result of movement in the planet's liquid iron and nickel core. • As the iron-rich magma pushing up from beneath the plate boundary cools and spreads out, the mineral crystals align themselves with the magnetic field as it then exists. • The alternating stripes indicate field flip-flops over geological time. The alternating stripes indicate field flipflops over geological time. Magnetic Reversals Record SeaFloor spreading