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Introduction to Plate Tectonics Review • You have 5 minutes to draw an island from the side view. I will draw on the board a starting point for you and I would like you to finish the drawing. Islands actually look like….this! Review: Earth Layers • Crust, mantle, outer core, inner core • Made of rock: crust, mantle • Made of metal: both cores The Rock Layers • Crust: solid, hard rock • Very top of mantle: solid, hard rock • Rest of upper mantle: soft, gooey, hot rock Lithosphere & Asthenosphere • In order to describe the motion of tectonic plates, scientists divide the rock layers in a different way • Lithosphere: ALL of the solid, hard rock • (crust + very top of mantle) • Asthenosphere: The gooey, slightly melted rock • (rest of upper mantle) Lithosphere & Asthenosphere • So, the lithosphere is on top, and the asthenosphere is underneath • The lithosphere floats on top of the asthenosphere Lithosphere • Earth used to be completely molten • As it cooled, the lithosphere formed • BUT – the lithosphere cracked in several places (like a cracked eggshell) • So the lithosphere is actually made of several massive (huge) chunks called tectonic plates Lithosphere • There are 2 types of crust • Oceanic crust: the crust that holds the ocean • Very thin, very dense (heavy) rock • The newest rock - more is constantly being made • Continental crust – make Earth’s continents • Rock is much thicker and much older Asthenosphere • So, the chunks of tectonic plates float on top of the asthenosphere • The asthenosphere moves – how • Remember CONVECTION CURRENTS? • Heat from Earth’s core travels up through the asthenosphere, causing up and down movement Plate Movement • So convection currents make the asthenosphere move (it oozes and flows, like oatmeal) • This also moves the tectonic plates, which are floating on top of the asthenosphere