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