9.3 & 4: Theory of Plate Tectonics

lithosphere forms the thin outer shell of Earth and is broken into several pieces called plates asthenosphere: solid, plastic layer of the mantle beneath the lithosphere made of mantle rock that flows very slowly which allows plates to move on top of it

plate tectonics: theory that explains how large pieces of the lithosphere (plates) move and change shape plates ride on the asthenosphere like blocks of wood float on water continents and oceans are carried along on the moving plates like passengers are carried by a bus

plates can include continental crust, oceanic crust, or both

scientists have identified about 15 major plates boundaries of the plates do not always match the outlines of continents

plate boundaries may be in the middle of the ocean floor, around the edges or within continents three types of plate boundaries are divergent, convergent, & transform fault each plate boundary has a characteristic type of geologic activity

divergent: where plates move apart area where new crust forms Chapter 10 divergent: where plates move apart area where new crust forms usually found on the ocean floor can also create volcanoes

convergent: where plates run into one another (come together) Chapter 10 convergent: where plates run into one another (come together) three types of convergent boundaries based upon types of plates that are colliding 10

Chapter 10 ocean/continental = ocean crust (is denser) is pushed down into the mantle, creating a trench

can also make a range of volcanic mountains called a continental volcanic arc due to melting of the ocean plate in the mantle

ocean/ocean = one is pushed down into the mantle creating a trench Chapter 10 ocean/ocean = one is pushed down into the mantle creating a trench 13

can also make a range of volcanic mountains that are in the ocean so are called a volcanic island arc

continental/continental = both are pushed up creating a mountain range Chapter 10 continental/continental = both are pushed up creating a mountain range 15

transform fault: plates grind past each other causes earthquakes Chapter 10

How Does This Happen? convention currents in the mantle are the driving force behind plate movements