The Earth has 4 major layers  Crust  Mantle  Inner Core  Outer Core

The Crust 22 types of crust OOceanic (thin, very dense, made of basalt) CContinental (thick, less dense, made of granite)

Oceanic and Continental Crust

Convection in the Mantle  Magma in the mantle is heated by the core and rises to the surface (just below the crust).  Magma cools and sinks back to the core.  This creates movements we call “convection currents”

Plate Tectonics  The crust floats on top of the mantle.  Convection currents in the mantle move the plates around.  This makes the plate bump into each other in different ways

There are 3 Types of Plate Boundaries  Divergent  Convergent:  Ocean-Ocean  Ocean-Continent  Continent-Continent  Transform

Divergent Plate Boundaries  Divergent plates cause SEA FLOOR SPREADING.  Over geologic time, divergent faults cause continents to move away from one another.  Start off as Rift Valleys, eventually become Mid-Ocean Rifts

Convergent Boundaries  Convergent boundaries occur when two plates collide.  The lighter plate always goes over the heavier plate.  The heavier plate is SUBDUCTED  Create VOLCANOES (on land and in sea), and MOUNTAIN RANGES.  THERE ARE 3 TYPES OF CONVERGENT PLATES BOUNDARIES

Ocean-Continent Plate Boundaries  Occur when an oceanic and continental plate meet.  The ocean plate is heavier and slides under the continent.  Often results in volcanoes on land and mountain ranges

Continent-Continent Plate Boundaries  Occur when continental plates meet.  Both are heavy and neither can be pushed down into the Earth.  Can either smush together, or one can go on top of the other, resulting in very tall mountains.  Eventually, they come to a stop. Himalayan Mtns. p0IE

Ocean-Ocean Plate Boundaries  Occur when two oceanic plates meet. They are both heavy, and one sea floor slides over another.  A trench is formed, and often chains of islands result. wpI&feature=related

Hot Spots vs. Convergent Boundaries  Both hot spots and ocean- ocean convergent boundaries can create chains of islands.  However, convergent boundaries create islands when one plate is subducted another. Islands creates this way are usually bigger.  Hot spots are bubbles of magma that create islands as a plate moves above it.

Transform Plate Boundaries  Occur when two plates slide past each other.  Create Strike-slip faults, can create hills, but not mountains.  San Andreas Fault