Plate Tectonics

The Earth’s Crust is Made of Plates

What Causes the Plates to Move? Convection- hot magma rises, cool magma sinks (like a lava lamp)

Convection Currents Hot magma in the Earth moves toward the surface, cools, then sinks again. Creates convection currents beneath the plates that cause the plates to move.

DRIFTING CONTINENTS 1. Theory of Continental Drift – Alfred Wegener’s theory that all continents were once one landmass called Pangea (theory proposed in 1910)

DRIFTING CONTINENTS

Two Types of crust Continental Crust- made of granite (light) Oceanic Crust- made of basalt (heavy)

Plate Boundaries Cracks in the plates are called faults

Types of Boundaries (Faults) Convergent Boundary Divergent Boundary Transform Boundary

Divergent Fault Plates move away from each other Forms volcanoes and new crust Ex) Iceland, mid- Atlantic ridge

Transform Fault Plates slide past each other (shearing) Creates earthquakes Ex) San Andreas Fault in California

Convergent Fault Plates move toward each other Earthquakes, forms mountain ranges & trenches Ex) Himalayan Mountains

Continental-Continental Convergent Boundary Plates fold, create folded mountains

Oceanic-Oceanic Convergent Boundary Creates trenches (deep valleys) Forms volcanoes Ex) Aleutian Islands (Alaska)

Oceanic-Continental Convergent Boundary Oceanic plate pushes down because it is more dense (subduction) Creates mountain ranges; Ex) Andes mountains