Transcript Plate Tectonics

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
DRIFTING CONTINENTS
DRIFTING CONTINENTS
Two Types of crust
• Continental Crustmade 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, midAtlantic 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