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
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 Boundary
• Plates move away
from each other
• Forms volcanoes,
new crust and rift
valleys
• Ex) Iceland, midAtlantic ridge
Divergent Boundary –
Arabian and African Plates
Divergent Boundary –
Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Rift Valleys
• A deep valley formed
as plates move apart
at a divergent
boundary.
• Ex) The Great Rift
Valley in eastern
Africa
Sea Floor Spreading
• Mid Ocean Ridges – underwater mountain
chains that run through the Earth’s Basins
• Magma rises to the surface and solidifies
and new crust forms
• Older Crust is pushed
farther away from the ridge
Transform Boundary
• Plates slide past each
other
• Creates earthquakes
• Ex) San Andreas
Fault in California
Convergent Boundary
• Plates move toward
each other
• Earthquakes, forms
mountain ranges
• Ex) Himalayan
Mountains
Continental-Continental Boundary
• Plates fold, creating mountains
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Oceanic-Oceanic Boundary
•
•
•
•
Creates trenches (deep valleys)
Forms volcanoes
Forms Island Arcs
Ex) Aleutian Islands (Alaska)
Convergent Boundary – Oceanic & Oceanic
Subduction occurs when the denser plate sinks below the
other
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Oceanic-Continental Boundary
• Oceanic plate pushes
down because it is
more dense.
• Creates deep ocean
trenches
• Creates coastal
mountain ranges
• Ex) Andes mountains
Convergent Boundary – Oceanic & Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Hot Spots
• Hot material rises
from deep within the
mantle.
• Heats the lithosphere,
causing volcanoes at
the surface.
• Ex) Hawaiian Islands,
Yellowstone N.P.
Evidence of Pangaea
Vocab to Remember
• Fault
• Convection
• Divergent Boundary
• Convergent Boundary
Vocab ctd…
• Transform Boundary
• Rift Valley
• Hot Spot