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Cuernos Del Paine, Andes Mountains
Gabriel Callaghan
Examples of divergent boundaries
So, we’re making new crust?
Convergent plate boundaries
2 types of crust = 3 possible combinations
1. Oceanic lithosphere meets oceanic
lithosphere
2. Oceanic lithosphere meets continental
lithosphere
3. Continental lithosphere meets
continental lithosphere
Convergent boundaries involving
oceanic lithosphere
• At convergent boundaries oceanic plates are
subducted.
• Subduction is the recycling of oceanic crust into
the mantle
Play convection animation
Subduction zones are characterized by two things:
1. Deep trench
2. Long chain of volcanoes
Volcanic arc
Trench
Where is this
subduction zone?
• At oceanic-oceanic convergent boundaries,
volcanoes form chains of islands called island
arcs.
The Aleutian Islands in Alaska
• At continental-oceanic convergent boundaries,
volcanoes form long mountain chains such as
the Cascade Mountains.
Mt. Saint
Helens
• Subduction zones cause the largest
Earthquakes known.
• The 2004 Tsunami in the Indian Ocean was
caused by an earthquake at a subduction zone.
Continent-continent convergent
boundaries
• Neither lithospheric plate can be fully subducted.
• Instead, the plates pile up to form huge
mountain ranges
Where is this
continent-continent
collision?
You are
here
Play plate motions animation
Transform plate boundaries
• Relatively few volcanoes
• Lots of earthquakes, though not so large as at
subduction zones
Where is this
transform
boundary?
Mid-ocean ridge transforms
Hot Spots
Hot Spots of the World
Divergent boundaries
• Begin with rifting—upwelling of hot mantle
starts to break the crust apart
• Faults form rift valleys
• Decompression causes melting and volcanism
• New oceanic crust begins to form. The plate
boundary is now a mid-ocean ridge.
The Theory of Plate Tectonics
Active Rift
Aulacogen
Mantle Plume