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 Trench Volcanic arc

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 Aulacogen Active Rift Mantle Plume