Plate TectonicsPlate Tectonics

Plate BoundariesPlate Boundaries

There are 3 main There are 3 main plate boundaries:plate boundaries:

1) Convergent 1) Convergent BoundaryBoundary

2) Divergent 2) Divergent BoundaryBoundary

3) Transform 3) Transform BoundaryBoundary

1. Convergent Boundaries1. Convergent Boundaries

Occurs when 2 Occurs when 2 plates plates collide.collide.

Oceanic plate is Oceanic plate is denser (3.2 g/cmdenser (3.2 g/cm33), ), faster and thinner - it faster and thinner - it is usually forced is usually forced under the under the continental plate continental plate (2.8 g/cm(2.8 g/cm33).).

The rock in the Oceanic plate melts as the The rock in the Oceanic plate melts as the plate sinks. The melted rock rises up plate sinks. The melted rock rises up causing volcanic eruptions.causing volcanic eruptions.

The area of convergence is called a The area of convergence is called a SUBDUCTION ZONE. SUBDUCTION ZONE.

When two continental plates collide:When two continental plates collide: They are the same density. They are the same density. This causes the plates to fold and bend This causes the plates to fold and bend

(mountain building) as well as earthquakes.(mountain building) as well as earthquakes.

Example of a Convergent Plate Example of a Convergent Plate BoundaryBoundary

South America: South America: Oceanic Nazca Plate is Oceanic Nazca Plate is

colliding into the South colliding into the South America plate. America plate.

Producing the Andes Producing the Andes Mountains (volcanoes Mountains (volcanoes along the mountain along the mountain crest) and formed a crest) and formed a deep trench off the deep trench off the coast in the Pacific coast in the Pacific Ocean. Ocean.

SUBDUCTION AT A PLATSUBDUCTION AT A PLATE BOUNDARYE BOUNDARY Animation Animation

Divergent Plate BoundariesDivergent Plate Boundaries Plates are being pulled apart Plates are being pulled apart

by convection currents in the by convection currents in the mantle.mantle.

As the plates separate along As the plates separate along the boundary, they crack into the boundary, they crack into faults and blocks. Magma faults and blocks. Magma from the mantle rises through from the mantle rises through the cracks. This cools and new the cracks. This cools and new crust is formed along the crust is formed along the boundary.boundary.

Earthquakes occur along the Earthquakes occur along the faults, and volcanoes form faults, and volcanoes form where the magma reaches the where the magma reaches the surface. surface.

Mid Atlantic RidgeMid Atlantic Ridge Mid-Atlantic Ridge is Mid-Atlantic Ridge is

a Divergent Plate a Divergent Plate Boundary.Boundary.

Over 15 000 km Over 15 000 km long.long.

Average height of Average height of volcanoes - 3 km.volcanoes - 3 km.

Sea-Floor SpreadingSea-Floor Spreading Animation.Animation.

Formation of OceaniFormation of Oceanic Crustc Crust Animation. Animation.

Example of a Divergent Plate BoundaryExample of a Divergent Plate Boundary

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The Process of RiftingThe Process of Rifting

Transform BoundaryTransform Boundary Places where plates slide Places where plates slide

past each other sideway.past each other sideway.

Transform boundaries are Transform boundaries are not marked by spectacular not marked by spectacular surface features, but their surface features, but their sliding motion causes lots of sliding motion causes lots of earthquakesearthquakes..

The slice of California to the The slice of California to the west of the fault is slowly west of the fault is slowly moving north relative to the moving north relative to the rest of California. rest of California.

The Problems of Haiti…The Problems of Haiti…

HOT SPOT VOLCANOES HOT SPOT VOLCANOES

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