Plate Boundaries

Plate Boundaries

Why do we care about plate boundaries?

Plate Boundaries

Volcanoes and earthquakes most often occur where tectonic plates come together.

At plate boundaries, many other geologic features, such as mountains and rift valleys, can also occur.

Plate Boundaries

There are three basic types of plate boundaries:

1. Divergent2. Convergent3. Transform Fault Boundary

Divergent Boundary

A divergent boundary occurs where two plates move apart and create a gap between them.

Divergent Boundary

Hot rock rises from asthenosphere and cools to form new lithospheric rock.

Diverging plates then pull newly formed lithosphere away from gap.

New lithospheric (oceanic crust) is formed.

Divergent Boundary

Mid-oceanic ridges are mountain ranges at divergent boundaries in oceanic crust.

Divergent Boundary

Real Life Example: Mid-Atlantic Ridge

Mid-Atlantic Ridge runs through Atlantic Ocean from Arctic Ocean to an area off the southern tip of South America.

Convergent Boundary

A convergent boundary occurs where two plates move toward one another.

Convergent Boundaries

There are two types of convergent boundaries:

1. Subduction2. Collision

Convergent Boundary - Subduction

Subduction is the process by which one lithospheric plate moves beneath another plate.

Convergent Boundary - Subduction

Ocean – Ocean

Two oceanic plates collide

Generates volcanoesGenerates island

chains

Real World Example Japan

Convergent Boundary - Subduction

Ocean – Continent

Oceanic and continental plate collide

A thin, dense oceanic plate collides with a relatively light, thick continental plate, the oceanic plate is forced under the continental plate

Real World Example Andes Mountains

Convergent Boundary - Collision

Continental – Continental

Two continental plates collide

Real World Example Himalayas

Transform Fault Boundary

A transform fault boundary occurs where two plates slide past one another.

Transform Fault Boundary

Plate movement at transform fault boundaries is one cause of earthquakes.

Real World Example San Andreas

Fault

http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=08