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. Divergent
2. Convergent
3. 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. Subduction
2. 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 volcanoes
 Generates 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/anima
tions/ch2.htm
 http://www.classzone.com/books/earth_science/ter
c/content/visualizations/es0804/es0804page01.cfm
?chapter_no=08