1. Continental-Continental
Type
Direction of
motion
Constructive or Destructive?
Description: Results of this plate action
Tectonic plates are sliding past one another
Earthquakes
Ex: San Andres fault in CA-Pacific Plate sliding past N. American Plate
Transform
boundary
Two tectonic plates are moving apart
A mid-ocean ridge forms
Ex: Mid-Atlantic Ridge- N. American/Eurasian plates diverging and S. American/African plates diverging
Divergent
Boundary:
Oceanic-Oceanic
Two plates moving apart
rift valley forms
As rift widens and drops the sea could eventually fill in over the land
Ex: Great African Rift Valley in East Africa
Divergent
Boundary:
Continental-Continental

2. Constructive or Destructive?
Type
Direction of
motion
Description: Results of this plate action
Constructive or Destructive?
Two oceanic plates come together & collide. The MORE dense plate will sink (subduct) under the less dense plate
Ocean trenches form, island arcs form from the building of under water volcanoes, earthquakes can occur
Examples:
Japan (Phillipine/Pacific/Eurasian plates)
Marianas Trench
Aleutian Islands (N. American/Pacific Plates)
Convergent
Boundary:
Oceanic-Oceanic

3. Constructive or Destructive?
Type
Direction of
motion
Description: Results of this plate action
Constructive or Destructive?
An oceanic plate and a continental plate collide. The more dense oceanic crust subducts under the continental crust. Rock that subducts into the hot mantle melts back into magma.
Ocean trenches form at subduction zone
Volcanic mountains on the continental side
Example:
1) Andes Mountains (Nazca Plate subducting under the S. American Plate)
2) Cascade Mountains in WA & OR (Juan de Fuca Plate is subducting under the N. American Plate) **Mt. St. Helens Volcano**
Convergent
Boundary:
Continental-Oceanic
SUBDUCTION ZONE

4. Continental-Continental
Type
Direction of
motion
Description: Results of this plate action
Constructive or Destructive?
Two continental plates come together & collide. Neither is dense enough to sink so the collision squeezes the crust until it is forced upward.
Folded mountains form
Ex: Himalayan Mountains (Indian and Eurasian plates colliding)
Convergent
Boundary:
Continental-Continental