The Theory of Plate Tectonics

Theory of Plate Tectonics 1.Continents appear to “drift” with time 2.Lithosphere is broken up into rigid “plates”, that are moving 3.There are three types of plate boundaries: 1.Divergent 2.Convergent 3.Transform

3 types of plate boundaries: 1.Divergent – such as a mid ocean ridge where sea floor spreading occurs 2. Transform boundary – where 2 plates slide along side of one another 3. Convergent – where 2 plates collide

A transform plate boundary

Transform plate boundary

Transform Boundary in California

Close up of San Andreas Fault

Transform boundaries also exist at offsets along the mid ocean ridge

There are 3 types of convergent plate boundaries 1. Ocean plate and another ocean plate 2. Ocean plate and a continental plate 3. Continental plate and another continental plate Example: the Aleutian trench Example: Peru-Chile Trench Himalayan Mountains

2 oceanic plates collide

Oceanic plate and a continental plate collide

Ocean-continent convergent plate boundary

Subduction is forming the Andes Mountains Convergent Plate Boundary Ocean plate and continental plate

Two continental Plates collide

Continent- continent convergent plate boundary

India colliding with Asia

Name this plate boundary Continental crust Mantle The oceanic crust melts and rises Explosive volcanoes Oceanic plateThe oceanic crust sinks under the less dense continental crust Match the labels to the letters A B C D E F

Hot Spot

Yellowstone National Park Another Hot Spot

In Summary: 1. The Earth’s surface is broken up into plates 2. The plates move a few centimeters per year in different directions 3. The plate boundaries may be classified into convergent or divergent or transform 4. Divergent plate boundaries are rift zones usually associated with a mid ocean ridge

Convergent Plate Boundaries may be the following types 1.Two oceanic plates- resulting in a subduction zone and an island arc. Ex. Aleutian Islands and trench 2. An oceanic plate and a continental plate – resulting in a subduction zone and coastal mountains – ex. Andes Mtns. 3. Two continental plates – resulting in severe uplifting of the earth’s crust and a very large mountains like the Himalayas, or the Alps