Plate Tectonics

Terminology The term “plate” refers to the subdivision of the earth’s crust and lithosphere. The term “tectonics” refers to the deformation of the earth’s crust. “Plate tectonics” refers to the formation and migration of these plates. Subduction zone is where two plates come together, and one is forced below the other.

It is puzzling! Alfred Wegener developed a theory that states that all present continents were once together and collectively known as a 'supercontinent' called a Pangaea. The Pangaea theory was treated with much skepticism when it was first raised. But since then, there have been much evidence to support this theory.

There are 3 types of boundaries: Divergent plate boundaries Convergent plate boundaries Transform plate boundaries

Divergent plate boundaries Divergent plate boundaries are where two plates move apart or separate Magma is heated by convection, rises and pushes the plates apart This creates a new sea floor Also called seafloor spreading

Rifts and Ridges Great Rift Valley in Africa Mid-Atlantic Ridge Back to boundary types

Convergent Boundaries This is where two plates come together One plate is forced to sink below the other Subduction zone There are three types of convergent boundaries: Ocean-continent Ocean-ocean Continent-continent Back to types of boundaries

Back to convergent boundaries Oceanic-continental The subduction zone is where the oceanic plate is forced below the continental plate. A deep trench is formed off shore A mountain range is formed on land An example is the West coast of North America Back to convergent boundaries

Back to convergent boundaries Oceanic-Oceanic Where two oceanic plates converge A deep ocean trench is formed A island chain of volcanoes is formed Examples would be Hawaii or Japan Back to convergent boundaries

Continent-Continent Where two continental plates come together The plates push together to form a chain of high, jagged mountains Examples would be The Himalayas back

Transformation boundaries This occurs between two plates that scrape against each other At this type of boundary, a fault is created A common result is an earthquake A very well known example is the San Andreas Fault in California

Now, let’s review!

1) At a divergent plate boundary, how do plates move? a) Grind past each other b) Collide with each other c) Rift apart d) Move under each other

2) Oceanic trenches are formed by: a) Sea-floor spreading b) The collision of continents c) The subduction of oceanic crusts into the earth’s mantle d) The subduction of continental crust into the earth’s mantle

3) The supercontinent composed of all of the continents proposed by Alfred Wegener is called: a) Mantle b) Pacific c) Pangaea d) Plate tectonics

4) Where would an earthquake happen? a) At a divergent plate boundary b) At a convergent plate boundary c) At a transform plate boundary

5) What is not a result of plate tectonics? a) Hurricanes b) Volcanoes c) Earthquakes d) Mountains

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