plate tectonics objective(s): swbat describe the layers of the earth. swbat describe the plate...

Plate TectonicsObjective(s): SWBAT describe the layers of the Earth.

SWBAT describe the plate tectonics theory including, how plate tectonics operating over geologic time has changed the patterns of land, sea, and mountains on Earth’s surface.

SWBAT differentiate between the features of the three different kinds of plate boundaries.

HA HA HA

Structure of the Earth

http://www.youtube.com/watch?v=Q9j1xGaxYzY

Structure of the Earth

GPS (Global Positioning System) – 24 satellites orbiting the Earth at a height of 20,200 km.

Divergent Plate Boundary: Sea Floor Spreading

When two plates move away from each other.

Divergent Plate Boundaries:Sea Floor Spreading

Divergent Plate Boundaries Most found on the seafloor where they form

mid-ocean ridges. (two plates moving away from one another)

New crust forms at mid-ocean ridges, thus younger rock is closer to the spreading center.

Sea-floor spreading: mantle asthenosphere (top part of mantle) slowly rises upward as magma (molten rock). Magma rising up is less dense than the surrounding rock and forms volcanoes in the central valley of the mid-ocean ridge.

Divergent Plate Boundary:Mid-Atlantic Ridge

Divergent Plate Boundary:Mid-Atlantic Ridge - Iceland

Divergent Plate Boundary: Rift Valley

Divergent Plate Boundaries: Rift Valley

Rift Valley: a large, long valley on a continent, formed where the continent is pulled apart by forces produced when mantle material rises up beneath the continent.

They can occur in both continental and oceanic plates.

Divergent Plate Boundary:East African Rift Valley

Convergent Plate BoundaryTwo lithospheric plates move toward each other.

Convergent Plate BoundaryWhen Continental plates move toward each other.

A look at the big picture

A Map of the Major Plates of the World

A World View of Boundary Types

Key: 1. Divergent plate boundaries 2. Transform plate boundaries 3. Convergent plate boundaries 4. Plate boundary zones 5. Selected prominent hotspots

A Closer Look at the West Coast

Convergent Plate Boundaries

(two plates moving toward one another)

3 types of convergent plate boundaries Subduction – the movement of one plate downward

into the mantle beneath the edge of the other plate at a convergent plate boundary. The downgoing plate is always oceanic lithosphere. The plate that stays at the surface may be either ocean lithosphere or continental lithosphere.

*Old crust is recycled at subduction zones

Convergent Plate Boundaries1. Oceanic-Oceanic: One plate has become denser

than the other as a result of cooling. The process of subduction creates a deep-sea trench. As one plate goes down into the mantle asthenospehere, magama is produced at a certain depth. The magma rises up to the ocean floor to form a chain of volcanic islands (volcanic island arc)

Convergent Plate Boundary

Oceanic-Oceanic Convergent Boundary

Convergent Plate Boundaries2. Oceanic-Continental: The oceanic plate subducts

beneath the continental plate. This forms a trench and a volcanic arc along the edge of the continental plate. (mountain ranges composed of many volcanoes)

Convergent Plate Boundary

Oceanic-Continental-

Example: Andes Mountains

Convergent Plate Boundaries3. Continental-Continental: The colliding edges of the

continents are crumpled and uplifted to form a mountain range.

Suture Zone: the zone on the Earth’s surface where two continents have collided and have been

welded together to form a single continent.

Convergent Plate Boundaries: Continental-Continental: Himalyans

Transform Plate Boundaries

Two plates slide parallel to each other

Transform Plate Boundaries (plates slide horizontally past one another) Crust is deformed or fractured, not formed or

recycled

Characterized by long faults and shallow earthquakes

Many transform boundaries off-set mid-ocean ridges

Transform boundaries on continents is rare

Example: San Andreas Fault (several hundred kilometers long)

Transform Boundary on Land