Plate Tectonics Earth’s Interior Pangaea Plate Movement Plate Boundaries.

Plate TectonicsPlate Tectonics

• Earth’s Interior• Pangaea

• Plate Movement• Plate Boundaries

PangaeaPangaea• Theory stating all of the continents were once joined

as a “super-continent”• Alfred Wegener proposed this idea • Looked at specific evidence (fossils/rock record/fit)

from one continent to the next.• Proposed all continents once fit together, then broke

apart. Hence the term, Continental Drift.

Plate MovementPlate Movement

• Plates move because the Asthenosphere– a layer of partially melted rock that is able to

flow (like silly putty) with the aid of convection currents (“heat currents”)

– Convection currents slowly move the ridged crust in a specific direction

– Movement per year is about the same as how long your fingernails grow per year (how much is that!?)

Plate MovementPlate Movement• When plates move, they collide with one

another’s boundaries. • Three main types of boundaries

-Convergent

-Divergent

-Transform

Plate BoundariesPlate Boundaries

• Type of Boundary

• Convergent– Oceanic-oceanic– Oceanic-continental– Continental-

continental

• Divergent

• Transform

• Result of Boundary• Plates come

together – Subduction zone/

volcanic islands– Subduction zone/

volcanic mountains– Non-volcanic

mountains

• Plates moving away from one another, creates new sea floor

• Plates sliding past one another, creates earthquakes

Convergent BoundariesConvergent Boundaries

• Oceanic-Oceanic Boundary

• Plates converge creating a subduction zone—one plate slides underneath the other plate creating a volcanic arc (volcanic islands)

• This will also create a trench in the ocean

Convergent BoundariesConvergent Boundaries

• Oceanic-Continental Boundary• Subduction zone—oceanic plate slides under

continental plate because it is more dense.• The oceanic plate breaks off and melts once it is

heated in the mantle. • The melted plate then comes through the

continental plate to create volcanoes on the continental plate

• Additionally, this will create an oceanic trench

Convergent BoundariesConvergent Boundaries• Continental-

Continental• When two continental

plates come together, the two plates “crumple” much like a piece of paper

• This creates huge mountain ranges, e.g. Himalayans & Mt. Everest

Divergent BoundariesDivergent Boundaries

• If two continental plates diverge, the continent would stretch much like a rubber band getting thinner and thinner with each stretch

Divergent BoundariesDivergent Boundaries

• Occur mainly on the sea floor between oceanic plates

• When the sea floor spreads, it splits, thus creating a way for the mantle to rise through the crust, creating new sea floor.

• Example: Mid-Atlantic Ridge.

Transform BoundaryTransform Boundary• Transform boundaries slide past one

another laterally• Can slide uniformly or they can get

“stuck” at a particular point until there is enough pressure to move past the “stuck” point

• When there is enough pressure to move beyond this point, we may feel the movement as an earthquake depending on the intensity

• An example of a transform boundary is the San Andres Fault in California

Hot SpotsHot Spots• There are several volcanoes caused by “hot spots”

• A hot spot is a point in the mantle where a plume of hot material rises to the surface causing an area of geo-thermal activity.

• Hot spot does not move, the plate does • ExamplesExamples of hot spots include: the Hawaiian

Island Chain and Yellowstone National Park• One theory indicates hot spots as the reason for the break up of Pangaea