Transcript Plate Tectonics

Plate Tectonics
Theory of Plate Tectonics
Earth’s crust and
part of the upper
mantle are
broken into
sections
Sections of
Earth’s crust =
PLATES
Lithosphere
Rigid layer of earth, made up of
the crust and a part of the upper
mantle
Asthenosphere
Plasticlike layer below the lithosphere
where plates float and move around
Plate Boundaries
1. DIVERGENT
BOUNDARIES
2. CONVERGENT
BOUNDARIES
3. TRANSFORM
BOUNDARIES
Divergent Boundary
 The boundary
between two plates
that are moving apart
 TENSION- force that
pulls the plates
Features caused by divergent boundaries:
Rift valleys and mid-ocean ridges
Convergent Boundary
 When two plates
collide (move towards
each other)
 COMPRESSION-
force that pushes the
plates.
Features caused by convergent boundaries:
Mountains and earthquakes
Subduction Zone
 When an oceanic
plate converges with a
less dense continental
plate, the denser
oceanic plate sinks
under the continental
plate
Features caused by subduction zones:
Volcanoes
Transform Boundary
 When two plates
slide past one
another (plates move
in opposite
directions)
 SHEARING- force in
transform boundary
eatures caused by transform boundaries:
Earthquakes, faults
Types of Faults
Normal fault = the rock layers above the fault
move down when compared with rock layers
below the fault
Reverse fault = the rock layers above the fault
surface move up relative to the rock layers
below the fault
Strike-slip fault = rocks on opposite sides of
the fault move in opposite directions, or in the
same direction at different rates
Cause of Plate Tectonics
 Convection (heat) =
causes the movements
of plates
 Convection current:
cycle of heating,
rising, cooling, and
sinking
Testing for Plate Tectonics
Problem: Studying magnetic
characteristics of rocks, volcanoes
and earthquakes supported the
theory but did not provide PROOF.
Solution: New methods discovered
to measure amounts of plate
movement = satellites and lasers