Transcript Ch 2 - Plate Tectonics

CHAPTER 2, SECTION 1
 The lithosphere is broken into separate sections
called plates.
 The geological theory that states that pieces of
Earth’s lithosphere are in constant, slow
motion, driven by convection currents in the
mantle is plate tectonics.
Continental Drift
Continental drift is the
theory that the plates
slowly move, and the
continents slowly
move as a result.
 http://www.nature.nps.gov/geology/usgsnps/anima
te/A06.gif
Types of plate boundaries:
 1.) convergent—where one plate sinks beneath
another.


Oceanic crust is denser and is subducted underneath the
continental plate.
If both plates are continental or oceanic, the larger plate will be
subducted.
 2.) divergent—Where plates move away from each
other. This occurs near weak spots in the plate
caused by rising magma currents.
 3.) transform—where two lithospheric plates slide
past each other.
Divergent Plate
Boundary
A rift valley is where the crust stretches until it
breaks. An example is the Great Rift Valley in
eastern Africa.
Divergent Plate Boundary: Mid-ocean ridge
 Underwater mountain
system that is formed by
plate tectonics.
 Oceanic crust spreads
allowing magma to reach
the surface and create
new ocean floor.
 http://www.nature.nps.g
ov/geology/usgsnps/ani
mate/A48.gif
Convergent Boundary
 A trench forms where
two plates collide
(subduction occurs)
on the ocean floor.
The plate that is
subducted will then
melt and once again
become magma.
Mt. Everest-Highest point
(29,028 feet)
India and Asia collided about 55 million years
ago
Mariana Trench – Lowest point (35,800 feet)
A fold is when the squeezing of the continental plates
leads to rocks that have been compressed into bends.
An example is the Appalachian Mountains.
Transform
Boundary
Faults are places where rock masses have
broken apart and moved away from each
other.
Pacific Ring of Fire—25,000 miles—75% of
the world’s volcanoes and 90%of the world’s
earthquakes
The story of a rock…
Weathering is the breakdown of the materials of
rocks into smaller pieces. These smaller
particles of gravel, sand, and mud are called
sediment.
Water causes weathering
What evidence of
weathering do you see in
this picture?
Wind causes weathering
What evidence of
weathering do you see in
this picture?
Ice causes weathering
Describe how ice causes
weathering.
Erosion
The process by which water, ice, wind or gravity
moves fragments of rock and soil.
What evidence of erosion
do you see in this picture?
Erosion is Movement of Sediment
Erosion carves the
Earth's surface creating
canyons, gorges, and
even beaches.
What do you think has caused this
rock to look this way?
The energy-rich substances
formed from the remains of
once living organisms (decayed
plant and animal remains from
long ago).
The 3 major fossil fuels -->
Coal, Oil, and Natural gas.