Download Plate Tectonics – study of crustal movement, and the

Plate Tectonics – study of crustal movement, and the results of that movement.
Lithosphere – outer layer
of the earth (60 – 150
miles deep over
continents, 3 – 50 miles
deep over oceans),
consisting of the crust
and outer mantle.
Exhibits rigid behavior.
Asthenosphere – partially
melted rock that is soft,
and can flow, not rigid.
The lithosphere floats on the asthenosphere like an iceberg floats on water. The
thicker the crust, the higher the elevation of the crust.
Continental Crust consists predominantly of
feldspar and quartz, with density of 3.0
g/cm3. Averages 20 miles thick
Oceanic Crust consists mainly of FeMags,
with a density of 3.2 g/cm3. Averages 3
miles thick.
Lower density of continental crust causes it
to float higher on the asthenosphere than
oceanic crust.
Through nuclear reactions occurring in the
core, heat is generated, and causes the
asthenosphere to convect. This causes the
lithosphere to move like it were on a
conveyer belt.
The Earths crust is composed of 7 large, rigid plates, and many smaller plates.
Between each plate is 1 of 6 types of boundaries:
Diverging Plate Boundaries:
1) Diverging Ocean : Ocean
mid-Atlantic is a good example.
As plates move away from the mid-ocean
ridge, fractures are filled with molten rock
from the mantle. Cooling then creates
brand new crust. The further you move
away from the ridge, the older the ocean
crust.
2) Diverging Continent : Continent
Example: Africa and Saudi Arabia
This is what started the
separation of Europe from
North America.
Ocean crust is more dense than continental crust,
therefore subducts (goes under) continental crust,
Converging Plate Boundaries:
and is then melted back into the mantle, to be
recycled as new ocean crust later in time. Creates
3) Continental : Oceanic
mountain ranges above subduction zone.
Example: Cascades (Washington to California) and Andes (South America)
4) Converging Ocean : Ocean - Creates a chain of islands, (called an island arc)
as one ocean plate subducts below the other.
Japan is a chain of
islands formed by
subducting ocean
plates.
5) Converging Continental : Continental
Examples: India and Asia collision forms the Himalaya Mountains
6) Transform Boundary, where 2 plates don’t collide, but rather, slip past each
other.
A stationary “hot spot” of upwelling magma rises under the Pacific Ocean,
and as the Pacific crust passes over the hot spot, volcanoes form.
Features along plate boundaries:
1) Faults and Earthquakes
2) Volcanoes
3) Mountains
4) Trenches
5) Ridges