Download Chapter 9: Plate Tectonics Review

Plate Tectonics
Review
Layers of the Earth
From the Earth’s Crust to the Inner Core:
Depth Increases
Pressure Increases
Temperature Increases
Layers
of the
Earth
Temp.
(°C)
Elements
Crust
0- 860
Oxygen,
silicon
Mantle 870
Iron,
magnesium
Outer
Core
2200
Iron, nickel
Inner
Core
5000
iron
Lithosphere
• The cool, rigid layer of the crust and
upper most solid mantle.
• This layer is broken down into several
large tectonic plates.
Asthenosphere
• The asthenosphere is the semirigid part of the middle mantle
that flows like hot asphalt
under a heavy weight.
• The tectonic plates float on
this semi-liquid layer.
Lithosphere vs. Asthenosphere
Lithosphere= rigid
Asthenosphere= semi-soft
Convection Currents in the Mantle
• According to scientists, convection currents is
the driving force behind the movement of the
Earth’s plates.
Convection
• Heated water is less dense therefore rises
while cooled water is more dense, which
sinks.
• This is also true with air and other fluids.
Alfred Wegener’s hypothesis on
Continental Drift
All the continents had once been
joined in a single landmass,
called Pangaea, and have since
drifted apart.
• Evidence from Landform
• Evidence from Fossils
• Evidence from Climate
Evidence of Continental Drift
 A mountain range lines up between Argentina in South America and
Africa.
 Fossils of the reptiles Mesosaurus and Lystrosaurus have been found in
places now separated by oceans.
 Fossils of the fernlike plant, Glossopteris, have been found in rocks in
Africa, South America, Australia, India, & Antarctica.
 Deep scratches in rocks show that continental glaciers once covered South
Africa.
Pangaea
• A supercontinent, meaning “all lands”, that
existed about 300 million years ago.
Sea-Floor Spreading
Theory
As the plates diverge, molten material rises from
the mantle and erupts along the mid-ocean
ridge.
Image: A diver swims between
the Eurasian and North
American plates in Thingvellir
lake, Thingvellir National Park,
Iceland. Iceland is one place
where a mid-ocean ridge can
be seen on land and in shallow
waters.(credit: Wild Wonders
of Europe/Lundgre
http://www.bbc.co.uk/science/earth/surface_and_interior/mid_ocean_ridge
Plate Tectonics Theory
• Geological theory that states that pieces of
Earth's lithosphere are in constant, slow
motion
Divergent Boundaries
• Plate boundary where 2 plates move away
from each other.
• Is the result of new ocean floor, such as the
mid-ocean ridge and rift valley’s on land.
Convergent Boundaries
• Two plates move towards each other and collide.
• The result can be an ocean trench, volcanic island
arc, volcanoes, and folded mountains.
Cause of Deep Ocean Trenches
• When an ocean plate collides with a continental
plate, the plate is subducted under the continent.
• Subduction – when one tectonic plate (oceanic) is
pushed underneath another tectonic plate.
Folded Mountains
• When 2 continental plates collide, folding
mountains occur
Himalayans from space
Transform Boundaries
• Plate boundary where two plates slip past
each other, moving in opposite directions.
• Earthquakes frequently occur along these
boundaries.
• Creates a fault
Earthquakes
• Occur usually when 2 plates slide past each
other, however, can happen at all plate
boundaries.
• Release of energy when the lithosphere
suddenly breaks and slides
Ring of Fire
Volcanoes form where tectonic plates meet
other plates.