Download Chapter 4: Plate Tectonics

Chapter 4: Plate Tectonics
PowerPoint Review
Section 4.1 Earth’s Interior
Can you name Earth’s layers?
The crust
The mantle
The outer core
The inner core
The Crust
Crust - a layer of rock
that forms Earth’s
outer skin
2 Types of Crust
 continental crust -the
crust that forms the
continents (granite)
 This includes both dry
 oceanic crust-the crust
land and ocean floor
beneath the ocean
(basalt)
The Mantle
The mantle is made of three parts:
1. Lithosphere - uppermost part of the mantle (rigid,
hard layer)
2. Asthenosphere - some what soft and can bend like
plastic
3. Lower mantle - solid layer beneath the
asthenosphere
The Core
Outer Core
 Molten metal made of
iron and nickel
 The movement of the
outer core creates
Earth’s magnetic field.
Inner Core
 A dense ball of solid
material made of iron
and nickel
Travel to Earth’s
Interior…Impossible
Heat
Pressure
Temperature
increases 1° C for
every 40 meters
traveled
Pressure increases
as you move deeper
into Earth’s interior
How Do We Know What’s Inside?
Evidence from rock samples
– Drilling samples
– Volcanic eruptions blast rock to the surface
Evidence from seismic waves
– Geologists study how they travel through Earth
Layers of the Earth
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Section 4.2 Convection in the
Mantle
There are three types of
heat transfer: radiation,
conduction and
convection.
Radiation
Radiation- the transfer of
energy through space
 No direct contact with
the heat source
 Sunlight
Conduction
Conduction- heat transfer within a material or between
materials that are touching
 A metal spoon heats up in a pot of boiling water
Convection
Convection - heat transfer by movement within a fluid
Let’s take a look at heat transfer.
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Section 4.3 Drifting Continents
Alfred Wegener
 Wegener’s hypothesis was that all the continents
were once joined in a single landmass and have since
drifted apart.
 Wegener’s evidence to support continental drift
included the puzzle-like fit of the continents, similar
mountain ranges, glacial deposits, coal belts,
Glossopteris fossils as well as fossils from
Mesosaurus and Lystrosaurus.
A Theory Rejected
Since Wegener couldn’t explain the force that
would move massive continents, his theory
wasn’t accepted by the scientific community
until after his death.
Section 4.4 Sea-Floor Spreading
Old Sea-Floor
New Sea-Floor
Mid-Ocean Ridge
Mid-ocean ridge - an undersea
mountain chain that is part
of a long system of
mountains that winds
beneath Earth’s oceans.
 The ocean floor is mapped
using sonar.
Sea-Floor Spreading
Evidence of Sea-Floor
Spreading
 Molten material
 Magnetic stripes
 Drilling samples
How Subduction Happens
Convection currents pull the ocean floor
apart at mid-ocean ridges
Magma rises and cools creating new sea-floor.
Gravity pulls old, dense sea-floor down
beneath the trench.
Old sea-floor is recycled back into the
mantle.
Takes 200 million years!
Let’s see it in action.
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Section 4.5 The Theory of Plate
Tectonics
Plate Boundaries
There are three kinds of plate
boundaries: spreading boundaries,
colliding boundaries, and sliding
boundaries.
Spreading Boundaries
 AKA: divergent
boundary
 Two plates move apart
 Ocean: mid-ocean
ridge
 Land: rift valley
Most common type of
boundary
Colliding Boundary
 AKA: convergent
boundary
 Occurs where two
plates collide
Three Types
oceanic/oceanic
oceanic/continental
continental/continental
The Himalayas
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Sliding Boundary
 AKA: transform
boundary
 Occurs where two
plates move past each
other in opposite
directions
 Crust is neither created
nor destroyed
 San Andreas Fault
The End.