Download Forces that Shape the Earth State Objectives 4.a.

Forces that Shape the Earth
State Objectives 4.a.-4.b.
Structure of the Earth
The Earth is made of
__ layers.
 Inner Core, Outer Core, Mantle, Crust


core- Made of
and nickel
Temperatures at
°C (10,000°F)
due to great pressure from the above layers.


core- Molten (
) iron and nickel
Temperature between
°C (7,200°F) & 5000°C
Only _________________ Layer
- Thickest layer of Earth with hot ______ rock between the crust and the liquid
outer core.
 Regions of the mantle
o Uppermost mantle is solid, rocky, & brittle
 Upper/Middle is called the asthenosphere
 melts rocks, forming a substance called magma which flows like a thick
liquid
is the mechanically weak deforming region of the upper mantle
that is
&
due to extreme temperatures & pressure.

means that the consistency of the rock is flowing but it is not a liquid.
 Convection currents occur here due to ___________________ heating.
Convection Currents
Heat from the core and the mantle itself causes ____________ currents in the _______.
 Heating and cooling of the fluid, changes in the fluid’s
, and the force of
gravity combine to set convection currents in
.
- A solid layer of rock that includes both dry land and the ocean floor.
-The outermost shell of the rocky planet that floats on top of the
asthenosphere.
 Made up of the _______________ & the upper solid rocky part of the mantle
 ______________, rigid, & has fault lines
 Divided into plates

are large section of the earth’s crust and upper mantle that ride on
top of the asthenosphere.
Plate Tectonics
proposed two ideas that are known as
In 1912, German scientist Alfred
____________________ theory.
 Earth’s continents were once joined in a single large landmass called __________
that broke apart.
 Continents have drifted to their current location.

It has taken the continents about __________________ years since the breakup of
Pangaea to move to their present locations.
__________________________- claims that Earth’s plates are always in motion.
Plates move:
 slowly
 at different rates
 in different directions
Two Types of Lithospheric Plates
crust: made of rocks that are
and ride higher on
the mantle than oceanic crust.
crust: rocks that are
and ride lower on the mantle than
continental crust.
Plate Boundaries
Movement of Earth’s plates are responsible for most major geological events and
___________________ : Volcanoes, earthquakes, mountain formation
Plate
are where edges of plates _____________________.
Three Types of Plate Boundaries
1 Divergent Plate Boundaries
Boundaries
2 .Convergent Plate Boundaries
3. Transform Plate
plate boundaries form when two plates move away from each other.
Two Types: 2 oceanic & 2 Continental
2 Oceanic:
 Most occur on the ocean floor & form undersea mountain ranges called ________
.
 Magma wells up where plates pull apart creating new ocean crust in a process called
.
 Ex. Mid-Atlantic Ridge
 Create underwater volcanoes
Because of sea-floor spreading, the distance between Europe and North America is
increasing by a few centimeters per year.
Evidence for Sea-Floor Spreading
 Eruptions of molten material
 Magnetic stripes in the rock of the ocean floor
 Older rocks are located farther away from the ridge.
2 Continental:
 When two continental plates pull apart, a
 Ex: East African Rift
forms.

________________ occurs where there are breaks in the rock of the crust because
rocks slip past each other due to plate movements.
o
forces
Plate Boundaries: Boundaries that form when 2 plates collide or come
together

Forces (squeezing)
 ___________ is when earth’s crust is compressed causing it to bend & deform rocks
without breaking
Three Types
1. Oceanic & Continental
2. Two continental
3. Two oceanic
1. Oceanic and Continental
 The
oceanic plate is forced below the less dense continental plate
 Oceanic plate melts as it pushes into the mantle forcing hot magma & gas up to the
surface of the continent.
 Forms a deep-ocean trench & a long chain of continental ____________________.
 Ex. _________________ mountains of South America
 The movement of one plate under another is called ________________.
Volcanoes and Plate Boundaries
 Volcanic belts form along the boundaries of Earth’s plates.
 Hot spots called intra-plate regions
o These volcanoes are believed to have sources deeper down in the Earth's
mantle that remain in a relatively fixed location.
o Plates move over the ____________________
o Ex. The Hawaiian Islands
2. Two Continental Plates
 First, the ______________ between the continents is forced below one of the
continents
 Then, when the plates collide the continent crusts buckle, thicken, & rise up forming
______________ ranges.
 Ex. Himalaya & Appalachian Mountains
 _________________ occurs when compression forces bend rocks without breaking
them.
3. Two Oceanic Plates
 One plate is forced down into the mantle forming a deep ocean
that sinks &
melts.
 Magma & gas push through the ocean floor forming a chain of ________________.
 If a volcano becomes large enough, it rises above sea level & makes a volcanic
__________________.
 Ex. Japanese Islands, Philippines, Aleutian Islands
Transform Plate Boundaries: Two plates slide past each other without creating or
destroying the lithosphere.
 Form __________________ faults
 __________________ forces
 Earthquakes occur at transform boundaries.
 Ex: ___________________ Fault
 North American and Pacific plates slide past each other in a N – S direction creating
_________________________.
Earthquakes
_____________ are large cracks in the Earth’s crust where movement occurs.
 At strike-slip faults, rocks on either side of the fault are under pressure & can get
locked together.
 When too much pressure builds up, the rocks suddenly __________ past each other
releasing the pressure.
 The violent shaking of the Earth’s crust is known as an _____________________.
Seismic Waves
The _____________ is the place in Earth’s crust where the pressure was released.
____________ (earthquake) waves spread out in all directions from the focus.
The _______________ is the spot on Earth’s surface directly above the focus.
Types of Seismic Waves
______________________: originate at the focus
 Travel by stretching & compressing land as they pass (like a slinky)
 Travel faster through ____________ than liquid
_______________________: move land side to side
 Only travel through solids
___________________: move up and down on earth’s surface (like waves on a pond)
 Cause the most damage
Measuring Earthquakes
__________________ is the measure of the strength of an earthquake’s waves.
Magnitude is measured using a seismograph and a ___________ scale.
Seismographs
 Seismic waves cause the seismograph’s drum to vibrate. However, the suspended
weight with the pen attached moves very little. Therefore, the pen stays in place and
records the drum’s vibrations.
Locating the Epicenter
 Geologists use seismic waves to locate an earthquake’s epicenter.
Earthquake Risk
 Geologists can determine earthquake risk by locating where faults are __________
and where ____________ earthquakes have occurred.