Transcript File

Chapter 2 Lesson 3
How Do Movements Of The
Earth’s Crust Change
Landforms?
S5E1A: Students will identify features caused by
destructive/constructive processes
Vocabulary Preview
Plate: a section of Earth’s crust and
mantle that fits together with other
sections like puzzle pieces
 Earthquake: a shaking of the Earth’s
surface, caused by movement of rock in
the crust
 Epicenter: the point on Earth’s surface
directly above the focus of an earthquake
 Fault: a crack in the Earth’s surface

Vocabulary Preview
Magma: melted rock that is beneath
Earth’s surface
 Lava: molten rock that flows from a
volcano onto Earth’s surface
 Volcano: a mountain that forms as
molten rock flows through a crack onto
Earth’s surface

Earth’s Structure

Imagine you’re a miner digging for gold or
gems. You dig deep into Earth, maybe 1
or 2 miles down. But even at this depth,
you’ve barely scratched Earth’s surface.

You’d need to dig down about 4,000 miles
to reach the center of the Earth. What do
you think you’d find at the center?
Earth’s Structure

You would think maybe you would find rock, but you
wouldn’t. Earth has 4 layers-crust, mantle, outer core,
and the inner core.

If you could dig a hole to the center of the Earth, you’d
find that the layers are different from one another.
The thin crust is solid rock. The mantle also has a thin
crust.
But some rock within the mantle is soft, like melted
candy. The deeper you’d go, the hotter things would get.
The outer core is liquid, but it’s iron, not rock.
The inner core is also metal, but its solid due to intense
pressure.




Layers of the Earth
Crust 5-70 km (3-43
mi The crust is the
surface layer of
Earth.Mantle 2885
km (1790 mi)
The mantle has two
parts: the upper
mantle and the
lower mantle. Most
of the mantle is
solid rock, but some
mantle rock is soft.
Outer Core 2270 km
(1410 mi)
The hot outer core is
liquid iron.Inner
Core 1210 km (750
mi)
Inner core is iron
and nickel. Even
though the core is
very hot, great
pressure at the
center of Earth
keeps the inner core
solid.
Earth’s Structure





Earth’s crust and uppermost mantle are divided
into sections, called plates.
Plates are blocks of crust and upper mantle
rock that fits together like puzzle pieces.
Look at the map on the next slide. There are 10
major plates.
Most of North America, Greenland, and part of
the Atlantic Ocean are on the North American
Plate.
Part of California and most of the Pacific Ocean
are on the Pacific Plate.
Earth’s Structure
Plates “float” on the softer rock of the mantle.
As the rock flows, plates move.
 Because plates fit together so closely, the
movement of one plate affect the other plates.
 At different places, plates move toward each
other, away from each other, or alongside each
other. These plate movements cause many
changes in Earth’s surface.

Earth’s Structure
Earthquakes




Suppose you press your palms
together as hard as you can.
If one hand slips, energy is
released suddenly and your
hands move past each other.
When two of Earth’s plates
move suddenly past each
other, energy is also released
and the ground shakes.
An earthquake is movement
of the ground caused by a
sudden release of energy in
the Earth’s crust.
Earthquakes
The place within the crust where energy is
released during an earthquake is called
the focus.
 The release of energy may hardly be
noticed, or it may cause a lot of damage.
 The greatest damage is likely to occur
directly above the focus.
 The point on Earth’s surface directly above
the focus is called the epicenter.

An earthquake occurs when Earth’s crust moves and releases energy. The energy
of an earthquake spreads out like ripples on a pond. Places farther from the
epicenter are likely to experience less damage than places near the epicenter.
Earthquakes

Earthquakes are caused by three different types
of plate movement. Plates pushing together,
plates sliding past each other, and plates pulling
apart all produce earthquakes.

Most earthquakes occur along a fault, or break
in the Earth’s crust. Some faults occur in the
middle of plates, but most are found near the
edge of plates. Faults develop as plate
movements bend and crack the crust.
Earthquakes
Earthquakes caused by plates or pieces of crust
pushing together or sliding past each other are
usually very strong.
 Earthquakes caused by plates or pieces of crust
pulling apart are usually weak.
 Scientists classify earthquakes by estimating
their magnitude, or amount of energy being
released. This is reported using a scale of
magnitude.

Earthquakes






This scale is called the Richter Scale.
An earthquake measuring 2.0 on the scale is too
small to be felt.
There are millions of earthquakes like this every
year.
An earthquake measuring 6.0 or higher on the
Richter Scale can cause a great deal of damage.
Each increase of 1 on the Richter Scale is an
increase in strength of about 32 times.
About 20 earthquakes of magnitude 6.0 or
greater occur each year.
Major Earthquakes
Read the information in the
table. Then, on a world map,
mark the areas where these
major earthquakes occurred.
Using the information in the text
below, estimate how many times
stronger the 1964 Alaska
earthquake was than the 1976
China earthquake.
An earthquake in
Seattle in 2001
measured 6.8 on
the Richter scale
and caused a lot
of damage.
The pattern of
the rocks after an
earthquake
clearly show the
San Andreas
Fault. The map
shows the
location of this
fault
Volcanoes
You know that there are
places in Earth’s mantle
where solid rock melts.
 Melted, or molten, rock
beneath Earth’s surface is
known as magma.
 Magma forms in places
where plates push
against each other or pull
away from each other.
 Magma is less dense than
solid rock, so it’s pushed
upward through the
mantle and crust.

Volcanoes





As magma travels upward, it
sometimes reaches an
opening, or vent, in the crust.
Magma that has flowed out of
a vent is called lava.
Lava is molten rock that
reaches Earth’s surface.
As more and more lava flows
from a vent, a volcano begins
to form.
A volcano is a mountain made
of lava, ash, or other materials
from eruptions.
Volcanoes
Lava may ooze slowly out of a vent or it
may explode from a vent with tremendous
force.
 The 1883 eruption of Krakatoa in
Indonesia blew lava 17 miles into the air!

Krakatoa before 1883
Krakatoa after 1883
Volcanoes




Some volcanoes form above
an especially hot column of
magma.
This column is called a hot
spot. A hot spot can melt a
hole through the crust as the
magma rises to the surface.
As a plate moves slowly over
a hot spot, volcanoes form in
new locations. Eventually, a
hot spot can produce a chain
of volcanoes.
This is how the Hawaiian
Islands were formed.
Volcanoes
Composite, Shielded, Cinder Cone Volcanoes
How Mountains Form
Mountains are the tallest
landforms on Earth.
 They form where the
crust is crumpled and
pushed upward by the
movements of plates.
 Many mountains form
where plates come
together.
 The edge of the denser
plate is forced into the
mantle, while the dense
plate is pushed up.

How Mountains Form
The Appalachian Mountains are mostly the
result of normal faults folding and
thrusting upwards.
 The Valley and Ridge region, and the Blue
Mountains, on the other hand, were built
up by a series of reverse faults that force
large sheets of rock to pile up.
 The diagrams show two different ways
that faults can move.

How Mountains Form
Mountains may also form
in the middle of a plate.
 Suppose you hold a
cracker and push down
on the opposite edges.
 The cracker would soon
break, with jagged,
broken edges in the
center moving up.
 This is how the Grand
Teton Mountains in
Wyoming, formed.

How Mountains Form
Millions of years ago, surrounding plates
put tremendous pressure on the edges of
the N. American plate.
 The pressure snapped a block of rock in
the middle of the plate.
 The rock rose up from the land around it,
forming mountains.

Cloudland Canyon State Park in northern Georgia
was produced by the movement of faults.
The layers of rock in this mountain in Montana
are the result of reverse faults.
In a normal fault, the
rock layers above the
fault move down
In a reverse fault, the
rock layers above the
fault move up.
How Mountains Form
Plates that move apart leave gaps
between them.
 When this happens, mantle rock moves in
to fill the gaps.
 Magma builds up along plate boundaries,
forming a ridge.
