Transcript Chapter C-1 Lesson 2

Chapter C-1 Lesson 2
Mountains,volcanoes, and
earthquakes
Earth’s interior
The earth is not a solid ball of rock.
Instead, it has three distinct layers:
 The crust
 The mantle
 The core
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The Crust
The crust is the outer layer, and is
made of rock.
 It is very thin compared to the other
layers.
 If the Earth was an egg, the crust
would be thinner than the egg’s shell.
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The Mantle
The layer of rock beneath the Earth’s
crust.
 Just under the crust, the mantle is solid.
But the mantle is very hot, and the
deeper you go, it gets like melted
candy.
 We only see this when it comes to the
surface through volcanoes.
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The Core
The core is the center layer of the
Earth.
 It is the hottest layer, and is divided
into 2 parts:
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An outer core of molten or liquid iron.
An inner core of solid iron.
Three Layers of the Earth
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Crust
Mantle
Core
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Outer core
Inner core
Earth’s crust moves
The surface of the earth is not one solid
piece. It is made up of many floating
plates.
 Def : Plates: are rigid blocks of crust
and upper mantle rock.
 Most of N. America, Greenland and the
western half of the North Atlantic Ocean
are on the North American Plate.
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Earth’s Crust Moves
Part of California and most of the Pacific
Ocean make up the Pacific plate.
 There are 12 major plates in all, and
they all fit together like a jigsaw puzzle.
 They float on the mantle’s soft rock.
 Plate movement is very slow, about a
few centimeters each year.
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Earth’s Crust Moves
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Each plate’s movement affects the
surrounding plates.
Earth’s Crust Moves
When plates collide, energy is released
and new landforms are made.
 On land this is how mountains are
made and volcanoes form.
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Earth’s Crust Moves
When plates pull apart, a rift or crack
forms. These cracks are what we call
valleys.
 Volcanoes can form above or under the
oceans where plates pull apart.
 When plates pull apart under the sea,
ridges form, and new sea floor
develops.
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Earth’s Crust Moves
When plates slide and scrape past each
other, they stick until they slide or slip.
 This is what we call earthquakes.
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Earth’s Crust Moves
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This is a picture of the San Andreas
fault line in California. It shows the
crack that is forming in the crust.
Mountain formation
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Mountains form as the crust folds,cracks and
bends due to plate movement.
Many of the highest mountains form where
two plates are colliding into each other.
The “wrinkle” or mountains may form some
distance away, not always right at the edge
of where the plates bump into each other.
Mountain formation
When plates pull apart, the gap allows
magma to break through.
 Def : Magma: molten rock from the
mantle layer.
 Magma builds up and forms long chains
of mountains under the ocean mostly.
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Volcanoes
Volcanoes formed when molten magma
exploded to the Earth’s surface.
 A volcano is a mountain formed of lava
and ash.
 Def : lava- is magma that reaches the
earth’s surface.
 Def : ash- small pieces of hardened
lava.
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Volcanoes
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Chains of volcanoes form when one
plate is pushed underneath another
plate.
Volcanoes
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The leading edge of the plate that is pushed under
melts as it sinks into the mantle.
The melted rock becomes magma that forces itself
up between the plates.
Sometimes volcanoes form in the middle of plates,
over hot spots of magma. The magma melts a hole in
the plate and rises up through the hole, causing an
eruption.
The Hawaiian islands formed this way. New islands
are forming in this chain.
Each island is a distinct result of how the lava and
ash escape through the openings or vents of the
volcano.
Earthquakes
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Def :earthquake- is a shaking of the ground
caused by the sudden release of energy (a
slip)in the earth’s crust.
This energy comes from plates crushing
together, scraping past, or bending along
jagged lines of the plates.
Earthquakes are very common, more than a
million occur every year.
Some are very strong,and some are barely
felt by the inhabitants that live above them.
Earthquakes
Many earthquakes occur along the
Pacific Plate.
 The earth’s crust can break apart,
forming faults.
 Def :faults-places where pieces of the
crust move apart.
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Earthquakes
Earthquakes send out energy in the
form of seismic waves.
 Def :seismic waves-are waves of energy
traveling through the crust.
 They are like ripples that form on a
pond when a stone is tossed in.
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Questions to answer
Describe three ways in which Earth’s
plates interact.
 1.push together
 2.pull apart
 3.slide past each other
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Questions to Answer
Q: What is magma and where does it
come from?
 A: magma is molten rock that comes
from the lower mantle.
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Questions to Answer
Q: How do volcanoes form where
oceanic and continental plates collide?
 A:the leading edge of the oceanic plate
is pushed deep into the mantle where
the rock melts and magma rises to the
surface between the plates.
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Questions to Answer
Q: If one plate is pushing away from
the plate next to it on one side, what
must be happening to the boundary
with another plate on the other side?
 A: The plate is colliding with the plate
next to it on the opposite side.
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Questions to Answer
Q: Many strong earthquakes are caused
by A:plates sliding past each other
 B:lava flowing down the side of a
volcano
 C: plates spreading apart
 D: hot magma
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