Chapter C-1 Lesson 2

1
Chapter C-1 Lesson 2

• Mountains,volcanoes, and earthquakes

2
Earths interior

• The earth is not a solid ball of rock. Instead,
  it has three distinct layers
• The crust
• The mantle
• The core

3
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 eggs shell.

4
The Mantle

• The layer of rock beneath the Earths 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.

5
The Core

• The core is the center layer of the Earth.
• It is the hottest layer, and is divided into 2
  parts
• An outer core of molten or liquid iron.
• An inner core of solid iron.

6
Three Layers of the Earth

• Crust
• Mantle
• Core
• Outer core
• Inner core

7
Earths 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.

8
Earths 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 mantles soft rock.
• Plate movement is very slow, about a few
  centimeters each year.

9
Earths Crust Moves

• Each plates movement affects the surrounding
  plates.

10
Earths Crust Moves

• When plates collide, energy is released and new
  landforms are made.
• On land this is how mountains are made and
  volcanoes form.

11
Earths 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.

12
Earths Crust Moves

• When plates slide and scrape past each other,
  they stick until they slide or slip.
• This is what we call earthquakes.

13
Earths Crust Moves

• This is a picture of the San Andreas fault line
  in California. It shows the crack that is forming
  in the crust.

14
Mountain formation

• 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.

15
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.

16
Volcanoes

• Volcanoes formed when molten magma exploded to
  the Earths surface.
• A volcano is a mountain formed of lava and ash.
• Def lava- is magma that reaches the earths
  surface.
• Def ash- small pieces of hardened lava.

17
Volcanoes

• Chains of volcanoes form when one plate is pushed
  underneath another plate.

18
Volcanoes

• 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.

19
Earthquakes

• Def earthquake- is a shaking of the ground
  caused by the sudden release of energy (a slip)in
  the earths 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.

20
Earthquakes

• Many earthquakes occur along the Pacific Plate.
• The earths crust can break apart, forming
  faults.
• Def faults-places where pieces of the crust move
  apart.

21
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.

22
Questions to answer

• Describe three ways in which Earths plates
  interact.
• 1.push together
• 2.pull apart
• 3.slide past each other

23
Questions to Answer

• Q What is magma and where does it come from?
• A magma is molten rock that comes from the lower
  mantle.

24
Questions to Answer

• Q How do volcanoes form where oceanic and
  continental plates collide?
• Athe 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.

25
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.

26
Questions to Answer

• Q Many strong earthquakes are caused by-
• Aplates sliding past each other
• Blava flowing down the side of a volcano
• C plates spreading apart
• D hot magma