Transcript Lesson 1 - Milan C-2 School District

Chapter Introduction
Lesson 1 Plate Tectonics
Lesson 2 Earthquakes
and Volcanoes
Lesson 3 Weathering,
Erosion, and
Deposition
Chapter Wrap-Up
How do natural
processes change
Earth’s surface over
time?
What do you think?
Before you begin, decide if you agree or
disagree with each of these statements.
As you view this presentation, see if you
change your mind about any of the
statements.
Do you agree or disagree?
1. Continents do not move.
2. Earth’s mantle is liquid.
3. Earthquakes occur and volcanoes
erupt only near plate boundaries.
4. Volcanoes erupt melted rock.
Do you agree or disagree?
5. Rocks cannot change.
6. Sediment can be transported by water,
wind, and ice.
Plate Tectonics
• What is the theory of plate tectonics?
• What evidence do scientists use to
support the theory of plate tectonics?
• How do the forces created by plate
motion change Earth’s surface?
Plate Tectonics
• plate tectonics
• transform
boundary
• continental drift
• subduction
zone
• convergent
boundary
• compression
• tension
• divergent
boundary
• shear
Plate Motion
• The theory of plate
tectonics states that
Earth’s crust is broken
into rigid plates that
move slowly over
Earth’s surface.
• The rigid plates are
called tectonic plates.
• North America is part of
the North American Plate.
Plate Motion (cont.)
• The movement of one plate is described
as either moving away from or toward
another plate, or sliding past another
plate.
• Plates move at speeds of only a few
centimeters per year.
• At this rate, it takes moving plates
millions of years to make new continents,
new mountain ranges, or other
landforms.
Plate Motion (cont.)
What is the theory of plate
tectonics?
Plate Motion (cont.)
Long before
geologists proposed
the theory of plate
tectonics, they
discovered evidence
of continental
movement.
Photo by G.K. Gilbert, U.S. Geological Survey
Plate Motion (cont.)
• In 1912, Alfred
Wegener developed
the hypothesis that
continents move,
called continental
drift.
• One piece of
evidence is the
shape of Earth’s continents.
Plate Motion (cont.)
Fossil and rock
evidence from the
Gondwana continents
also supports the
hypothesis of
continental drift.
Geologists have discovered the same types
of fossils on continents that are now
separated by vast oceans.
Plate Motion (cont.)
What evidence do scientists
use to support the theory of
plate tectonics?
Plate Motion (cont.)
• Convection affects the mantle
underneath tectonic plates.
• Hotter mantle rises toward Earth’s
surface and cooler mantle sinks deeper
into the mantle.
Plate Motion (cont.)
As the Earth’s mantle moves, it pushes
and pulls tectonic plates over Earth’s
surface.
Tectonic Plate Boundaries
• The edges of tectonic plates are called
plate boundaries.
• A convergent boundary is where two
plates move toward each other.
• A divergent boundary is where two
plates move apart from each other.
• A transform boundary is where plates
slide horizontally past each other.
• When two plates come together, the
denser oceanic plate usually is forced
down into the mantle and the less dense
continental plate remains on Earth’s
surface.
• The area where
one plate slides
under another
is called a
subduction zone.
Tectonic Plate Boundaries (cont.)
• When two continents collide at a plate
boundary, both continents remain on the
surface.
• As two continents
push together,
the crust rises
up and large
mountains form.
Tectonic Plate Boundaries (cont.)
• When plates move apart at divergent
boundaries, a rift forms between the two
plates.
• A rift can form within continents when
continental crust
moves in
opposite
directions.
Tectonic Plate Boundaries (cont.)
• A rift also can form at divergent
boundaries on the ocean floor.
• As plates separate,
molten rock can
erupt from the rift.
• As the molten rock
cools, it forms new
crust.
Tectonic Plate Boundaries (cont.)
• Tectonic plates slide past each other at
transform boundaries.
• The two sides of the
boundary move in
opposite directions.
• This can deform or
break features such
as fences, railways,
or roads that cross
the boundary.
Tectonic Plate Boundaries (cont.)
transform
Science Use horizontal relative
motion
Common Use to change
Forces Changing Earth’s Surface
• Forces within Earth cause plates to
move.
• The three types of plate boundaries
experience different types of forces.
• The squeezing force at a convergent
boundary is called compression.
• The pulling force at a divergent boundary
is called tension.
• The side-by-side
dragging force at
transform
boundaries
is called
shear.
Forces Changing Earth’s Surface (cont.)
• Even though plates move slowly, the
forces at plate boundaries are strong
enough to form huge mountains and
powerful earthquakes.
• Tensional forces pull the land apart and
form rift valleys and mid-ocean ridges.
• Compressional forces form mountains.
Forces Changing Earth’s Surface (cont.)
How do the forces created by
plate motion change Earth’s
surface?
• Evidence of continental drift includes
fossils, mountain ranges, rock types,
and the shapes of continents.
• Earth’s crust is broken into pieces
called tectonic plates. Convection
currents in the mantle
cause the plates
to move.
• There are three types of tectonic plate
boundaries. Movement occurs at all
three boundaries.
Which boundary is between two
plates moving toward each other?
A. convergent
B. divergent
C. subduction
D. transform
Which zone describes the
boundary where one plate slides
under another plate?
A. convergent
B. divergent
C. subduction
D. transform
Which is the side-by-side
dragging force at transform
boundaries?
A. shear
B. tension
C. compression
D. continental drift
Do you agree or disagree?
1. Continents do not move.
2. Earth’s mantle is liquid.
Earthquakes and Volcanoes
• What causes earthquakes?
• What causes volcanoes to form?
• How do earthquakes and volcanoes
change Earth’s surface?
Earthquakes and Volcanoes
• earthquake
• lava flow
• fault
• volcanic ash
• mid-ocean ridge
• caldera
• hot spot
Earthquakes
• Because tectonic plates move very
slowly, most changes to Earth’s surface
take a long time.
• But some changes occur very quickly
and violently.
An earthquake is the rupture and sudden
movement of rocks along a break or a
crack in Earth’s crust.
Dr. Roger Hutchinson/NOAA
Earthquakes (cont.)
• The surface along
which the crust
moves is called a
fault.
• When pieces of crust
slide past each other,
energy is released,
causing the ground
to shake.
Photograph by N.J. Silberling, USGS Photo Library, Denver, CO
Earthquakes (cont.)
What causes earthquakes?
Most earthquakes occur near plate
boundaries, though some occur very far
from plate boundaries.
Earthquakes (cont.)
• Compression and tension forces produce
ridges and mountains as Earth’s crust
moves vertically.
• Liquefaction refers to when extreme
shaking causes ground that is made up
of loose sediment to behave more like a
liquid than a solid.
• Earthquakes can trigger landslides,
which bring rocks and soil from the tops
of mountains into valleys.
Earthquakes (cont.)
Earthquakes that happen underwater can
cause tsunamis—huge ocean waves
created by movement at a fault.
Earthquakes (cont.)
How do earthquakes change
Earth’s surface?
Volcanoes
• Volcanoes are landforms that form when
magma erupts onto Earth’s surface as
lava.
• Volcanoes can occur at divergent and
convergent plate boundaries and at hot
spots.
The mountains that form as lava from a
volcano at a divergent boundary builds up
and cools are called mid-ocean ridges.
At some convergent boundaries, one
tectonic plate sinks, melts the mantle, and
forms magma that erupts onto the plate
that does not sink.
Volcanoes (cont.)
• Hot spots are locations where
volcanoes form far from plate
boundaries.
• The Hawaiian Islands in the middle of
the Pacific Ocean and Yellowstone
National Park in Wyoming are hot spots.
Volcanoes (cont.)
• Because magma is hot, it is also less
dense than the rock material around it.
• Rising magma and great pressure
caused by dissolved gases eventually
erupt through cracks in Earth’s surface,
creating a volcano.
Most of Earth’s largest volcanoes are
located at convergent plate boundaries.
Volcanoes (cont.)
What causes volcanoes to form?
Volcanoes (cont.)
• When melted
mantle material
erupts, it flows
over Earth’s
surface, creating
long streams of
molten rock
called lava flows.
Royalty-Free/CORBIS
• The lava eventually cools and solidifies,
forming solid rock.
Volcanoes (cont.)
• At convergent plate boundaries, part of
the continental crust can become mixed
with magma from the mantle.
• When this mixture of molten materials
erupts, it does not flow as easily as lava
made only of melted mantle.
• Instead of forming lava flows, it often
solidifies in the atmosphere, where it
breaks into small pieces of lava called
volcanic ash.
Volcanoes (cont.)
• Eruptions that eject ash high into the
atmosphere are called explosive
eruptions.
• Lava also can be produced during these
eruptions.
• Shield volcanoes form after basaltic lava
flows have occurred over time.
• Shield volcanoes tend to be large with
gentle slopes.
J.S. Griggs/U.S. Geological Survey
• Composite volcanoes form as lava flows
and ash layers deposited by explosive
eruptions build up.
• Composite volcanoes often have steep
sides and a cone shape.
PhotoLink/Getty Images
Before a volcano erupts, magma builds up
in the crust in a reservoir called a magma
chamber.
Sometimes the surface above the chamber
collapses, creating a large depression in
the center of the volcano called a caldera.
P.W. Lipman, U.S. Geological Survey
Volcanoes (cont.)
caldera
from Latin caldārium, means
“warming”
• Volcanic ash and gases from explosive
eruptions can blow high into the
atmosphere, blocking sunlight.
• This can
cause the
temperature
of the
atmosphere
near Earth’s
surface to
decrease.
P.W. Lipman, U.S. Geological Survey
Volcanoes (cont.)
How do volcanoes change
Earth’s surface?
• Earthquakes occur when movement
along a fault occurs. Earthquakes
occur mostly along plate boundaries.
They can cause great damage.
• Volcanoes form at two types of plate
boundaries. Lava cools and builds
up, forming volcanoes and other
landforms.
• Earthquakes and volcanoes change
the surface by building mountains,
covering land with lava, and shifting
the surface along faults.
Which happens when extreme
shaking causes sediment to
behave more like a liquid than
a solid?
A.
B.
C.
D.
compression
eruption
liquefaction
tsunami
Which is a long stream of molten
rock which eventually cools,
solidifies, and builds up over time
as flat layers?
A. mid-ocean ridge
B. lava flow
C. fault
D. caldera
Which type of volcano often has
steep sides and is cone shaped?
A. caldera
B. composite
C. mid-ocean
D. shield
Do you agree or disagree?
3. Earthquakes occur and volcanoes
erupt only near plate boundaries.
4. Volcanoes erupt melted rock.
Weathering, Erosion, and
Deposition
• How are weathering and soil formation
related?
• How do weathering, erosion, and
deposition change Earth’s surface?
• How are erosion and deposition
related?
Weathering, Erosion, and
Deposition
• weathering
• soil
• erosion
• sediment
• physical weathering
• deposition
• chemical weathering
Weathering
• Weathering refers to the processes that
break down rocks, changing Earth’s
surface over time.
• Erosion is the moving of weathered
material, or sediment, from one location
to another.
Weathering
(cont.)
Slowly but surely, weathering and erosion
wear down mountains.
Photo by Tim McCabe, USDA Natural Resources Conservation Service
Dr. Parvinder Sethi
Weathering
(cont.)
• The process of breaking rock into small
pieces without changing the composition
of the rock is physical weathering.
• Frost wedging is what occurs when
water in rocks freezes and melts
repeatedly, breaking the rocks apart.
Weathering
(cont.)
The roots of plants
can grow into cracks
in rock and
eventually break the
rock.
Weathering
(cont.)
• The process of changing the composition
of rock and minerals by exposure to
water and the atmosphere is called
chemical weathering.
• Gases in the atmosphere can cause
chemical weathering.
Weathering
(cont.)
How does weathering change
Earth’s surface?
Weathering
(cont.)
• Physical weathering exposes more
surface area of rocks, allowing more
water and atmospheric gases to enter
rocks.
• Chemical weathering weakens rocks by
changing the composition of some
minerals and dissolving others.
Weathering
(cont.)
• Soil consists of weathered rock, mineral
material, water, air, and organic matter
from the remains of organisms.
• Soil forms directly on top of the rock
layers from which it is made and is the
result of hundreds to thousands of years
of weathering.
Soil formation begins when physical and
chemical weathering break down rocks.
Soil formation begins when physical and
chemical weathering break down rocks.
Weathering
(cont.)
• Warm, wet climates produce soil fastest.
• Large amounts of rain can speed
weathering of rocks, and chemical
reactions are faster in warmer
temperatures.
Weathering
(cont.)
How are weathering and soil
formation related?
Erosion
• The minerals and small pieces of rock
produced by weathering are called
sediment.
• Moving water causes erosion by picking
up rock pieces and sediment, which
scrape along the ground picking up more
material.
• Large masses of ice, called glaciers,
cause erosion by flowing down a
mountain and removing rock and
sediment.
• Erosion by
glaciers makes
deep valleys
and steep
peaks.
• Strong winds also can erode and move
sediment.
• Soil and rock that are not protected by
plants can be eroded by wind.
U.S. Department of Agriculture
Erosion (cont.)
How does erosion change
Earth’s surface?
Deposition
• Deposition is the process of laying
down eroded material in a new location.
• If the speed of flowing water decreases,
the water can no longer carry sediment
and the sediment settles at the bottom of
the water.
• Floodplains form when sediment settles
out of rivers that flood the areas next to
them.
• When glaciers melt, the water produced
by the melting ice does not flow fast
enough to carry sediment.
• Glacial deposits of sediment are called
moraines.
• Wind also can deposit sediment.
• Sand dunes are landforms made as wind
continually moves and deposits sand
grains.
Tim McCabe/NRCS
Deposition (cont.)
How does deposition change
Earth’s surface?
Deposition (cont.)
• The locations where sediment
accumulates are called sedimentary
basins.
• Sediment continues to be deposited in
low areas and then forced upward as
tectonic activity forms mountains.
Deposition (cont.)
How are erosion and
deposition related?
• Physical and chemical weathering
work together and change Earth’s
surface. They break down rock and
form sediment.
• Erosion occurs when sediment is
removed and transported from where
it formed.
• Deposition occurs when sediment is
laid down in new locations.
Which process breaks rock into
small pieces without changing
the composition of the rock?
A. deposition
B. erosion
C. chemical weathering
D. physical weathering
Which are the minerals and small
pieces of rock produced by
weathering?
A. glaciers
B. sand dunes
C. sediment
D. soil
Which location accumulates
sediment?
A. soil
B. glacier
C. sand dune
D. sedimentary basin
Do you agree or disagree?
5. Rocks cannot change.
6. Sediment can be transported by water,
wind, and ice.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Mountains and valleys
form where tectonic
plates interact, new
crust forms where lava
flows from volcanoes,
and the land shifts
when earthquakes
occur.
Lesson 1: Plate Tectonics
• The theory of plate tectonics states that Earth’s
surface is broken into rigid pieces, or plates, that
move with respect to each other.
• Evidence that continents have moved throughout
Earth’s history includes the shape of the continents
and the presence of similar fossils and geological
features on widely separated continents.
• The forces produced by plate motion
change Earth’s surface by forming
mountains and rifts and by causing
earthquakes and volcanic
eruptions.
Lesson 2: Earthquakes and Volcanoes
• Earthquakes are caused when forces on rocks in
the crust become large enough for the rock to move
along faults.
• Volcanoes form when rocks in the mantle become
hot enough to melt and the molten rock erupts onto
Earth’s surface.
• Earthquakes and volcanoes change Earth’s surface
in several ways. They form mountains and new
landmasses from lava flows and explosive
eruptions.
Lesson 3: Weathering, Erosion, and
Deposition
• Physical weathering and chemical weathering break
down material on Earth’s surface. Soil can form as a
result.
• Weathering changes Earth’s surface by breaking
down material and forming soil. Erosion and
deposition by water, wind, and ice create and
change landforms.
• Sediment is removed by erosion, and deposition
lays down sediment in a new location.
Alfred Wegener proposed which
hypothesis in 1912?
A. compression
B. continental drift
C. plate tectonics
D. transform boundaries
Which describes the pulling force
at a divergent boundary?
A. compression
B. continental drift
C. shear
D. tension
Which form as lava at a divergent
boundary that builds up and cools?
A. faults
B. hot spots
C. mid-ocean ridges
D. tsunami
Where do volcanoes form far
from plate boundaries?
A. above earthquakes
B. between mid-ocean ridges
C. over hot spots
D. under faults
Which is the movement of
sediment from one location to
another?
A. deposition
B. erosion
C. chemical weathering
D. physical weathering
Which theory states that Earth’s
crust is broken into rigid plates
that move slowly over Earth’s
surface?
A.
B.
C.
D.
convection
continental drift
divergent boundaries
plate tectonics
Which force forms rift valleys and
mid-ocean ridges?
A. tension
B. shear
C. convection
D. compression
Which is the rupture and sudden
movement of rocks along a break
or a crack in Earth’s crust?
A. earthquake
B. fault
C. lava flow
D. volcano
Which is molten material that
solidifies in the atmosphere and
breaks into small pieces of lava?
A. volcanic ash
B. mid-ocean ridge
C. lava flow
D. hot spot
Which process changes the
composition of rock and minerals
by exposure to water and the
atmosphere?
A. deposition
B. erosion
C. chemical weathering
D. physical weathering