Chapter Introduction
Lesson 1 Earth’s Moving
Surface
Lesson 2 Shaping
Earth’s
Surface
Lesson 3 Changing
Earth’s Surface
Chapter Wrap-Up
What processes change
Earth’s surface?
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. Earth’s surface is made up of tectonic
plates.
2. Tectonic plate motion is too slow to
measure.
3. Most earthquakes occur near tectonic
plate boundaries.
4. Volcanoes can erupt anywhere.
Do you agree or disagree?
5. Wind erosion only occurs in the desert.
6. Rivers are the only cause of erosion.
Earth’s Moving Surface
• What is the theory of plate tectonics?
• What are the differences between
divergent, convergent, and transform
plate boundaries?
• What causes tectonic plates to move
on Earth’s surface?
Earth’s Moving Surface
• plate tectonics
• lithosphere
• asthenosphere
• divergent
boundary
• convergent
boundary
• subduction
• transform
boundary
• convection
Plate Tectonics
• The theory of plate tectonics states that
Earth’s surface is broken into large, rigid
pieces that move with respect to each
other.
• These pieces, or tectonic plates, move
slowly over Earth’s surface.
Tectonic plate motion and other processes
have affected North America. The western
United States has tall mountains, while the
central region is flat.
Plate Tectonics (cont.)
What is the theory of plate
tectonics?
Plate Tectonics (cont.)
tectonic
from Greek tekton, means
“builder”
Plate Tectonics (cont.)
• The Earth’s crust and
uppermost part of the
mantle make up the
lithosphere.
• The lithosphere forms a
rigid shell on the outside
of Earth which is broken
into tectonic plates.
Scientists have identified 15 large tectonic
plates.
Plate Tectonics (cont.)
• The partially melted
portion of the mantle
below the lithosphere is
the asthenosphere.
• The asthenosphere is
hotter than the
lithosphere and can
bend more easily.
Plate Boundaries
• Scientists describe the movement of
tectonic plates, in terms of relative
motion—how it moves in relation to
another plate.
• As plates move relative to each other,
they form different types of boundaries.
• The type of boundary depends on the
relative motion of the plates.
Plate Boundaries (cont.)
• A boundary
where two plates
move away from
each other is
called a
divergent
boundary.
• As plates at a divergent boundary move
apart, new crust forms between them.
Plate Boundaries (cont.)
• A boundary where
two plates move
toward each other
is a convergent
boundary.
• In some convergent boundary locations,
one plate is pushed under the other plate
and down into the mantle where it melts
and becomes part of the mantle.
Plate Boundaries (cont.)
Subduction is the
process that occurs
when one tectonic
plate moves under
another tectonic plate.
Plate Boundaries (cont.)
Two plates slide
past each other
at a transform
boundary.
Plate Boundaries (cont.)
What are the differences
between divergent, convergent,
and transform plate boundaries?
Measuring Plate Movement
• Tectonic plates move horizontally over
Earth's surface.
• During the 1970s, scientists and
engineers developed new technologies
that enabled them to measure how fast
tectonic plates move.
• The position of any point on Earth’s
surface can be accurately measured
using the network of satellites known as
the Global Positioning System (GPS).
North America and Europe once were part
of a large continent called Pangaea. Over
time, tectonic plate motion broke apart the
supercontinent Pangaea.
Measuring Plate Movement (cont.)
• A divergent boundary formed between
North America and Europe about 200
million years ago.
• The plates moved apart, and the Atlantic
Ocean formed.
• North America is separating from Europe
at an average rate of just 2.5 cm per
year.
Why do tectonic plates move?
• The circulation within fluids caused
by differences in density and thermal
energy is called convection.
• Convection occurs in Earth’s
asthenosphere, just below the
lithosphere.
Why do tectonic plates move? (cont.)
Convection in the mantle can drag plates
over Earth’s surface.
Why do tectonic plates move? (cont.)
• Another process that causes plate
movement is subduction.
• When two plates collide, one can
subduct or sink into the hotter, lessdense mantle.
• When this happens, the rest of plate is
pulled along behind the sinking part of
the plate.
Why do tectonic plates move? (cont.)
What causes tectonic plates
to move?
• Earth’s lithosphere is
broken into pieces called
plates. These plates
move on Earth’s surface
and interact in three
different ways.
• GPS can be
used to measure
and track plate
movement.
• Convection in the mantle causes
tectonic plates to move across Earth’s
surface.
Which term refers to a location
where two plates slide past each
other?
A. asthenosphere
B. lithosphere
C. divergent boundary
D. transform boundary
At about what rate is North
America separating from Europe?
A. 2.5 centimeters per day
B. 2.5 centimeters per year
C. 2.5 meters per year
D. 2.5 miles per year
Which is the partially melted
portion of the mantle below the
lithosphere?
A. divergent boundary
B. transform boundary
C. tectonic plate
D. asthenosphere
Do you agree or disagree?
1. Earth’s surface is made up of tectonic
plates.
2. Tectonic plate motion is too slow to
measure.
Shaping Earth’s Surface
• Where do most earthquakes occur?
• How are landforms related to plate
tectonics?
• Where do most volcanoes form?
• How does plate movement form
mountains?
Shaping Earth’s Surface
• earthquake
• volcano
• fault
• mid-ocean ridge
• magma
• lava
Earthquakes
An earthquake is the vibrations caused by
the rupture and sudden movement of rocks
along a break or a crack in Earth’s crust.
The strong shaking of Earth’s surface can
damage both natural features and humanmade structures.
USGS photo by Walter D. Mooney
USGS
• Earthquakes occur
at faults.
• A fault is a crack or
a fracture in Earth’s
crust along which
movement occurs.
• Convection currents
beneath tectonic
plates force the rocks
on either side of the
fault to move.
Photograph by N.J. Silberling, USGS Photo Library, Denver, CO
Earthquakes (cont.)
fault
Science Use a fracture in the
crust of a planet
Common Use responsibility for
wrongdoing or failure
The magnitude of an earthquake refers
to how much energy is released during
an earthquake.
Earthquakes (cont.)
• Most earthquakes occur at plate
boundaries.
• A plate boundary is made up of more
than one fault and covers a large region.
• Faults are largest where one plate
subducts into the mantle, and the
strongest earthquakes occur at these
locations.
The convergent boundary between the Indian
Plate and the Burma Plate (part of the
Eurasian Plate)
ruptured in 2004.
The area of the
rupture is indicated
in green on the
map. Smaller
earthquakes have
occurred in the
purple areas.
Earthquakes (cont.)
Where do most earthquakes
occur?
• Different types of movement occur at the
three types of plate boundaries.
• At a transform boundary, blocks of crust
move horizontally past each other.
• Features that cross the
fault, such as streams,
are shifted both by
plate movement and
by earthquakes.
• At divergent boundaries between
oceanic plates, mid-ocean ridges form.
• Between continental plates, one side of
the fault moves down relative to the
other side of the fault.
• Normal faults form
valleys at these
boundaries.
• At subduction zones of convergent
boundaries, the plate that does not
subduct deforms and crumples as the
two plates push toward each other.
• As the mantle near the
subducted plate melts,
magma rises and
forms a volcanic arc
on the plate that does
not subduct.
• At convergent boundaries with no
subduction, the edges of both tectonic
plates become crumpled and deformed.
• Because neither plate subducts, blocks
of crust slide upward
along a complex series
of faults called reverse
faults.
• This results in the
formation of tall
mountains.
Earthquakes (cont.)
How are landforms related to
plate tectonics?
Volcanoes
Volcanoes are vents in Earth’s crust
through which molten rock flows.
• Geologists call molten rock stored
beneath Earth’s surface magma.
• Lava is magma that erupts onto Earth’s
surface.
Volcanoes (cont.)
• Most volcanoes form at convergent plate
boundaries.
• A line of volcanoes forms parallel to the
plate boundary directly above the plate
that subducted.
Volcanoes (cont.)
The volcanoes in
Washington and
Oregon, such as
Mount Rainier and
Mount St. Helens
formed above the
subducting Juan de
Fuca Plate.
Volcanoes (cont.)
Where do most volcanoes form?
Sometimes, lava spreads over large areas
of Earth’s surface as a lava flow before
cooling and hardening.
Royalty-Free/CORBIS
At other times, volcanoes erupt explosively,
blowing ash high into the atmosphere.
P.W. Lipman, U.S. Geological Survey
Ocean Basins
• When a volcano erupts, lava hardens
and forms new crust.
• At an oceanic divergent plate boundary,
the newly formed crust is added to the
edges of the plates as new ocean crust.
• As the plates move apart, more lava fills
in the space and forms more ocean
crust.
Ocean Basins (cont.)
• Mid-ocean ridges are long, narrow
mountains formed by magma at
divergent boundaries.
• Most mountains form near plate
boundaries where folding and crumpling
of Earth’s crust usually occurs.
Ocean Basins (cont.)
Ocean Basins (cont.)
• When two continents collide at a
convergent plate boundary, large
mountain ranges form.
• Over millions of years, tectonic motion
can move mountain chains.
The Appalachian Mountains in North America
and the Caledonian mountains in Eurasia
formed at the same convergent boundary.
Over time, plate motion separated the
mountains.
Ocean Basins (cont.)
How does plate movement
form mountains?
• Interactions between plates cause
the crust to either spread apart and
form valleys or to deform and form
mountains.
• Earthquakes occur when stresses or
forces on a fault cause the crust on
either side of the fault to move.
• Volcanic mountains form at
subduction zones, where the plate
melts and magma erupts through
Earth’s crust.
Which causes forces along faults
that eventually result in
earthquakes?
A. convection currents
B. lava
C. magma
D. magnitude
Where do most earthquakes
occur?
A. at a mid-ocean ridge
B. at a plate boundary
C. at a volcano
D. in the asthenosphere
Which term refers to the long,
narrow mountains formed by
magma at divergent boundaries?
A. crust
B. fault
C. mid-ocean ridge
D. volcano
Do you agree or disagree?
3. Most earthquakes occur near tectonic
plate boundaries.
4. Volcanoes can erupt anywhere.
Changing Earth’s Surface
• What is the difference between
physical and chemical weathering?
• How do water, ice, and wind change
Earth’s surface?
Changing Earth’s Surface
• weathering
• erosion
• sediment
• deposition
• physical weathering
• mass wasting
• chemical weathering
• glacier
Breaking Down Earth Materials
• Weathering refers to the mechanical
and chemical processes that change
Earth’s surface over time.
• The processes of weathering can break,
scrape, smooth, or chemically change
rock.
Breaking Down Earth Materials (cont.)
• Sediment is the material formed from
rocks broken down by weathering.
• Sediment can be rock fragments, sand,
silt, or clay.
Breaking Down Earth Materials (cont.)
• Physical weathering is the process of
breaking down rock without changing the
composition of the rock.
• Physical weathering can occur because
of forces from plate motion, rupturing
faults, and changes in weather.
Breaking Down Earth Materials (cont.)
• When water in a
rock freezes, the
expanding ice can
shatter the rock.
• The force from the
growing roots of
plants can pry open
rock.
PhotoAlto
Breaking Down Earth Materials (cont.)
• Some minerals can react with water, air,
or substances in water and air, such as
carbon dioxide (CO2).
• Chemical weathering is the process
that changes the composition of rocks.
• Some minerals can dissolve in slightly
acidic water, such as rainwater.
Breaking Down Earth Materials (cont.)
• Other minerals react with air and water
to form new minerals.
• Chemical weathering and physical
weathering affect each other.
Breaking Down Earth Materials (cont.)
How does plate movement
form mountains?
Moving Earth Materials
• Weathering produces smaller rocks,
which can be moved more easily.
• Geologists use the term erosion to
describe the moving of weathered
material, or sediment, from one location
to another.
• Deposition is the laying down or settling
of eroded material.
Moving Earth Materials (cont.)
• Mass wasting is the
downhill movement of
a large mass of rocks
or soil due to gravity.
• The force of gravity
can create landslides,
a type of mass
wasting.
Photograph by R.L. Schuster, U.S. Geological Survey
Moving Earth Materials (cont.)
• Most erosion and transport of sediment
occurs by flowing water.
• Large rivers cause the most erosion.
• As water slows, the sediment in the
water is deposited on the sides of the
river.
• Sediment also is deposited when rivers
enter oceans or lakes, creating land
features called deltas.
• Sometimes, wind is strong enough to
cause erosion.
• Sand dunes and ripples are examples of
landforms made by wind.
Tim McCabe/NRCS
Ice
Large masses of ice, formed by snow
accumulation on land, that move slowly
across Earth’s surface are called glaciers.
• Sliding and flowing ice can weather the
rocks over which the ice moves, creating
sediment that glaciers carry away.
• When a glacier melts, it deposits the
sediment it carried.
Ice (cont.)
glacier
from Greek glacies, means “ice”
Much of North America was covered by ice
20,000 years ago,
Ice (cont.)
• The processes that move Earth material
depend on climate, or the average
weather in a region over a long period of
time.
• The processes that change the features
made by plate movement are affected by
plate movement itself.
Ice (cont.)
How do water, ice, and wind
change Earth’s surface?
• Physical weathering breaks down
rocks into smaller pieces but does
not change the mineral composition.
• Chemical weathering changes a
rock’s mineral composition. This
makes rocks weaker and helps break
down rocks into smaller pieces.
• Gravity, wind, water, and ice can
cause physical and chemical
weathering. They break down, erode,
transport, and deposit rocks and
sediment.
Which term refers to the process
of changing the composition of
rocks?
A. deposition
B. mass wasting
C. chemical weathering
D. physical weathering
Which is the laying down, or
settling, of eroded material?
A. deposition
B. mass wasting
C. chemical weathering
D. physical weathering
Which is the moving of weathered
material, or sediment, from one
location to another?
A. deposition
B. erosion
C. mass wasting
D. weathering
Do you agree or disagree?
5. Wind erosion only occurs in the desert.
6. Rivers are the only cause of erosion.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Interaction of tectonic
plates at plate
boundaries forms
earthquakes,
volcanoes, and
mountains. Erosion
and deposition by
water, wind, and ice,
along with mass
wasting, can change
the landforms made
by plate motion.
Lesson 1: Earth’s Moving Surface
• The theory of plate tectonics states that Earth’s
surface is broken into rigid plates that move with
respect to each other. Tectonic plates are pieces
of the lithosphere.
• At a convergent boundary, plates come together.
At a divergent boundary, they move apart. At a
transform boundary, plates slide past each other.
• Convection in
Earth’s mantle
causes tectonic
plates to move.
Lesson 2: Shaping Earth’s Surface
• Earthquakes occur a faults. Most
faults are near plate boundaries.
• Deformation near plate boundaries
forms volcanoes and mountain
ranges and causes earthquakes.
• Volcanoes form at convergent plate
boundaries on the plate that does
not get subducted. Lava also erupts at divergent
plate boundaries.
• At convergent boundaries, mountains form as a
result of repeated vertical movement on faults.
Lesson 3: Changing Earth’s Surface
• Physical weathering changes the size of sediment
but does not change the composition of minerals.
• Chemical weathering dissolves minerals or changes
their composition.
• Gravity, water, ice, and wind erode landscapes and
move materials from one place and deposit them in
others.
Which includes the Earth’s crust
and uppermost part of the
mantle?
A. asthenosphere
B. lithosphere
C. convergent boundary
D. divergent boundary
Which occurs when one tectonic
plate moves under another
tectonic plate?
A. convection
B. plate tectonics
C. relative motion
D. subduction
Which is a crack, or fracture, in
Earth’s crust?
A. earthquake
B. fault
C. mid-ocean ridge
D. volcano
Which is created by lava
spreading over large areas of
Earth’s surface?
A. explosive eruption
B. lava flow
C. magma
D. mid-ocean ridge
Which term describes the
mechanical and chemical
processes that change Earth’s
surface over time?
A. weathering
B. mass wasting
C. erosion
D. deposition
Which boundary is between two
plates moving away from each
other?
A. convergent
B. divergent
C. lithosphere
D. transform
Which is the circulation within
fluids caused by differences in
density and thermal energy?
A. convection
B. plate tectonics
C. relative motion
D. subduction
Which term refers to magma that
erupts onto Earth’s surface?
A. volcano
B. mid-ocean ridge
C. lava
D. fault
Which term describes vents in
Earth’s crust through which
molten rock flows?
A. earthquake
B. fault
C. mid-ocean ridge
D. volcano
What term refers to large masses
of ice that move slowly across
Earth’s surface?
A. glaciers
B. landslides
C. lava flows
D. sediment