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Title: Bellringer

Where does sand come from? Many people find the
sound of waves on a beach very relaxing and
peaceful. However, each wave that comes ashore
carries a certain amount of destructive force.
Write a short poem about how ocean waves create
sand from rock.
Wave Energy
  • When waves crash into rocks over long periods of
    time, the rocks are broken down into smaller and
    smaller pieces until they become sand.
  • Waves usually play a major role in building up
    and breaking down the shoreline. A shoreline is
    the boundary between land and a body of water.

Wave Energy, continued
  • As the wind moves across the ocean surface, it
    produces ripples called waves. The size of a wave
    depends on how hard the wind is blowing and how
    long the wind blows.
  • The wind that results from summer hurricanes and
    severe winter storms produces large waves that
    cause dramatic shoreline erosion.

Wave Energy, continued
  • Wave Trains Waves travel in groups called wave
    trains. When wave trains reach shallow water, the
    bottom of the wave drags against the sea floor,
    slowing the wave down.
  • The upper part of the wave moves more rapidly
    and grows taller, and begins to curl and break.
    These breaking waves are known as surf.
  • The time interval between breaking waves is
    called the wave period.

Wave Energy, continued
  • The Pounding Surf Tremendous energy is released
    when waves break. Crashing waves can break solid
    rock and throw broken rocks back against the
  • Breaking waves also wash away fine grains of
    sand, which are picked up by the waves and wear
    down and polish coastal rock.
  • The process continues until rock is broken down
    in smaller and smaller pieces that eventually
    become sand.

Wave Erosion
  • Shaping a Shoreline Wave erosion produces a
    variety of features along a shoreline. Much of
    the erosion responsible for coastal landforms
    takes place during storms.
  • Sea cliffs are formed when waves erode and
    undercut rock to produce steep slopes.
  • The next two slides show some of the major
    features that result from wave erosion.

Sea Arch
Sea Cave
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Wave-cut terrace
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Sea cliffs
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Wave Deposits
  • Beaches are areas of the shoreline made up of
    material deposited by waves. Some beach material
    is also deposited by rivers.
  • Waves carry a variety of materials, including
    sand, rock fragments, dead coral, and shells.
  • The colors and textures of beaches vary because
    the type of material found on a beach depends on
    its source.

Wave Deposits, continued
  • Wave Angle and Sand Movement Waves moving at an
    angle to the shoreline push water along the shore
    and create longshore currents.
  • Longshore currents move sand in a zigzag pattern
    along the beach.

Wave Deposits, continued
  • Offshore Deposits When waves erode material
    from the shoreline, longshore currents can
    transport and deposit the material offshore,
    which creates landforms in open water.
  • A sandbar is an underwater or exposed ridge of
    sand, gravel, or shell material.
  • A barrier spit is an exposed sandbar connected
    to the shoreline.

What causes wind? Why are some wind currents
stronger than others? Have you ever been near a
tornado or typhoon? A hurricane or straight-line
windstorm? What happened?   Write your answer in
your science journal.
The Process of Wind Erosion
  • Saltation is the skipping and bouncing movement
    of sand or other sediments, caused by wind or
  • Moving sand grains knock into one another,
    bounce up into the air, fall forward, and strike
    other sand grains, causing them to roll and
    bounce forward.

The Process of Wind Erosion, continued
  • Deflation is a form of wind erosion in which
    fine, dry soil particles are blown away, removing
    the top layer of fine sediment or soil and
    leaving behind rock fragments that are too heavy
    to be lifted by the wind.
  • Deflation may cause desert pavement, which is a
    surface consisting of pebbles and small broken
  • Scooped-out depressions in the landscape are
    called deflation hollows.

The Process of Wind Erosion, continued
  • Abrasion is the grinding and wearing away of
    rock surfaces through the mechanical action of
    other rock or sand particles.
  • Abrasion commonly happens in areas where there
    are strong winds, loose sand, and soft rocks.
  • The blowing of millions of sharp sand grains
    creates a sandblasting effect, helping erode,
    smooth, and polish rocks.

Wind-Deposited Materials
  • Loess is a deposit of windblown, fine-grained
  • Because wind can carry fine-grained material
    much higher and farther than it carries sand,
    loess deposits are sometimes found far from their

Chapter G3
Wind-Deposited Materials, continued
  • Dunes When the wind hits an obstacle, the wind
    slows down, depositing the heavier material. The
    material collects, creating an additional
    obstacle and eventually forming a mound that
    buries the original obstacle.
  • The mounds of wind-deposited sand are called
    dunes. A dune keep its shape, even though it

Wind-Deposited Materials, continued
  • The Movement of Dunes Different wind conditions
    produce dunes in various shapes and sizes. A dune
    usually has a gently sloped side and a steeply
    sloped side, called a slip face.

Fourteen thousand years ago, much of North
America was covered in a thick layer of ice
called a continental glacier, which moved as far
south as southern Illinois. Humans were living in
North America at the time. Write a paragraph
about being an early human and discovering this
GlaciersRivers of Ice
  • A glacier is a large mass of moving ice. They
    are capable of eroding, moving, and depositing
    large amounts of rock materials.
  • Glaciers form in areas so cold that snow stays
    on the ground year-round. Because glaciers are so
    massive, the pull of gravity causes them to flow
    slowly, like rivers of ice.

GlaciersRivers of Ice, continued
  • Alpine Glaciers form in mountainous areas. One
    common type of alpine glacier is a valley
  • Valley glaciers form in valleys originally
    created by stream erosion. As these glaciers
    slowly flow downhill, they widen and straighten
    the valleys into broad U shapes.

GlaciersRivers of Ice, continued
  • Continental Glaciers are huge, continuous masses
    of ice that can spread across entire continents.
  • The largest continental glacier in the world
    covers almost all of Antarctica. This ice sheet
    is approximately one and a half times the size of
    the United States, and is more than 4,000 m thick
    in some places.

GlaciersRivers of Ice, continued
  • Glaciers on the Move When enough ice builds up
    on a slope, the ice begins to move downhill.
    Thick glaciers move faster than thin glaciers,
    and the steeper the slope, the faster the
    glaciers will move.
  • Glaciers move in two ways sliding and flowing.
    A glacier slides when its weight causes the ice
    at the bottom to melt. A glacier flows as ice
    crystals within the glacier slip over each other.

Movement of Glaciers
Click below to watch the Visual
Concept. You may stop the video at any time
by pressing the Esc key.
Visual Concept
GlaciersRivers of Ice, continued
  • Glacier movement is affected by climate. As the
    Earth cools, glaciers grow. About 10,000 years
    ago, a continental glacier covered most of North

Landforms Carved by Glaciers
  • Continental glaciers and alpine glaciers produce
    landscapes that are very different from one
  • Continental glaciers smooth the landscape by
    scraping and eroding features that existed before
    the ice appeared.
  • Alpine glaciers carve out large amounts of rock
    material and create spectacular landforms.

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Types of Glacial Deposits
  • As a glacier melts, it drops all the material it
    is carrying. Glacial drift is the general term
    used to describe all material carried and
    deposited by glaciers.
  • Glacial drift is divided into two main types,
    till and stratified drift.

Types of Glacial Deposits, continued
  • Till Deposits Unsorted rock material that is
    deposited directly by the ice when it melts is
    called till. Unsorted means that the till is made
    up of rock material of different sizes.
  • The most common till deposits are moraines.
    Moraines generally form ridges along the edges of

Types of Glacial Deposits, continued
  • Stratified drift is a glacial deposit that has
    been sorted and layered by the action of streams
    or meltwater.
  • Streams carry sorted material and deposit it in
    front of the glacier in a broad area called an
    outwash plain.
  • Sometimes, a block of ice is left in an outwash
    plain when a glacier retreats. As the ice melts,
    sediment builds up around the block of ice,
    forming a depression called a kettle.

Glacial Drift Stratified Drift and Till
Click below to watch the Visual
Concept. You may stop the video at any time
by pressing the Esc key.
Visual Concept
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Watch for falling rock! Where would a warning
sign like this be necessary? Have you ever seen
one of these signs on a highway or trail? What
factors contribute to making a rock-fall zone?
Angle of Repose
  • Gravity is an agent of erosion and deposition.
    It influences the movement of water and ice, and
    it causes rocks and soil to move downslope.
  • Mass movement is the movement of any material,
    such as rock, soil, or snow, downslope.

Angle of Repose, continued
  • Material such as rock, soil, or snow moves
    downhill until the slope becomes stable. The
    angle of repose is the steepest angle at which
    loose material will not slide downslope.
  • The angle of repose is different for different
    surface material. Size, weight, shape, and
    moisture level determine at what angle material
    will move down-slope.

Rapid Mass Movement
  • Rock falls happen when loose rocks fall down a
    steep slope. The rocks can range in size from
    small fragments to large boulders.
  • Mass movements, like rock falls, happen suddenly
    and rapidly, and can be very dangerous.

Rapid Mass Movement, continued
  • Landslides are sudden and rapid movements of a
    large amount of material downslope.
  • The most common type of landslide is a slump.
    Slumping occurs when a block of land becomes
    detached and slides downhill.

Rapid Mass Movement, continued
  • Mudflows are rapid movements of large masses of
    mud. Mudflows happen when a large amount of water
    mixes with soil and rock. The water causes the
    slippery mass of mud to flow rapidly downslope.
  • Mudflows commonly happen in mountainous regions
    when a long dry season is followed by heavy rains.

Rapid Mass Movement, continued
  • Lahars are mudflows caused by volcanic eruptions
    or heavy rains on volcanic ash. Lahars can travel
    at speeds grater than 80 km/h and can be as thick
    as cement.
  • On volcanoes with snowy peaks, an eruption can
    suddenly melt a great amount of ice. Water from
    the ice liquefies the soil and volcanic ash to
    produce a hot mudflow that rushes downslope.

Slow Mass Movement
  • Creep is the slow mass movement of material
  • Although rapid mass movements are visible and
    dramatic, slow mass movements happen a little at
    a time. However, slow mass movements occur more
    frequently, and more material is moved

Click below to watch the Visual
Concept. You may stop the video at any time
by pressing the Esc key.
Visual Concept
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