topic 7 3 erosion - rhinebeck central school district · • glaciers • wind • waves copy....

EROSIONMr. Rocco

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Erosion:•The transportation(movement) of loose sediments produced by weathering

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AGENTS of EROSION:

• GRAVITY• Running water (streams)• Glaciers• Wind• Waves

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Gravity:1. mass movements rock

fragments2. Soil creepslow

downhill movement

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This is a diagram of creep. The hillside slowly slips over many years from

temperature or water.

3. Debris flow rapid flow of soil

4. Mud flow flow of fine particles (clay mixed with water)

5. Rock fall rapid falling of boulders

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This is a picture of a landslide. A type of mass wasting.

In this picture the land has slumped

into the road below.

HELP!!!..the Red Sox Bus

is Stuck!

This is a picture of an avalanche. It is similar to a landslide with ice

and snow instead of rock.

Streams:• Tributary: smaller streams

that flow into larger streams• Abrasion: large rocks rolling

along bottom of stream bed grind other rocks more smooth

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• Valley shape “V” shapedue to down cutting

• Watershed (Drainage basin): area of land drained by all local streams and rivers

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In this picture the running water eroded the sides of this canyon and created the V-shaped valleys.

RUNNING WATER

THE CHIEF

OF EROSION

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OBTAINS AND MOVES

SEDIMENTS 3 WAYS

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Stream Load:• material that a stream carries• Large pieces of rock pushing,

rolling, lifting along bed (hydraulic lift/saltation)

Smaller sediments (sand/pebbles) in suspension

• Very fine sediments (clay/IONS) dissolved in solution

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Stream Discharge:

• Volume of water passing a certain spot in a stream in a given amount of time (m3/ sec.) or (ft3/sec)

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Hydrologists measured stream discharge and took water samples to determine how much sediment is suspended in the stream and how much sediment is moving along the streambed.

Tuolumne River in Yosemite National Park.

Stream Velocity: 4 Factorsneeded to increase velocity

1. Gradient (slope) steep slope

2. Discharge high discharge

3. Channel shape semicircular4. Location in a Stream

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FAST

FAST

SLOW

SLOW

SLOW

FAST

FAST

FAST

FAST

FAST

SLOW

SLOW

SLOW

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Carrying Power:• the ability of a stream to

move particles of different sizes

• depends on velocity of stream

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GLACIERS

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Glaciers• Continental: covers large area of

land mass(North America)• Valley: higher mountain tops• Striations: scratches show

direction of glacial movement• Valley shape “U” shape

–Hudson Valley–Finger lakes of Central NY

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What if?• If all the ice in Antarctica

melted, sea level would rise about 200 feet and flood most major cites on Earth.

• 85 % of all glaciers are in Antarctica and 10% in Greenland

(Firn) (approx. 20 meters)

FASTEST PART

Glacier

Antarctica(Striations)

Top end of a Hanging Valley emptying into the main valley via a waterfall

THE FINGER LAKES WERE FORMED BY GLACIERS!

•Keuka, Seneca, Waneta, Lamoka, Cayuga, Pine andCanandaigua Lakes

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Effects of Glaciers

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Extent of glacial ice at the maximum extent of the most recent glacial advance (approx. 11,000 years ago)

Glacial Ice in North America

Small changes in the Earth’s orbit may produce dramatic changes in ice cover

British Columbia

Glacier National Park, Montana

Mt McKinley, Alaska

Juneau Icefield is located to the east of the capital of Alaska, Juneau. The Juneau Icefield is the fifth largest such area on the North American continent (approximately 2400 square kilometers) and estimated depths 75 to 720 meters. This photo shows many features common to glacial areas such as: arête, nunataks, cirques, medial and lateral moraines, crevasses, and arcuate structures responding to the geology below the ice (see links below for more details. The image above shows just a portion of one of the 38 glaciers that feeds the huge Icefield. Mendenhall Glacier, which exits the IceField north of Juneau and is an excellent example of a retreating glacier (estimated about 40m/year).

GLACIAL FEATURES• Moraine: unsorted(mixed) pile of

sediments dropped by a melting glacier• Most of Northern US and NY• Terminal moraine last stop of

advancing glacier(Long Island, NY)• Outwash plain: a body of deposits that forms a

broad plain beyond a moraine• Drumlin: streamlined hill

Steep slope points in direction glacier came from

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Formation of a moraine… the ice front remains stationary, and the ice continues to flow, creating a pile of materials.

DRUMLIN

ICE MOVEMENT

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Terminal Moraine

Arêtejagged, knife-edged ridge(Yosemite NP,CA)

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Crevasse cracks in the rock as a glacier moves

It’s A-Rod again….I’m stuck

again…HELP!

Awe..Leave’em

Mountain glacier

Boy…that was close!

UNSORTED TILL!(Moraine)

UNSORTED TILL!(Moraine)

ERRACTICS: boulders transported and scratched by glaciers!

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ERRATIC(North Dakota)

Glad I ate my Wheaties this

morning…how much farther?

ESKERMELT WATER FEATURECOPY

ESKER

HANGING GLACIER!

KAMEConical shaped hills of sand and

gravel (kames) represent features of stagnant ice.COPY

Satellite photos of Kettle Lakes blocks of ice left behind that melt

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KETTLE LAKES

Finger Lakes

Outwash plain small rivers that carry sediment out of glaciers forming a delta(South Shore of Long Island)(LAYERED AND SORTED) COPY

WIND Erosion

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Terms• Deflation: removal of clay,

silt, sand from ground• Dune: mound or ridge of

sand • Loess: wind-deposited silt,

fine sand, and clay

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CROSS-BEDDING

Mushroom Cap Rock!

SANDBLASTING

Properly designed strips are effective against wind erosion.Strip farming controlled soil drifting.

STRIP FARMING CANADA

• Strip farming is a method of farming used when a slope is too steep or too long, or when other types of farming may not prevent soil erosion. Strip farming alternates strips of closely sown crops such as hay, wheat, or other small grains with strips of row crops, such as corn, soybeans, cotton, or sugar beets. It is also known as strip cropping.

• Strip Farming helps to stop soil erosion by creating natural dams for water, helping to preserve the strength of the soil. Certain layers of plants will absorb minerals and water from the soil more effectively than others. When water reaches the weaker soil that lacks the minerals needed to make it stronger, it normally washes it away. When strips of soil are strong enough to slow down water from moving through them, the weaker soil can't wash away like it normally would. Because of this, farmland stays fertile much longer.

STRIP FARMINGMontana

Sand dunes in Death Valley, California .

These crescent dunes of coastal Peru are migrating toward the left

Ripples on a dune in Eureka Valley, California

Star dunes, such as these of the Namib, indicate the winds that formed them blew from many directions

WAVE ACTION

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Wave action is when waves hit the rocks and pieces of rock break off.

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A-Rod…are you ok?

Yeah…Boy that was a big wave! I scraped up my knee pretty bad,

though.

North Shore of Oahu, Hawaii, on October 1, 2006

Terms:• Jetties: rock walls that protect entrance of a

harbor from sediment deposition and waves• Longshore current: movement of sediment

parallel to shore as waves strike shore at an angle

• Barrier islands: sandbars that are above sea level

• Spit: finger-like sediment that extends out into open water

• Sandbar: sand parallel to shore underwater

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Jettie

Backwash

Jetties along Lake Ontario near Detroit, Michigan. Can you tell the direction of longshore drift?

Sea caves form when waves attack weak portions of a cliff. The pounding and cutting of the waves on the weak rock cause large holes to be cut from the cliff. Notice the small sea cave in the picture above

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Hey, Wilson….get over

here

Sea arches are formed when waves cut completely through a sea cave. This can form a natural arch or bridge.

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Sea arch - a feature of coastal erosion

AGENT/SEDIMENT CHARACTERISTICS

/WAVES

/WAVES

/WAVES

/WAVES

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