Earth’s Changing Surface

Erosion – the process of moving weathered rock and soil from one place to another.

Sediment – the material MOVED by erosion.

Deposition – the dropping (depositing) of sediments as energy of motion decreases.

What is a CYCLE?› A process that repeats itself.

3 processes are constantly working on earth. As one area on earth is WEATHERED (broken

down), ERODED (carried away), sediments are DEPOSITED in another area (built up!)

Constantly changing the shape of the Earth.

Agents (the thing) that erodes the surface of the earth:

› Gravity› Running Water› Wind › Ice› Waves

Which “agent” is the most effective at erosion? › RUNNING WATER – is the major agent shaping the

surface of the Earth. Found everywhere.

Gravity – the force that moves rock and other materials DOWNHILL

Causes MASS MOVEMENTS – processes that move sediments downhill. Some types are fast, others are slow.

4 types

› Rockslides/Landslides› Mudslides› Slump› Creep

Most destructive › Rock and soil slide

QUICKLY down a slope

Common in mountainous areas, usually occur after heavy rains or earthquakes.

Forms TALUS SLOPES at bottom (pile of rocks)

Notice the scale – the size of the men to the size of the rocks

Water with sediments, gravity causes the mixture to slide downhill.

Occurs in DRY AREAS AFTER heavy rains.

Enough energy and mass to destroy things in path (houses, etc.)

Deposits at bottom of hill are usually cone-shaped.

                                 

Rock and soil suddenly slips down a slope. Does not travel far.

Moves in ONE LARGE MASS! (different than landslide/rockslide)

Looks as if someone pulled the bottom out!

Sediments slowly move downhill

Often caused by freeze-thaw action.

Happens over several years.

Evidence of creep by leaning utility poles, fences, tree trunks.

The most influential force in erosion is water.

Water’s ability to move materials from one location to another, along with the fact that it is found everywhere along the surface of the earth, makes it a superb tool for erosion.

Water erosion begins with a splash of rain

As water from rain moves over land it carries pieces of sediment with it – this water is called RUNOFF!

Water ALWAYS flows from higher to lower elevations, i.e., it flows downhill!

Rivers create:› Valleys and Canyons› Waterfalls› Floodplains› Meanders › Oxbow Lakes

Rivers often START on steep mountain slopes, pick up sediments from mass movements or from runoff.

Valleys (V-Shaped Valleys)› Near the source of a river, fast-flowing and

has a narrow straight course.

› Sediments along the side get carried away quickly

› Creates a deep, V-shaped valley

CANYONS› A narrow, deep, rocky, and steep-walled

valley carved by a swift-moving river.

› Its depth may be considerably greater than its width.

The Colorado River has eroded away the layers of sedimentary rock and formed the Grand Canyon.

http://www.youtube.com/watch?v=ktf73HNZZGY&feature=related

Grand Canyon Flyover http://www.youtube.com/watch?

v=h3jY4wzQPGs&feature=bf_prev&list=PL280EE176A94E121D&lf=results_video

Waterfalls› When water meets hard rock that is not

easily worn away, it continues to flow downstream to softer rock and wears the soft rock away!

DRAW THIS!

The “falls” are located near the center of town in Tinton Falls, near the mills and MJ’s pizza.

Flood plain› Flat land next to a river or a stream› As rivers flow along less steep land, they

spread out› During a flood, this is where all of the

excess water goes!

Meander› A loop—like bend in the course of a river› Sediments get pick up and dropped off

› The older a river is, the more erosion has occurred and the more and more curved it becomes

Glen Canyon is in Utah and Arizona

Oxbow Lake› A meander that has been cut off from the

river because of sediments

Draw this!

Moving water carries sediments and when the water slows down the sediments drop out and get “deposited”

Deposition BUILDS up new landforms

3 types:› Alluvial fans› Deltas› Flood plains

When a fast moving stream slows down (i.e., when it comes out of a mountain range)

Deposits sediments in the shape of a wide fan

The end of a river; when it flows into an ocean or a lake

The water is no longer moving downhill, slows down and sediment fall to the bottom.

The landform that is built up from these deposits is a DELTA

A and C are islands formed by the riverB is the Mississippi River deposits and D is the Mississippi Sound

Heavy rains or melting snow can cause rivers to rise over the edges of its bank and spread out over its “flood plain”

As the water recedes, sediments drop out

Makes fertile soil; good for crops.

Any large mass of ice that moves over land.› Valley glaciers – long, narrow snow and ice that

build up in valleys of mountains

› Continental glacier – a glacier that covers much of a continent or large island. Larger than valley glaciers

Form when snow build up year after year, pressure of the snow compresses the snow at the bottom into ice, and eventually gravity begin to pull it down the mountain.

Near Banff, Canada

Couloir and Hanging Valleys

MINI LAB

How do glaciers change the land?

Hold the ice with paper towels. Rub the ice, sand side down, over a bar of soap.

What happens to the surface of the soap?

Record your observations, wipe up your desks.

Return the soap to the paper plates.

Move slowly (centimeters to meters daily) Creates U-shaped valleys!

Valleys carved by glaciers – notice the U shape rather than an V shape!U-shaped valleys found in Alaska

Major force of erosion› Plucking

Picking up of rocks since they froze to the bottom of the glaciers

› Abrasion Dragging the rocks frozen to the bottom of the

glacier causes:

Striations – gauging and scratching of the bedrock

Striations in Canada

Rock in Central Park, New York

As a glacier retreats (or melts), it drops the sediments that it “plucked” up along the way – called “till”

Till – the mixture of sediments that a glacier drops on the surface

Moraine – the till deposited by the edges of a glacier› Terminal moraine – the till left behind at the

furthest location the glacier traveled.› Long Island, New York is a terminal moraine.

Terminal Moraine, Lateral Moraines and Till

Kettle Lakes› Glaciers drop chunks of ice in the till› Ice melts, fills the area with water – called

a kettle – if the water stays it forms a lake› Northwest NJ, Stokes State Park – hundreds

of Kettle lakes and ponds› The Great Lakes are kettle lakes

Erratic› Rocks dropped by glaciers – very different

in shape and type from “native” rocks› Some are quite large!

Tripod Rock on Pyramid Mountain

Wind, by itself is the weakest agent of erosion

In areas where few plants survive to hold soil in place (i.e., deserts, beaches) wind is powerful.

The main way that wind causes erosion is by DEFLATION and ABRASION!

Deflation – the process by which wind removes surface materials. Lifts dirt, blows it around, and drops it off somewhere else.

The stronger the wind, the larger the particle it can pick up and move.

All particles picked up by wind will eventually fall back down – may form DUNES.

Created on beaches and in deserts – when sand is dropped by wind – usually when the wind hits an obstacle.

Can be long and parallel, can be U-shaped, can be small or large and move over time.

Sand dunes constantly shift location with the wind, plants help to keep the dunes in place.

Formed in a U Shapes from the wind due to little vegetation!

Also called TRANSVERSE sand dune! The wind blows perpendicular to the dune!

Wearing away of rocks or beaches due to wave action

Creates:› Sea Caves Beach erosion› Sea Cliffs Spits› Sea Stacks Barrier Islands› Arches› Coves