Shaping Earth’s Surface

Shaping Earth’s Surface

Chapter 3, Lesson 5

What is weathering?

• Weathering is the process through which rocks or other materials are broken down.

Physical weathering

• Physical weathering: weathering caused by temperature changes, pushing, pulling, or rubbing.

• Plants and trees growing up between cracks in the street, or sidewalk. The pressure from their roots pushing against the rock will cause particles to break off.

• The breaking of material is a physical change.

Physical weathering

Physical weathering

• Gravity pulling rocks down a slope. The rocks bump into other rocks, causing chips, and cracks to form.

• Wind and water will pick up small particles of sand and dirt and rub it against exposed rock. Causing the surfaces of exposed rock to wear away.

Physical weathering

Rock slide

Water erosion

Chemical weathering

• Chemical weathering occurs when chemicals break down rocks.

• Chemical weathering in ground water break up underground rock, caves.

• Above ground, acid rain causes statues to tarnish, or metals to rust.

• Chemical weathering can also kill vegetation.

Chemical weathering

Erosion

• Erosion is the process through which weathered rock is moved from one place to another place.

• Land can be eroded in five different ways.–1. gravity–2. glaciers–3. running water–4. waves–5. wind

What is deposition

• Deposition: Particles of dirt and rock that are dropped off in another place.

• Deposition by water forms deltas at the mouth of a river.

Delta

What is Deposition by Waves

• Eventually, rivers flow into larger bodies of water, such as lakes or oceans. As a river enters a lake or an ocean, its speed slows. The river then deposits the rest of its sediment. This sediment builds up over time to form a delta.


• http://images.google.com/imgres?imgurl=http://www.greatdreams.com/weather/hurricane-ike11-gilchrist-tx.jpg&imgrefurl=http://www.greatdreams.com/weather/hurricanes-2008c.htm&usg=__Hy_2EL74SW9R9QH0iqHpEukDIQE=&h=1040&w=990&sz=396&hl=en&start=15&um=1&itbs=1&tbnid=dWa02EhClDAczM:&tbnh=150&tbnw=143&prev=/images%3Fq%3DHurricane%2Bin%2BBarrier%2BIslands%2BTexas%26um%3D1%26hl%3Den%26safe%3Dactive%26sa%3DN%26rls%3Dcom.microsoft:*%26tbs%3Disch:1


What is Deposition by Wind

• Wind can wear away at rocks, smoothing them out.

• Wind also can move sand or sediment from one place to another.

• When the winds slow down, the sand and soil are deposited.

• (Snow drifts in the plains during winter!)• (Sand dunes in the desert actually move!)



How are rivers changed?

• A river is changed by the erosion and deposition of sediment.

• Water can erode sediment as it flows through a river channel.

• As the water in the river or stream slows, the sediments are deposited along the shoreline.


• When water enters a river or steam faster than it is carried away, it is called a flood.

• Floods occur when water from a river or stream overflows its banks.

• Natural wetlands can soak up water and reduce the changes of a flood.

• A floodplain is an area that easily floods.


Flood control

• Floods are dangerous to people.• The force of moving water can wash away

trees, animals, cars, people, and even buildings.

• Floods leave mud, trash, and other debris in homes and on the streets.

Flood control

• Atlanta Flood – $250 Million

September 23, 2009ByJennifer Brett

Flood control

• A dam is a structure built across a river.• Water builds up behind the dam and is stored.• The water is released slowly over time to

prevent flooding.• Levees are walls built along the sides of a river.

• A levee raises the banks of a river so that

more water can flow through without flooding the surrounding area.

Flood control

Flood control

• In rural areas, plants help control floodwaters.• The roots of plants, along side a river or

stream, helps to hold soil in place, and can soak up floodwaters.

• Canals or channels can also be dug to carry away water that would cause floods.

Flood control

How are shorelines changed and protected?

• A shoreline or the edge of a body of water is changed by the erosion and deposition of sediment.

• Sediment is eroded and deposited along a shoreline by waves and wind.




• Waves: As waves wash sand off beaches, they deposit it in the water.

• Sandbar: a strip of sandy land that stretches for hundreds of kilometers along a coastline. (If above the water, Barrier Island.)

• Barrier Islands protect beaches from erosion.• http://

science.howstuffworks.com/barrier-island.htm

http://science.howstuffworks.com/barrier-island.htm




• Wind: Some coastal areas have one or more sets of dunes along the shoreline.

• Dunes protect areas farther inland from the large waves that can occur during storms.

• Dunes also shelter inland areas from the wind.


• Barricades, a breakwater is a long wall built out in the ocean parallel to the shore.

• Waves hit the breakwater and are slowed.• Slower waves cannot carry as much sand away

from the beach.


• Reclamation: Some beaches have been badly damaged and are in danger of being lost.

• Beach reclamation is a process where sand is brought from another place. The new wand “reclaims” the old shoreline.