Chapter 3- Erosion and Deposition
Terms in this set (81)
What is erosion?
The process by which natural forces move weathered rock and soil from one place to another.
What is sediment?
The material moved by erosion.
What is deposition?
Occurs where the agents of erosion, deposit, or lay down, sediment.
How can erosion, weathering, and deposition changes Earth's surfaces?
They act together in a cycle that wears down and builds up Earth's surface.
What is gravity?
The force that moves rock and other materials downhill.
What is mass movement?
Any one of several processes that move sediment downhill.
What are the four different types of mass movement?
Landslides, mudflows, slump, and creep
What are landslides? Give an example of why a landslide occurs.
When rock and soil slide quickly down a steep slope. May occur where road builders have cut highways through mountains or hills.
What is a mudflow? When do they often occur?
A rapid, downhill movement of a mixture of water, rock, and soil. Often occur after heavy rainfall.
What is a slump? When do they often occur?
A mass of rock and soil that suddenly slips down a slope. Often occurs when water soaks the bottom of soil that is rich and dry.
What does it mean when the rock and soil creep? What is the cause of a creep?
A creep is the slow, downhill movement of rock and soil. Results from he freezing and thawing of water in cracked layers of rock beneath the soil.
What is the major cause of erosion?
The major cause of erosion is moving water
What is runoff?
Water that moves over the Earth's surface
What are the five factors that affect runoff?
Amount of rain an area receives, vegetation, type of soil, shape of the land, and how people use the land.
Why do deserts have a high amount of runoff and erosion when they don't have rainfall?
They have few plants to hold the soil in place.
What are rills?
Tiny grooves in the soil caused by runoff traveling
What is a gully?
A large groove, or channel, in the soil that carries runoff.
What is a stream?
A channel along which water is continually flowing down a slope.
What is a tributary?
A stream or river that flows into a larger river.
What are the five features created through erosion by a river?
Valleys, waterfalls, flood plains, meanders, and oxbow lakes.
What are waterfalls?
Where a river flows over rock and flows over softer rock downstream.
What is a flood plain?
The wide, flat area of land along a river.
What is a meander? Over time what happens to the meander?
A loop-like bend in the course of a river. Over time, a meander erodes more of the outer bank and becomes more curved, eventually forming an oxbow lake.
What is an oxbow lake? How is it created?
A meander that has been cut off from a river. When a meander becomes very curved, the river can run straight through it and cuts off the curve, creating an oxbow.
What are two features that deposition creates?
Alluvial fans and deltas
What is an alluvial fan? Describe how it is created.
A wide, sloping deposit pf sediment, formed where a stream leaves a mountain range.
What is a delta? Describe how it is created.
Sediment deposited where a river flows into an ocean or lake and builds up a land form.
How is soil added to a river's flood plain?
Heavy rains or melting snow cause a river to rise above its banks and spread out over a flood plain. When the flood water retreats, it deposits sediment as new soil.
What is groundwater?
Underground water that trickled through openings in soil or cracks in rock.
How does groundwater cause erosion?
Through the process of chemical weathering
What is chemical weathering?
Water that sinks into the ground combines with carbon dioxide to form carbonic acid, which can break down limestone.
What is a stalactite?
A deposit that hangs from the roof of a cave
What is a stalagmite?
Slow dripping which forms cone-shapes from the cave floor
Describe how the process of deposition creates stalactites and stalagmites.
Water containing carbonic acid and calcium drips from the cave. Carbon dioxide is released from the solution, leaving behind a deposit of calcite.
What is kasrt topography?
When there is a layer of limestone near the surface in which groundwater erosion can significantly change the shape of the land.
What is energy?
The ability to do work
What is potential energy?
Energy that is stored to use later
What is kinetic energy?
Energy an object has due to its motion
How does water cause erosion?
As gravity pulls water down a slope, the water's potential energy changes to kinetic energy to do work.
What happens to most of the sediment in a mass movement?
It washes or falls into a river as a result of mass movement or runoff, or it erodes from the bottom or sides of a river
What is abrasion? What are examples of abrasion?
The wearing away of rock by a grinding action, like a boulder becoming smaller as it moves downstream.
What is load?
The amount of sediment a river carries
What are the factors that cause erosion and carry sediment?
A river's slope, volume of flow, and shape of a stream bed.
What happens to the load carried by a fast moving river? A slow moving river?
A fast-flowing river carries more and larger particles then a slow moving one. When a river slows down, it drops its sediment load.
If a river's speed increases, what is the effect of the sediment load and power?
It's sediment load will increase.
How does the volume of flow affect the speed of the river?
As more water flows through a river, its speed increases.
How does the volume of a river affect the land around it?
The river cuts more deeply into its banks and bed.
What is friction?
The force that opposes the motion of one surface as it moves across another surface.
How does friction affect a river's speed?
Reduced friction allows a river to flow faster, because less water comes in contact with the stream bed.
What is turbulence?
The movement of water in many ways.
How do friction and turbulence affect a river's flow?
They slow a stream's flow.
What are other factors that affect erosion and deposition?
What shape a river flows in (straight or curved)
What is a glacier?
Any large mass of ice that moves slowly over land.
What are the two kinds of glaciers?
Continental and valley glaciers
What is a continental glacier? Where are they found? How do they flow?
A glacier that covers a large area of an island or a continent. They are found in Antarctica and Greenland. They can flow in all directions.
What are ice ages? When did one occur?
When continental glaciers covered the Earth's surface. About 2.5 million years ago.
What is a valley glacier? Where are they found?
A long, narrow glacier that forms when snow and ice build up high in a mountain valley.
What is a requirement for a glacier to form? What happens when they reach more than 30 to 40 meters in height?
Can only form in an area where snow falls faster then it melts. Gravity begins to pull the glacier downhill when it gets too big.
What are the two processes by which glaciers erode?
Plucking and abrasion
What is plucking?
When a glacier flows over land and picks up rocks.
What does a glacier create after it has melted?
It deposits the sediment it eroded from the land and creates landforms.
What is a till?
The mixture of sediments that a glacier deposits directly on the surface.
What is a moraine?
The till deposited at the edges of a glacier
What is a kettle?
A small depression that froms when a chunk of ice is left in glacial till.
Where does the energy in waves come from?
From wind that blows across the water's surface
How do waves cause erosion?
Waves shape the coast through erosion by breaking down rock and transporting sand.
What is a headland?
Part of the shore that sticks out into the ocean.
What are landforms that are created by wave erosion?
Wave-cut cliffs, sea caves, sea arches, headlands, and sea stacks.
What coastal shapes are created by wave deposits?
Beaches, spits, and barrier beaches.
How is a beach created?
When waves drop the sediment they carry, forming a beach.
What is a longshore drift?
When waves repeatedly hit the beach and some sediment moves down the beach.
What is a spit?
A beach that projects like a finger into the water.
How does incoming waves affect sandbars and barrier beaches?
Incoming waves may build up sandbars or barrier beaches.
What is a sand dune?
A deposit of wind-blown sand
What are the two ways in which wind causes erosion?
Wind causes erosion by deflation and abrasion.
What is deflation? If you have a stronger wind, what is the result?
The process by which wind removes surface materials. The stronger the wind, the larger the particles.
What was the effect of deflation in the 1930's over parts of the Great Plains?
It caused the loss of about 1 meter of topsoil.
What is abrasion?
Abrasion by wind-carried sand that can polish rock.
What is wind deposition? What are the items created by wind deposition?
Its when sediment picked up by the wind falls to the surface. Forms sand dunes or loess deposits.
How are sand dunes created?
Sand shifts little by little in the wind.
What are loess deposits? Where are many loess deposits found?
Fine, wind-deposited sediment deposits. Many are found in central China and states like Nebraska, South Dakota, and Illinois.