Earth Science - Erosion and Deposition

What is a glacier and how are they formed?

A glacier is a huge mass of ice that moves slowly over land. Glaciers are formed in areas where more snow falls than melts. The snow begins to compress, and it changes to hard, round ice pellets. More snow falls on this hardened ice and compresses it even more. It is now a hard, grainy ice called firn. As time passes, layers of firn pile on top of each other. Eventually, the layers of firn fuse together and form a solid glacier.

Summarize how a river develops.

A river develops by starting out as a stream running down a mountainside. Melted snow and ice and rainwater add to the stream. As the stream flows downhill, it flows through cracks and folds in the mountain. Eventually, multiple streams will join together creating a body of water big enough to be a river. As the river flows, it changes the landscape by weathering away rock and carving out valleys.

Compare the formation of features produced by wave erosion.

Bay - Sand is deposited at bays when wave energy is dispersed due to wave refraction. Wave-Cut Cliff - As waves crash into a cliff, the bottom part of the cliff is weathered and eroded away. This causes the top part of the cliff to eventually collapse, and the cliff face retreats. Wave-Cut Platform - When waves form a wave-cut cliff, a platform of rock forms where the face of the cliff once was. This platform of rock is a wave-cut platform. Arch - When waves erode through a cliff, it forms an arch. Sea Stacks - When an arch collapses, the towers that supported the arch remain. These towers are known as sea stacks.

Explain how beaches are formed.

Beaches are formed from the deposition of sediment at a shoreline. It starts with a base, usually the bedrock that composes the Earth in that area. Waves carry sediments to the base on the shoreline. These sediments build up over a long period of time and form the sandy beaches. The waves determine the shape of the beaches.

Explain the two types of stream deposition.

Delta - A stream slows to a stop when it enters standing water. Then, the water drops its sediments back and forth across the region, forming a wide triangular delta. Alluvial Fan - Developed when a stream falls down a steep slope onto a broad flat valley.

What is deposition?

Deposition is the process of sediments accumulating in new areas.

Explain how erosion affects the development of a river channel.

Erosion affects the development of a river channel because it can change the course of a river. When water carries sediments down the stream through saltation, the sediments hit the riverbed and sides of the river. This dislodges some of the sediments in the riverbed and causes them to flow downstream as well. Over time, the erosion of the riverbed and deposition of the sediments in other places could change the direction that the river flows altogether by blocking certain routes through deposition and opening up others through erosion.

What is erosion? How is it different from weathering?

Erosion is the overall process that results in movement of rocks and soil from one place on Earth's surface to another. It is different from weathering because weathering is wearing down and breaking of rocks. Erosion is facilitated by weathering.

What factors affect the rate of erosion and deposition? (Stream)

Factors that affect the rate of erosion and deposition are the steepness of a stream bed, rainfall, the amount of snow melting, speed of the stream, run-off from parking lots and fields, water releases from dams, removal of trees and shrubs, the volume of the water in the stream, and the amount of solid material carries by the river.

What factors affect the rate of erosion? (Wave)

Factors that affect the rate of erosion are rock type, wave size, wind strength, slope angle of the shore, weather conditions, vegetation amount, and human interference.

Explain how gravity contributes to erosion.

Gravity contributes to erosion by making water and ice move. It also causes mass movement, which is the movement of rock, soil, snow, or other material downhill.

Describe the features formed by glacial deposition.

Lateral and Medial Moraines - Formed from rock and debris transported by glaciers. Lateral moraines form on the sides of glaciers, and medial moraines form between two tributary glaciers. They mark the edges of a body of ice. Terminal and Recessional Moraines - Formed from rock and debris transported to the end of a glacier. They mark the end of a glacier. Glacial Till and Glacial Flour - Sediments produced from the grinding of glaciers against rock. Glacial till can be sediments of any size, while glacial flour is the smallest size of sediment. Glacial flour causes the milky color in glacier fed rivers, streams, and lakes. Glacial Erratics - Formed when a glacier picks up a large chunk of rock and drops it far from where it was picked up. Kettles - Sediment gets washed out from the glacier as it recedes. The sediments get deposited in a flat area below, forming an outwash plain. Kettles are depressions that form "scars" around these plains. Drumlins - Hills of sediment that have been streamlined by the movement of glaciers. Outwash Plains and Eskers - Formed from melted glacier water and contain glacial sediments. Outwash plains form in front of glacier ice, while eskers are formed beneath glacier ice.

Describe the parts of a river system.

River Source - Where the river starts. It can come from runoff, melted glaciers, or groundwater. Tributaries - Smaller streams that flow into a main river. Floodplain - Areas around the river that have the potential to flood during a storm. Meander - A curving area of a river. Confluence - The place where the tributary and main river meet. River - The main channel of a river system. Oxbow Lake - A meander that erodes the land so much that if cuts itself from the main river. This forms a lake in the shape of a bow. Levee - An artificial embankment made to keep the river from flooding. Channel - The path that a river or stream follows. Weathering and erosion can change this. Mouth - The place where the river flows into a bigger body of water, like an ocean. Delta - An underwater deposit of sediment at the mouth of the river into a lake or ocean. Estuary - A body of water where salt water meets freshwater.

What types of mass movement occur because of gravity?

Rockfalls - The abrupt movement and free fall of loosened blocks of solid rock. Creep - Very slow movement of soil particles and rock debris downhill. Bulging - The creep of rock material below Earth's surface. Landslides - Multiple downhill movements of bedrock and other debris caused by the separation of a slope section along a plane of least resistance or slip surface. Slump - A mass of rock or loosely consolidated materials moves a short distance down a hill or mountain. Earthflow - A downhill flow of fine-grained materials that have been soaked with water. It is faster than creep, but it is still slow. Mudflow - An earthflow that is moving faster with more water. Avalanche - A fast moving earthflow in a mountain region. Solifluction - The downhill movement of saturated material on the surface over a frozen material underneath it. This occurs in sub-Arctic areas while the land is thawing.

Describe the types of wind deposits.

Sand Dunes - Winds slow down, usually due to an obstacle. This causes the wind to drop its sand. The wind moves over the obstacle, which pushes the sand up the gently sloping side of the dune. When the wind passes over the dune, it slows down and causes sand to cascade down the crest. Loess - Winds blow silt and clay that deposit layer on layer over a large area. They form nearly vertical cliffs, and they form downwind of glacial outwashes or deserts. Wind can also deposit particles on the ocean surface. These particles sink to the bottom of the ocean and form fine-grained mud and clay.

What are the agents of erosion and deposition?

The agents of erosion and deposition are water, wind, ice, gravity, and occasionally lava flows and organisms.

What factors affect the rate of erosion and deposition? (Wind)

The factors that affect the rate of erosion and deposition are cloddiness, surface roughness, wind speed, soil moisture, field size, and vegetative cover.

What factors affect the rate of erosion and deposition? (Gravity)

The factors that affect the rate of erosion and deposition are erosional debris cover on slopes, the structure and character of rocks, the amount of vegetation on the hill, mountain, or other slope, the slope's steepness, any earthquakes, the presence of flowing groundwater, and the climate.

What factors affect the rate of erosion and deposition? (Glacier)

The factors that affect the rate of erosion and deposition are the type of glacier, thickness of ice, hardness of the rocks the glacier picks up, amount of rocks and debris picked up by the glacier, quantity of meltwater, strength of bedrock, and permeability of rock.

Describe the landscape features that are produced by glacial erosion.

U-Shaped Valleys, Fjords, and Hanging Valleys - Steep-walled, flat-bottomed valleys that glaciers carve in the landscape as they move. Cirques - Bowl-shaped, amphitheater-like depressions carved into mountains and valley sidewalls by glaciers. Nunataks, Aretes, and Horns - Form from glacier erosion in areas where multiple glaciers move in multiple directions. The land forms stark, rocky outcrops above the glaciers when they are there. When the glaciers move away, uniquely shaped features are left. Glacial Striations - As a glacier moves, it picks up pieces of rock and sediment in the ice. This causes the bottom to become very rough, and it scratches bedrock on Earth's surface as it moves. These scratches are glacial striations that can reveal the direction the glacier is moving. Paternoster Lakes - Lakes that form in a valley that formerly had a glacier. The glacier scoops out the basins for the lakes.

Describe wave erosion.

Wave erosion occurs when waves crash against cliffs or other areas that stick out into the water. The bending of waves, called refraction, either concentrates the energy of the wave or disperses it. When refraction concentrates wave energy and the wave crashes into a cliff or other land structure, pieces and sediments of the land structure are broken off. Over time, more sediments are eroded and the land structure gets smaller. In the case of a cliff, the erosion of the bottom of the cliff causes the entire cliff to collapse.

Describe how wind erodes land.

Wind erodes land by picking up particles and carrying them over long distances. The particles picked up by the wind hit other surfaces and cause them to break off as well.