Weathering+and+Erosion

Weathering and Erosion

Weathering The Breakdown of rock at or near the surface of the Earth Physical Weathering

The Breakdown of rock into smaller pieces without chemical change.

Ice Wedging (Frost Action)

Water Held in the cracks of rock wedges the rock apart when it freezes Root wedging (Plant Action) Tiny roots grow into cracks in the rock and then as the root grows the rock splits

Exfoliation When large masses of rock, mainly igneous, are lifted up to the surface the relief of overlying pressure causes the rock to expand. Upward expansion leads to curved breaks which may peel off in layers.

Chemical Weathering The Breakdown of rock through a change in mineral or chemical composition



Oxidation The chemical reaction of oxygen with other substances. Iron is most easily attacked resulting in Rust (Iron Oxides)

Carbonic Acid When carbon Dioxide dissolves into water. It Dissolves many common minerals.

Minerals Resistance to Weathering

Different Minerals and rocks have different physical and chemical properties which allow them to weather at different rates.

Quartz Almost unchanged by chemical weathering. It is hard and does not have cleavage so it also resists mechanical weathering. Feldspar, Mica, Calcite, and Gypsum Affected by both types of weathering and will break down into clay with calcite and Gypsum dissolving and being carried off in solution.

Sedimentary Rocks Shale- Is the least resistant to mechanical weathering.

Sandstone- Is most resistant to mechanical weathering The type of cement which holds the sandstone together determines how resistant the rock is Calcite- Low resistance Silica- High resistance

Rocks which contain the mineral Calcite, such as Limestone or Marble, are somewhat resistant to mechanical weathering but is the least resistant to chemical weathering.

Factors Affecting rate of weathering Exposure The closer to the surface of the Earth, the faster it will weather - Rate and type of weathering depends on exposure of rocks to air, water and the action of living things.

SURFACE AREA

The greater the surface area exposed to weathering the faster the rate of weathering


 * Two examples of the same material having the same mass can have different surface areas. If one sample is a large piece of marble with a mass of 50g.

Climate Weathering is usually Greater in warm,Moist climates

Physical weathering is usually greater in MOIST areas with TEMPERATURE VARIATIONS (cold and warm)

SOILS Soil is made of loose, weathering rock and organic material in which plants with roots can grow. The rock material is composed of sand, silt, and clay.

Parent material is the material from which a soil is formed

Residual Soil- Soil that has bedrock beneath the soil as a parent material.

Transported Soil- Soils formed from deposits left by winds, rivers, and Glaciers.

Parent Material is the material from which a soil is formed Residual soil-Soil that has the Bedrock beneath the soil as a parent material.

Transported soil- Soils formed from deposits left by winds, rivers.

A-Horizon Topsoil Darkest color due to organic material

B-Horizon Subsoil 1.) Clay is washed to the subsoil 2.) May contain soluble minerals, such as calcium and magnesium carbonates 3.) Color is usually red-brown from iron oxides that form above and wash down

C-Horizon Made of slightly weathered parent material (rock fragments) Un weathered Bedrock

Climate Tropical soils form in areas with high temperatures and heavy rainfall. A thick infertile soil profile are results of heavy rain.

Grassland soils form in areas with enough rainfall for heavy grass, but not trees. About 1 meter thick and fertile.

Forest soils form in Humid regions with cool seasons. Soil profile is less then 1 meter thick with well developed A,B and C Horizons

Desert soils

Mass Movements Movements of loose earth material down a slope. A.)** **Gravity is an aid in weathering and erosion. Steep slopes weather to Gentle slopes. Creep- Slow, Imperceptible down slope movement of the soil. Causes objects that are fixed in the soil to lean downhill. Water i the soil is what adds the weight. Mudflow- The rapid movement

Slump- Occurs when a section of land moves downhill as a whole because of a plane of weakness in the underlaying soil.

Landslide- sudden movement of a mass of bedrock or loose rock down the slope of a hill or mountain. (avalanche - snow, ice, rock and soil) Talus- Is a pile of rock fragments at the base of a cliff.

Wind erosion wind transports materials by causing their particles to move in different ways. Suspension- a method of transport by which strong winds cause small particles to stay airbourne for long distances.

Saltaion- cause a bouncing of motion of larger particles. Saltation accounts for sand transport by wind.

wind erosion is greatest in arid climates (low precipitation) with little vegetation. (desert and sea shores)**


 * Abrasion is a process of erosion found in wind,water, and ice. It occurs when particles such as sand rub up against the surface of rocks or other materials.

Ventifacts are rocks shaped by windblown sediments.

wind depositation occurs in areas where wind velocity decreases.

Dunes are piles of windblown sand that have a gentle side and a steep side.

The gentler slope occurs when the side on which the wind is blowing (windward side). The steeper slop occurs on the side protected from the wind (leeward side) Loess- thick deposits of fine lightweight particles (silt,clay) that are carried by the wind in great quantities of long distances. they are some of the most fertile soils.

Louis Agassiz is known for the idea that Glaciers once covered many parts of the world.

Formation of a Glacier Glaciers are accumulations of ice large enough to survive summer melt-forms from snow under pressure which turns to ice.

Snow line- the lowest level that permanent snows reach in summer. Highest near the equator Firn is granular ice material formed in snow fields freshly fallen snow becoming compressed and re crystallizing.

The lower layers become ice and begin flowing downward or outward because. Alpine Glaciers (Valley glaciers) Occur in mountain regions above the snow line Flow downhill and carve out U-shaped valleys

Continental Glaciers (Ice Sheets) A glacier that spreads over a wide geographic area. FORM IN POLAR AREAS WHERE THE SNOW LINE IS CLOSE TO SEA LEVEL AND WIDE AREAS ARE ABOVE THE SNOW LINE. (responsible for much of the landscape in NY) 20,000 years ago, New York State was covered by a huge ice sheet that originated in Canada.

Glacier Movement The overlaying weight of snow and ice causes grains of ice to partially melt and refreeze. As this happens ice grains slip past each other and move downhill. Glaciers move more rapidly at the surface than at the base and faster at the center than at the sides. friction with the valley walls slow the flow.


 * Flow at a rate of a few.

Crevasses are cracks across the width of the Glacier that form when Glaciers move over steep slopes. ICE FRONT is end of a Glacier The Ice Front is STATIONARY as long as the rate of movement and melting are equal.

A Glacier RECEDES when it melts faster than normal.

A Glacier ADVANCES when the rate of movements is greater then the rate at which it melts.

pieces of rock are picked up as Glaciers move and then are dragged along the bedrock and/or valley wall. Fine sand acts as sandpaper and polish the bedrock.

Larger sediments leave long parallel scratches called STRIATIONS The finger lakes of NY were formed as advancing ice deeply scoured out valleys. Glacial trough are formed when a Glacier carve out a valley forming a U-Shaped Valley. Valley Glaciers leave sharp mountain tops while continental Glaciers leave rounded tops.
 * Striations show the direction the Glacier is moving.
 * Calving is when blocks of ice break off into the sea.

Here are a few Depositional features of Glaciers.. Moraine is a glacial deposit of unsorted rock material. Ground Moraine- Carried along the bottom

Lateral Moraine- Long lines of rock pieces along the valley sides

Medial Moraine**

Movements of loose earth material down a slope. A.) Gravity is an aid in weathering and erosion. Steep slopes weather to Gentle slopes. Creep- Slow, Imperceptible down slope movement of the soil. Causes objects that are fixed in the soil to lean downhill. Water i the soil is what adds the weight. Mudflow- The rapid movement

Slump - Occurs when a section of land moves downhill as a whole because of a plane of weakness in the underlaying soil.

Landslide- sudden movement of a mass of bedrock or loose rock down the slope of a hill or mountain. (avalanche - snow, ice, rock and soil) Talus- Is a pile of rock fragments at the base of a cliff.

Wind erosion wind transports materials by causing their particles to move in different ways. Suspension- a method of transport by which strong winds cause small particles to stay airbourne for long distances.

Saltaion- cause a bouncing of motion of larger particles. Saltation accounts for sand transport by wind.

wind erosion is greatest in arid climates (low precipitation) with little vegetation. (desert and sea shores)
 * [[image:http://gatosimages.com/images/wind%20erosion%20at%20bryce.jpg width="537" height="357"]]
 * Abrasion is a process of erosion found in wind,water, and ice. It occurs when particles such as sand rub up against the surface of rocks or other materials.

Ventifacts are rocks shaped by windblown sediments.

wind depositation occurs in areas where wind velocity decreases.

Dunes are piles of windblown sand that have a gentle side and a steep side.

The gentler slope occurs when the side on which the wind is blowing (windward side). The steeper slop occurs on the side protected from the wind (leeward side) Loess- thick deposits of fine lightweight particles (silt,clay) that are carried by the wind in great quantities of long distances. they are some of the most fertile soils.

Louis Agassiz is known for the idea that Glaciers once covered many parts of the world.

Formation of a Glacier Glaciers are accumulations of ice large enough to survive summer melt-forms from snow under pressure which turns to ice.

Snow line- the lowest level that permanent snows reach in summer. Highest near the equator Firn is granular ice material formed in snow fields freshly fallen snow becoming compressed and re crystallizing.

The lower layers become ice and begin flowing downward or outward because. Alpine Glaciers (Valley glaciers) Occur in mountain regions above the snow line Flow downhill and carve out U-shaped valleys

Continental Glaciers (Ice Sheets) A glacier that spreads over a wide geographic area. FORM IN POLAR AREAS WHERE THE SNOW LINE IS CLOSE TO SEA LEVEL AND WIDE AREAS ARE ABOVE THE SNOW LINE. (responsible for much of the landscape in NY) 20,000 years ago, New York State was covered by a huge ice sheet that originated in Canada. Glacier Movement The overlaying weight of snow and ice causes grains of ice to partially melt and refreeze. As this happens ice grains slip past each other and move downhill. Glaciers move more rapidly at the surface than at the base and faster at the center than at the sides. friction with the valley walls slow the flow.


 * Flow at a rate of a few.

Crevasses are cracks across the width of the Glacier that form when Glaciers move over steep slopes. ICE FRONT is end of a Glacier The Ice Front is STATIONARY as long as the rate of movement and melting are equal.

A Glacier RECEDES when it melts faster than normal.

A Glacier ADVANCES when the rate of movements is greater then the rate at which it melts. pieces of rock are picked up as Glaciers move and then are dragged along the bedrock and/or valley wall. Fine sand acts as sandpaper and polish the bedrock.

Larger sediments leave long parallel scratches called STRIATIONS** Calving is when blocks of ice break off into the sea. The finger lakes of NY were formed as advancing ice deeply scoured out valleys. Glacial trough are formed when a Glacier carve out a valley forming a U-Shaped Valley. Valley Glaciers leave sharp mountain tops while continental Glaciers leave rounded tops.
 * Striations show the direction the Glacier is moving.

Here are a few Depositional features of Glaciers.. Moraine is a glacial deposit of unsorted rock material. Ground Moraine- Carried along the bottom

Lateral Moraine- Long lines of rock pieces along the valley sides

Medial Moraine

Arete- a sharp rugged mountain ridge, produced by glaciation.
 * Cirque- A half-open steep-sided hollow at the head of a valley or on amountainside, formed by glacial erosion.

Horn-

Col- A break in an arete(mountain pass)

Trancated Spur- A blunt-ended, sloping ridge which descends from the flank of a valley. Its abrupt termination is normally due to erosion by a glacier. Glaciers tend to follow straighter courses than rivers.

Tarn- A small lake at the base of a cirque.

Hanging Valley- a tributary valley whose mouth is set above the the floor of the main valley, usually as a result of differences in glacial erosion.

Crevasse- A fissure, or deep cleft, in glacial ice, the earth's surface.

Roches Moutonees- (resting sheep) an outcrop of bedrock which has become elongated. Sculpted by a glacier one side is smooth and the other is left rough.

Striations- Any of a number of scratches or parallel grooves on the surface of a rock, resulting from the action of moving ice, as of a glacier. **

__Erosion and Deposition__

 * Erosion is the process by which earth materials are moved by natural agents like water, wind, and ice.**

__Running Water__

 * Running water is the most effective agent of erosion.

The Sun is where running water gets its energy.

Rocks are weathered both chemically and Physically by running water.**

Physical

 * Abrasion is the term given to the use of sand, pebbles, and even boulders as cutting tools to grind away at the stream bed. During this process the "tools" themselves wear down.**

Chemical

 * The water dissolves soluble minerals

Rivers carry rock material in three ways

Solution- This is material that is dissolved from the bedrock. Most commonly found in solution are compounds of calcium and magnesium.

Suspension- When small rock particles, such as clay silt and fine sand, are kept from sinking by th turbulence of the stream. This gives the water a muddy look.

Bed Load- Sand, pebbles, and some boulders which move along the stream bed.

Carrying Power

Carrying power is indicated by both the total amount of sediment in a stream and by the size of the particles being moved.**


 * The stream discharge and speed will determine the carrying power of the stream.

Discharge is the volume of water flowing past a given point at a given time.

Speed is generally determined by the steepness, or gradient, of its bed.

A stream moving at high speed with discharge can carry much larger sediments then a slow moving stream. Example: Spring time snow melting and excessive rain.

The River Valley
 * Rivers tend to have a V-Shaped valley because they tend to flow at high speeds and dig into the stream bed.

Base Level is the lowest level a river can cut into its bed.

To form a permanent stream rain water must flow down a slope and dig deep enough to cut into the water table. This wearing away of the land to form a stream valley is called headward erosion.

A divide is an area of high land that separates one river valley from another.

On either side of a divide a river system may form.

Watershed is all of the land that drains into the river either directly or through its tributaries.

Waterfalls

Water flowing over a steep cliff will result in a waterfall. Waterfalls are not permanent structures.

Undermining is the erosional process occurring at the base of a waterfall. Here water carrying sediment plunges down and back into the stream bed and cliff below. This causes the rocks at the top of the falls.

River deposition DEPOSITION OCCURS when a stream either decreases in speed or discharge.

Generally the speed decreases when its slope decreases or its bed widens. the greatest loss of speed occurs when a river empties into a quiet body of water.

A decrease in discharge would occur if a river traveled through an area with low precipitation.

As rivers begin to decrease their slope they move slower and will begin to move side to side.

As the valley wall on either side is eroded the valley floor is widened.

A flood Plain is the widened valley floor area which will accumulate water during times of excess rain when the river floods.

Erosion and Deposition in a river

Meanders are broad curves in the river (each bend or turn)

Erosion is greatest on the outside of a meander where water is flowing the fastest. (cut bank)

Deposition is greater on the inside of the meander where the water flows slower. (fill bank)

Oxbow Lake- Meanders can only become so large before they break through into another meander. The river then deposits mud and silt along the end of the abandoned meander. They now separated meander becomes a lake.

Running Water Deposits Well-Sorted Particles

Vertical Sorting- When sediments are suddenly deposited into water. The particles separate by size with the largest on the bottom and smallest on top.

Horizontal Sorting- When rivers empty their sediments into quiet bodies of water. Particles are sorted by size with larger particles being found closer to the shore and smaller particles being carried out into the body of water to be deposited.

Delta- A fan shaped deposit of sediment at the mouth of a river.

__Glacier Vocabulary ( Depositional)__

 * Drift- material, as gravel, sand, or clay, transported and deposited by a glacier or by glacial meltwater.

Till- Glacial drift consisting of an unsorted mixture of clay, sand, gravel and boulders.

Moraine- 1. a ridge, mound, or irregular mass of unstratified glacial drift, chiefly boulders, gravel, sand, and clay. 2.**a deposit of such material left on the ground by a glacier.

Outwash Plain- a broad, sloping landform built of coalesced deposits of outwash.

Kame- a ridge or mound of stratified drift left by a retreating ice sheet.

Kettle- a deep, kettle-shaped depression in glacial drift.

Drumlin- a long, narrow or oval, smoothly rounded hill of unstratified glacial drift.

Rock Flour- finely ground rock material produced by the grinding action of a glacier on its bed.

Erratics- noting or pertaining to a boulder or the like carried by glacial ice and deposited some distance from its place of origin.  Esker- a serpentine ridge of gravelly and sandy drift, believed to have been formed by streams under or in glacial ice.

=__River Vocabulary Chapter 10__=

1. River Deposition- Rivers deposit their bed load when they slow down. This can occur in these ways:
 * Slope of land decreases
 * Stream channel widens
 * Stream empties into a lake or ocean

2. Permanent Stream- A **stream** that flows year-round because its bed lies below the water table, or because more water is supplied from upstream than can infiltrate the ground.

====3. Intermittent Stream-A watercourse that flows only at certain times of the year, conveying water from springs or surface sources; also, a watercourse that does not flow continuously, when water losses from evaporation or seepage exceed available stream flow. 4. Source- The __body__  of a stream where water begins to flow.====

====8. Drainage Basin or Watershed- is an extent of land where water from rain and melting snow or ice drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean. 9. Channel- the area of a valley occupied by running water. 10. Valley- Any low-lying land bounded by higher ground ( example: hudson valley) 11. Meanders-to proceed by or take a winding or indirect course: //The stream meandered through the valley.//  ==== 12. Flood plain- a nearly flat plain along the course of a stream or river that is naturally subject to flooding.

13. Delta- a level, fan shaped deposit formed at the mouth of a river where it flows into a quiet body of water. ( example: Mississippi river Delta in the Gulf of Mexico)

14. Alluvium- Deposits made by stream on flood plains or alluvial fans. Sediments are sorted by size.

15. Alluvial fans- a fan shaped deposits found at the base of a steep mountain where a stream suddenly slows down.

16. Alluvial cone- A steeper alluvial fan; forms in desert or semi-arid (desert) climate.

17. Oxbow Lake-a U -shaped piece of wood placed under and around the neck of an ox with its upper ends in the bar of the yoke.

18. Natural Levee- a deposit of sand or mud built up along, and sloping away from, either side of the flood plain of a river or stream.

19. Yazoo Stream- a tributary that flows parallel to the main stream for a considerable distance before joining it.

20. Lateral Sorting- As the velocity of a river decreases (slows down) along its course, boulders get deposited first, then cobbles, pebbles, sand, silt, and finally clay ( sorted by size over a distance)

21. Vertical Sorted- As the velocity of a river stops completely as it enters a pond, lake pr the ocean, sediments are sorted by size, shape and density in vertical layers.

22. Cut Bank- The outside bank of a river where erosion is occurring ( water flows fastest)

23. Fill Bank- The inside bank of a river where deposition occurs ( water flows slowly) 