weathering+and+erosion

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 beling carried off in solution.

Sedimentary Rocks: __Shale__ is the least resistant to mechanical weathering. Sandstone: Is the most resistant to mechanical weathering The type of cement which holds the sandstone together determines how resistant the rock is Calcite- Low Resistance Silica- Hugh 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
 * 2 samples 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, and the other is 50g of many small pieces of marble. The smaller size pieaces will have the greater surface area.

Climate Effect on Weathering : Chemical 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, weathered 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 the bedrock beneath the soil as a parent material.

Transported Soil: Soils formed from deposits left by winds, rivers, and glaciers.

A-horizon topsoil DARKEST COLOR DUE TO ORGANIC MATERIAL B-horizon subsoil 1) CLAY IS WASHED OT 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) Non-weathered bedrock

http://www.enchantedlearning.com/geology/soil/

Soil Horizons and Classification Cimate: 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 meeter 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 form in very dry climates. Soil profile is a few centimeters thick and be very fertile when they are watered
 * Arctic soils form at high elevations and high latitudes. Poorly drained surfaces and the bottom layers are constantly frozen.

Mass Movements: Movements of loose earth material down a slope. Creep**- Slow, imperceptible down slope movement of the soil. Causes objects that are fixed in the soil to lean downhill. Water in the soil is what adds the weight.** Mudflow**- The rapid movement of a water saturated mass of soil.** Slump**-** **Occurs when a section of land moves downhill as a whole because of a plane of weakness in the underlying 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 o transport by which strong winds cause small particles to stay airborne for long distances Saltation- Causes a bouncing of motion of larger particles. Saltation accounts for most sand transport by wind
 * 1) **Gravity is an aid in weathering and erosion. Steep slopes weather to gentle slopes**

Wind erosion is greatest in arid climates (low precipitation) with a 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 material
 * Ventifacts** are rocks shaped by windblown sediments

Wind deposition occurs in areas where wind velocity decreases Dunes: are piles of windblown sand that have a gentile side and a steep side The gentler slope occurs when the side on which the wind is blowing (windward side). The steeper slope occurs on t he 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 from freshly fallen snow becoming compressed and recrystallizing. The lower layers become ice and begin flowing downward or outward because of overlying pressure.

//Alpine Glaciers// (valley glaciers) Occur in mountain regions above the snow line. Flow downhill and carve out U-shaped valley

//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 leven 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

The overlying 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 that at the base and faster at the center than at the sides. Friction with the valley walls slow the flow. U shaped valleys.8 Flow at a rate of a few cm to several meters per day

Crevasses: are cracks across the width of the glacier that form when glaciers move over steep slopes
 * Ice front is the 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 movement 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
 * Striations show the direction of movement


 * 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 valey forming a U-shaped valley
 * Valley glaciers leave sharp mountain tops while continental flaciers leave rounded tops

Moraine is a glacial deposit unsorted rock material Ground Moraine - Carried along the bottom Lateral Moraine- Long lines of rock pieces along the valley sides Medial Moraine - When two glaciers come together and there lateral moraines join together

Cirque: A relatively small body of ice, firn, and snow, occupying an armchair-shaped hollow in bedrock. It is generally wide in relation to its length. Arete: A sharp narrow ridge found in rugged mountains. Horn: When a mountain has cirques all around it, the //glaciers// may carve it into a tall Col: A break in an arete (mountain pass) Truncated Spur: Blunt-ended ridge of rock jutting from the side of a glacial trough, or valley. Tarn: A small lake at the base of a cirque Hanging Valley: A valley, the lower end of which opens high above a shore, usually caused by the rapid erosion of a cliff. Crevasse: A deep fissure 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: A series of ridges, furrows or linear marks, and are used in several ways
 * GLACIER VOCABULARY** (erosinal)

Drift: Material, as gravel, sand, or clay, transported and deposited by a glacier or by glacial meltwater. Till: Unstratified soil deposited by a glacier; consists of sand and clay and gravel and boulders mixed together
 * GLACIER VOCABULARY** (depositional)

Moraine:
 * 1) lateral: forms along the side of a glacier
 * 2) medial: merging lateral morainesof two glaciers form a moraine in the middle of the glacier
 * 3) ground: a melting glacier depposits till in a thin layer over a broad area
 * 4) recessional: deposits of till that form at the end of a glacier as it retreats
 * 5) terminal: the end moraine found at the farthest advance of a glacier

Outwash Plain: A sandur (plural sandar) is a glacial outwash plain formed of sediments deposited by meltwater at the terminus of a glacier. Kame: A round hill or short ridge of sand or gravel deposited by a melting glacier Kettle: A depression left in a mass of glacial drift, formed by the melting of an isolated block of glacial ice. Drumlin: A mound of glacial drift Rock Flour: Rock flour, or glacial flour, consists of clay-sized particles of rock, generated by glacial erosion or by artificial grinding to a similar size Erratics: Boulders carried long distances by the glaciers and deposited when the glacier melted. They tend to be smooth and rounded Esker: A long winding ridge of post glacial gravel and other sediment; deposited by melt water from glaciers or ice sheets

RUNNING WATER: is the most effective agent of erosion The sun is where running water gets its energy
 * Erosion** is the process by which earth materials are moved by natural agents like water, wind, and ice

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 the process the "tools" themselves wear down CHEMICAL: the water dissolves soluble mienrals

River carry rock material in 3 ways Solution: This is material that is dissolved from the bedrock. Most commonly found in solution are compounds of calcium and magnesium Suspension: When rock particles, such as clay silt and fine sandd, are kept from sinking by the movement of the stream. This gives the water a muddy look Bed Load: San, pebbles, and some boulders which move along the stream bed

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

The River Valley BASE LEVEL is the lowest level a river can cut into its bed - To form a permanent strea 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
 * Rivers tend to have a V-Shaped valley because they tend to flow at high speeds and dig into the stream bed

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 to overhang. Over time this overhang will collapse and the stream will move back towards its source.

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 widened valley floor area which will accumulate water during times of excess rain when the river floods

Erosion & 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. The bow 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

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, and stream, empties into a lake or ocean 2) 3) 4) 5) 6) 7) 8) 9) Channel: The area of a valley occupied by running water 10) Valley: Any low-lying land bounded by higher ground (ex. hudson valley) 11) Meanders: Curve or bend in a stream formed when a streams slope decreases, water builds up in the stream cahnnel, and moving water erodes away the sides of the stream bed 12) 13) Delta: A level, fan-shaped deposit formed at the mouth of a river where it flows into a quiet body of water. (ex. mississippi river delta in the gulf of mexico) 14) Alluvium: Deposits made by steams on flood plains or alluvial fans. Sediments are sorted by size 15) Alluvial fans: A fan-shaped deposit found at the base of a steep mountain where a stream sudedenly slows down 16) Alluvial Cone- A steeper alluvial fan; forms in desert or semi-arid (desert) climate 17) 18) 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 corse, boulders get deposited first, then cobbles, pebbles, sand. silt, and finally clay (sorted by size over a distance) 21) Vertican Sorting: As the velocity of a river stops completely as it enters a pond, lake or 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)