Weathering+and+Erosion

= LINKS AT BOTTOM OF PAGE !! = Weathering! Weathering-** The breakdown of rocks at or near the surface of the earth. 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. - The type of cement which holds the sandstone together determines how resistance the rock is **Calcite- low resistance** and **Silica- high resistance. -**Rocks which contain the mineral calcite, such as //Limestone// or //Marble// are somewhat resistant to mechanical weathering but is the **least resistance to chemical 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. **Two 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 pieces will have the greater surface area. Climate effect on Weathering. Chemical weathering**- is usually greater in warm, moist climates.** Physical Weathering**- usually greater in moist areas with temperature variations (cold and warm)** **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** __**Climate**__ - Tropical soils form in areas with high temperatures and heavy rainfall. A thick infertile soil profile are results of heavy rain. - Grassland soil form in areas with enough rainfall for heavy grass, but not trees. About 1 meter thick and fertile - Forrest soils form in humid regions with cool seasons. Soil profile is less then 1 meter thick with well developed A, B, and C Horizons. - Deserts 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.
 * Physical Weathering**- the breakdown of rock into smaller pieces without chemical change.
 * Ice Wedging (frost action) - Water held in the cracks of rocks wedges the rock apart when it freezes.
 * 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 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 the most resistant to mechanical weathering
 * Factors Affecting Rate of Weathering! **
 * Surface Area- The greater surface area exposed to the weathering the faster the rate of weathering.
 * Soils**- soil is made of loose, weathered rock and organic material in which plants with root can grow. The rock material is composed sand, silt, and clay.
 * Parent material-** the material from which a soil is formed.
 * Residual Soil-** soil that has the bedrock beneath the soil as a parent material
 * Transported Soil-** soild formed from deposits left by winds, rivers, and glaciers.
 * A-Horizon (Top Soil)- darkest color due to organic material.
 * C-Horizon-** Made of slightly weathered parent material (rock fragments)
 * Unweathered Rock**

A) Gravity is an aid in weathering and erosion. Steep slopes weather to gentle slopes. **Wind Erosion- wind transports materials by causing their particles to move in different ** ways. Wind erosion is greatest in arid climates (low precipitation) with little vegetation (deserts and sea shores). Wind Deposition occurs in areas where wind and velocity decreases. The gentler slope occurs when the side on which the wind is blowing (windward side). The steeper slope occurs on the side protected from the wind (leeward side).
 * Mass Movement-** 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 fragment at the base of a cliff.
 * Suspension-** a method of 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.
 * Abrasion-** 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-** rocks shaped by windblown sediments.
 * Dunes-** are piles of windblown sand that have a gentle side and a steep slide.
 * 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 Firn- a granular ice material formed in snow fields from freshly fallen snow becoming compressed and re-crystallizing. The lower layers became ice and began flowing downward or outward because of overlying
 * Glaciers

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

****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.

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 than at the base and faster at the center than at the sides. Friction with the valley walls slow the flow. Crevasses- 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 is 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 than the rate at which it melts. Pieces if rock are picked up as glaciers move and then are dragged along bedrock and/or valley walls Fine sand acts as sandpaper and polish the bedrock Lager sediments leave long parallel scratched called striations Striations show the direction of movement Calving- when blocks of ice break off into the sea
 * Glacier Movement**
 * Flow at a rate of a few CM*

The Finger Lakes of NY were formed as advancing ice deeply scoured out valleys. Glacial through 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.

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- when two glaciers come together and there lateral moraines join together

Cirque- a bowl-shaped, steep-walled mountain basin carved by glaciation, often containing a small, round lake. Arete- a sharp rugged mountain ridge, produced by glaciation. Horn- one of the bony, permanent, hollow paired growths, often curved and pointed, that project from the upper part of the head of certain ungulate mammals, as cattle, sheep, goats, or antelopes Col- a break in an arete (mountain pass) Truncated Spur- occurs when spurs, formed in a mountainous area by river action, are truncated by the action of [|i]ce or active faulting. Tarn- a small lake at the base of a cirque Hanging Valley- a tributary valley with the floor at a higher relief than the main channel into which it flows. Crevasse- a fissure, or deep cleft, in glacial ice, the earth's surface, etc. Roches Mountonees- (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.
 * Glacier Vocabulary (Erosional)

**Glacier Vocabulary (Depositional) Drift-  driving movement or force; impulse; impetus; pressure. Till- unsorted glacial sediment Moraine- any glacially formed accumulation of unconsolidated glacial debris (soil and rock) which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past ice age. a) lateral- forms along the side of a glacier b) medial- merging lateral moraines of two glaciers form a moraine in the middle of the glacier c) ground- a melting glacier deposits till in a thin layer over a broad area d) recessional- deposits of till that form at the end of a glacier as it retreats e) terminal- the end moraine found at the farthest advance of a glacier Outwash Plain- formed of sediments deposited by meltwater at the terminus of a glacier. Kame- a geological feature, an irregularly shaped hill or mound composed of sand,gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier. Kettle- a shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters. Drumlin- a mound of glacial drift 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. Esker- a long winding ridge of stratified sand and gravel

__**Erosion and Deposition**__ Erosion is the process by which earth materials are moved by natural agents like water, wind, and ice. Running Water is the most effective agent of erosion. The sun is where running water gets it energy. ** Rocks are weathered both Chemically and Physically by running water Abrasion- 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 Solution-** This is material that is dissolved from the bedrock. Most commonly found in solution are compounds of calcium and magnesium. The stream discharge and speed will determine the carrying power of the stream. Speed-** ** is generally determined by the steepness, or gradient, of its bed. A stream moving at high speed with a high discharge can carry much larger sediments then a slow moving stream. Example: Spring time snow melting and excessive rain. ** Rivers tend to have a __V-shaped__ valley because they tend to flow at high speeds and dig into the stream 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. //**//**Divide-** an area high of land that separates one river valley from another. On either side of a divide a river system may form. // Generally the speed decreases when its slope decreases or its bed widens. The greatest loss of speed occurs when river empties into a quiet body of water. A decrease in charge 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. The //Flood Plain// is the widened valley floor area which will accumulate water during times of excess rain when the river floods. Meanders-** 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) Vertical Sorting**- When sediments are suddenly deposited into water. The particles separate by size with the largest on the bottom and smallest on top.
 * Running Water
 * Physical
 * Rivers carry rock material in three ways...
 * Suspension-** When small rock particles, such as a clay silt and fine sand, are kept from sinking by the 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-** indicated by both the total amount of sediment in a stream and by the size of the particles being moved.
 * Discharge- the volume of water flowing past a given point at a given time.
 * The River Valley**
 * //__Base Level__ - is the lowest level a river can cut into its bed.
 * Watershed-** 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.[[image:8eeeccce840c1630cac59a06ad2e72c7_3D_Waterfall_Screensaver.jpg caption="Waterfall"]]
 * Undermining-** the erosional process occurring at the base of a waterfall. Here water sediments 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.
 * Erosion and Deposition in a River
 * Oxbow Lake**- Meanders can only become so large before they break through into other meander. The river then deposits mud and silt along the end of the abandonded meander. The now separated meander becomes a lake.
 * Running Water Deposits Well-Sorted Particles
 * 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 deposits of sediment at the mouth of a river.

1. **River Deposition-** river deposit their bed lad when they slow down. This can occur in these ways: -slope of land decreases, -stream channel widens, or -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-** An intermittent stream has flowing water during certain times of the year, when groundwater provides water for stream flow. During dry periods, intermittent streams may not have flowing water. Runoff from rainfall is a supplemental source of water for stream flow. 4. **Source-** the start of a stream where water begins to flow 5. **Mouth- the end of a stream where it empties into another water body 6. Divide- an area of 7. Tributary-** any stream that connects water to another stream 8. **Drainage Basin or Watershed-** the highland separating one river basin from another. 9. **Channel-** an area of a valley occupied by running water 10. **Valley-** any low-lying land bound by higher ground (example: Hudson Valley) 11. **Meanders-** broad curves in the river (each bend or turn) 12. **Flood Plain-** the widened valley floor area which will accumulate water during times of excess rain when the river floods. 13. **Delta-** a level, fan- shaped deposits of sediment 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 streams on flood plains or alluvium fans. Sediments are sorted by size. 15. **Alluvial Fans**- a fan-shaped deposit found at the base of a steep mountain where a stream suddenly slows down. 16. **Alluvial Cone-** a steeper alluvial fan; forms in a desert or semi-arid (desert) climate. 17. **Oxbow Lake-** a crescent-shaped lake (often temporary) that is formed when a meander of a river is cut off from the main channel 18. **Natural Levee-** Low ridges of flood-deposited sediment formed on either side of a stream channel, which thin away from the channel. 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 distance) 21. Vertical Sorting- as the velocity of a river stops completely as ti enters a pond, lake or the ocean, sediments are sorted by size, shape and density in vertical layers. 22. Cut Bank- the outside of a river where erosion is occurring (water flows fastest) 23. Fill Bank-** t <span style="font-family: arial,sans-serif; font-size: small; line-height: normal;">he inside <span style="font-family: arial,sans-serif; font-size: small; line-height: normal;">of a river where deposition occurs (water flows slowly)
 * __River Vocabulary__**

__Links__
 * Weathering&Erosion Notes-** http://www.mrsciguy.com/weathering.html
 * Weathering&Erosion Quiz-** ** http://www.softschools.com/quizzes/science/weathering_and_erosion/quiz448.html **
 * Weathering&Erosion Notes-** http://qldscienceteachers.tripod.com/worksheets/junior/geology/
 * Waterfall Quiz-** http://www.livefortheoutdoors.com/News-Landing/Search-Results/Features/Waterfalls-Quiz/