nweathering and erosion

weathering


- The breakdown of rocks at or near the surface of the earth
- physical weathering
the breakdown of rock into smaller pieces without chemical change

ice wedging

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- water held in the crackes of rocks wedges the rock apart when it freezes
- root wedging (plant action)
- tiny roots grow into cracks in the rock and then as the roots grow then 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
chemical_weathering4jjpg.jpg
- 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 attacted 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 chemically weathering it is hard and does not have cleavage so it also resists mechanical weathering

feldspars. mica, calcite and gypsum
-affected b both types of and will break down into clay with calcite and gypsum dissolving and carried off in solution

sedimentary rocks
shale- is the least resistant to mechanical weathering

sandstone- in the most resistant to mechanical weathering

the type of cement which holds the sandstone together determines how resistante the rock is
calcite- low resistance
silica- high resistance

rocks that contain the mineral calcite such as limestone or marble are somewhat resistant to mechanical weathering but is the least resistant to chemical weathering

Factors that affect the 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 samples of teh 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 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- is usually greater in moist areas with temperature variations (cold and warm)

soils
animation of soil and types of it and layers use link below

http://www3.interscience.wiley.com:8100/legacy/college/strahler/0471238007/animations/ch21_animations/animation1.html

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 is the material that which the soil is formed
residual soil- soil that has the bedrock beneath the soil as a parent material
transported soil- soils formed from deposited left by winds, rivers, and glaciers

A-horizon topsoil
darkest color due to organic material

b-horizon
1- Clay is washed to the subsoil
2- may contain soluble minerals such as calcium and magnum carbonates
3- color is usally red-brown from iron oxides that form above and wash down

C- horizon
made of slightly weathered parent material (rock fragments)

unweathered rock
climate
-tropical soils form in areas with high temp and heavy rainfall. A thick infertial soil profile are results of heavy rain.
- grassland soils form in area with enough rainfall for heavy grass but not trees about 1 meter thick and fertial
- forest soils form in humid regions with cool seasons. soil profile is less then 1 meter thick with well devolped a,b and c horisions
- desert soils form in very dry climents. soil profile is a few centimeters thick and be very firtile when they are watered
-arctic soils form at high elevations and high altitudes poorly drained surfaces and the bottom layers are constantly frozen.

Mass movements

Movement of loose earth material down a slope

    • gravity is an aid in weathering and erosion. step 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 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 DOWN THE SLOPE OF A HILL OR MOUNTAIN.(AVALANCHE -SNOW, ICE, ROCK AND SOIL

TALUS- IS A PLILE OF ROCK FRAGMENTS AT THE BASE OF A CLIFF.

6) WIND EROSION



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.

WIND EROSION IS GREATEST IN ARID CLIMATES (LOW PRECIPITATION WITH LITTLE VEGETATION. (DESERTS 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 DEPOSITION OCCURS IN AREAS WHERE WIND VELOCITY DECREASES

dunes2_hirise_big.jpgsanddunes - ARE PILES OF WINDBLOWN SAND THAT HAVE A GENTLE SIDE AND A STEEO SIDE.
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)



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.

7) GLACIERS

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 compress and re crystallizing
the lower layers become ice and begin flowing downward or outward because of overlying pressure.

alpine glaciers- occure in mountain regions above the snow line flow downhill and carve out u-shaped valleys
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continental glaciers- a glacier that spreads over a wide geographic area form in polar area where the snow line is close to sea level and wide areas are above the snow line

20,000 years ago new york state was covered by a huge ice originated in canada

glacier movement- 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 downward

glaciers move more rapidly at the surface than at the base and faster at the center than at the slides friction with the valley walls slow the flow
  • flow at a rate of a few cm per day*

crevasses- are cracks across the width of the glacier that form when glaciers move over steep slopes
StubaiCrevasses.jpeg
ice fronts is the end of a glacier
the ice fronts is stationary as log 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 ten the rate at which it melts

Pieces of rock are picked up as glaciers move and then are dragged along the bedrock an or valley wall
fine sand acts as sandpaper and polished the bedrock
larger sediments leave long parallel scratches called striation
striations show the direction of movement

Calving- is when blocks of ice breaks off into the sea

glacier through are formed when a glacier carve out a valley forming a u-shaped valley
vall
  • cirque-Geology a half-open steep-sided hollow at the head of a valley or on amountainside, formed by glacial erosion

  • arete-a sharp mountain ridge.

  • horn-a sharp promontory or mountain peak.

  • col- a break in a arete
  • truncated spur-
  • tarn- a small lake at the base of a cirque
  • hanging valleys-a valley that is cut across by a deeper valley or a cliff.
  • crevasse-a deep open crack, esp. one in a glacier.
  • roches moutonees- an outcrop of bedrock which has become elongated.sculptured by a glacier one side is smooth and the other is left rough
  • striations-
  • drift-be carried slowly by a current of air or water
  • till-an unstratified sediment consisting of particles of various sizes anddeposited by melting glaciers or ice sheets.
  • moraine
  • A-lateral- forms along the side of a glaacier
  • B-medial- merging lateral moraines of two glaciers form from a moraine in the middle of the glacier
  • C-ground- a melting glacier deposites of till in a thin layer over a broad layer
  • D-recessional- deposites of till that form from at the end of a glacier as it retreats
  • E-terminal- the end moraine found at the farthest advance of a glacier
  • outwash plain- material carried away from a glacier by meltwater and depositedbeyond the moraine.
  • kame- a steep-sided mound of sand and gravel deposited by a melting ice sheet.
  • kettle-
  • drumlin- low oval mound or small hill, typically one of a group, consisting of compacted boulder clay molded by past glacial action.
  • rock flour-finely powdered rock formed by glacial or other erosion.
  • eratics-not even or regular in pattern or movement; unpredictable
  • esker-a long ridge of gravel and other sediment, typically having a winding

Erosion and Deposition

Running water

  • Erosion- is the process by which earth materials are moved by natural agents like water, wind , and ice
  • RUNNING WATER
  • - most effective agent of erosion is running water
  • 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 bouldres as cutting tools to grind away at the stream bed. During this process the tools themselves wear down
  • angelCave.jpgChemical the water dissolves soluble minerals
Rivers carry rock materials in three ways

  • Solution- this is material that is dissolved from the bed rock. most commonly found in solution are compounds of calcium and magnesium
  • Suspension- when small rock particials such as 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- is indicated by both the total amounts of sediments in a stream and by the size of the particalies being moved
  • THE STREAMS 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 generaly determined by the steepness or gradient of its bed
  • A stream moving at high speeds with a high discharge can carry much larger sediments the a slow moving stream. EX 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 get below the water table This wearing away of the land to form a stream valley is called headwater erosion
  • A divide is an area of high land that seperates one river from another
  • On eaither side of a divide a river system may form
  • WATERSHED- is all the land that drains into the river eaither directily or through its tributaries
WATER FALlwatershed_800.jpg
  • water flowing over a steep cliff will result in a water fall. water \falls are not perminent structures
  • Undermining is the erosional process ocurring at the base of a waterfall. here water carrying sediments plunges down and back into the stream bed and cliff below. This causes the rocks at the top of the falls to over hang. over time this overhang will collapse and the stream will move back towards its source
  • river 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 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
  • waterfall.jpgMEanders are broad curves river
  • Erosion is greatest on the outside of a meander where water is flowing the fastest
  • deposition is greatest on the inside of the meander where the water flows slower
river_dep.jpg
Deposition is greater on the inside of the meander where the water flows slower

Oxbow lake- meanders can only become only so large before they break throught into another meander. The river then deposites mud and silt anlong the end of the abandoned meander. The now seperated meander becomes a lake

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Running water deposits well sorted particals
Vertical sorting- when sediments are suddenly deposited into the water. the partical size with the largest on the bottom and smallest on the 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 shore and smaller particles being carried out into the body of water to be deposited
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River vocabulary Chapter 10


  1. river deposition- river deposits their bed load when they slow down this can occur in slope of land decreases the stream channel widens
  2. 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
  3. A stream is a flowing body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics
  4. source - the fouintain head of a stream where water begines to folw
  5. mouth- the opening of a stream where it empties into another water body

  6. tribuatry- any stream that flows water to another stream
  7. watershed-an area or region drained by a river
  8. channel- the area of a valley occupied by running water
  9. valley- any low writing land bounded by higher ground
  10. meanders- a winding curve or bend of a river
  11. flood plain- low lying ground adjacient to a river
  12. delta- a level fan shaped deposit formed at the mouth of a river
  13. alluvium-deposits made by streams on flood plains sediments are sorted by size
  14. alluvium fan- a fan shaped deposite found at the base of a steep mouintain
  15. cone- a steeper alluvium fan forms in deserts or semi arid
  16. oxbow lake-
  17. natural levee-
  18. yazoo stream-