Weathering & Erosion By Brooke And Lillie
Published on Nov 25, 2015
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PRESENTATION OUTLINE
WEATHERING
- The process of wearing away and changing.
- Rocks are broken down in smaller pieces by the effects of weather.
- Earth's surface constantly changes due to weathering process.
- This process can take millions of years to happen or happen relatively quickly.
MECHANICAL WEATHERING
- Weathering from external services: freezing and thawing.
- Takes place when rocks are broken down without any changes in the chemical nature of rocks.
- Rocks torn apart by physical force.
CHEMICAL WEATHERING
- Weathering when a chemical (like acid rain) breaks down rocks.
- Break down bonds holding rocks together causing them to fall apart forming smaller pieces.
- Common in locations with lots of water.
DEPOSITION
- Laying down of sediment carried by wind ,water , or ice.
- Happens every time erosion happens.
- The opposite effect of erosions.
- Deposition in water always causes a sorting of particles (size, density, or shape) - for example the biggest on the bottom and smallest on top.
EROSION
- Process by which soil and rock particles are worn away and moved elsewhere.
- Removal and transport of sediment.
- Agents of erosion: Gravity, running water,moving ice , wind, wave action.
- Transport is the cycle processes of moving sediment.
DEFLATION
- Removal of loose , fine grained particles by wind.
- Lowers the land surface by removal of the small particles leaving the coarser grained behind.
Photo by Konabish ~ Greg Bishop
SANDSTORM OR DUSTSTORM
- Strong winds blow loose sand and dirt from a dry surface
- Caused by low vegetation and disturbance of soil
- Can blind drivers, knock out electricity and ground air flights
- Sandstorm typically used in context of a desert storms. Dust storm is typically used when fine particles are blown long distances.
WINDBREAK
- Attempt to control erosion.
- For example a field windbreak is a planting of trees and shrubs in a line to reduce wind speed in open spaces.
- Scientists study wind tunnels to help design windbreak.
- Sometimes called 'wind fences '.
ABRASION
- Wearing down of surfaces by grinding action of particles in the wind.
- Surface shaped by wind blown objects ( like sandblasting).
LOESS
- Wind deposits of finer sediments.
- Win blown , silt , and clay deposited layer on layer over a large area.
- Make very fertile soils in many regions of the world.
DUNES
- For a sand dune to form there must be a lot of sand and steady winds.
- Located in deserts or seashores.
- Beach dunes are usually made of Quartz.
SOIL EROSION
- Natural processes where soil is removed.
- Agents of soil erosion are water and wind.
- Big problem in US in 1930s dust bowl- winds removed the soil.
- Half the topsoil on the planet has been lost in the last 150 years.
- Leads to increased pollution and sediments in streams and rivers.
OVERGRAZING
- Happens when vegetation in an area is exposed to intensive grazing for an extended period of time; for example livestock (too many animals in an area or not properly controlled grazing).
- Plants become weaker and have shorter roots which means they might die during the winter .
- Overgrazing increases soil erosion.
FOREST HARVESTING
- Soil erosion in undisturbed forests is very low because of all the ground cover (" forest litter").
- Can be called " clear cutting" and most or all the trees in an area are cut down.
- It destroys natural habitats and contributes to climate change and increases soil erosion.
AGRICULTURAL CULTIVATION
- Cultivation of animals and plants for food, fuel, medicine and other products for humans .
- Man began growing crops 10,000 years ago.
- Organic farming is gaining in popularity since beginning in the 1940s.
MASS MOVEMENT
- Movement of massive bodies of soil, bed rock, rocks
- Earth materials moving down slope under the influence of gravity
- Caused by: Volcanic activity, Earthquake shocks Human modification, Vibrations from machinery, and Mudslides
SLUMP
- Moves materials as a large block along a curved surface; movement is slowly down a hillside
- A slipping of a rock happens when too much weight is added to an unstable slope or the slope is undercut
CREEP
- Slowest type of mass movement- entire side of a hill or mountain moves down
- So slow special equipment is needed just to measure the movement (less than one inch p
- Mass movement or mass wasting is movements of masses of bodies of soil, bed rock, rock debris, soil, or mud which usually occur along steep-sided hills and mountains because of the pull of gravity. This slipping of large amounts of rock and soil is seen in landslides, mud slides, and avalanches.
Mudflow
- Flow of water that contains large amounts of suspended particles and silt.
- Hillsides with soils rich in clay and not much vegetation experience mudflows in times of high precipitation
- Higher density and Viscosity than a stream flow
Rockfall
- Rocks cascade down a slope but not a large volume
- Usually occur at a very steep slope like a cliff face
- Rocks can be loosened by earthquake, rain, expanding ice, and plant roots
ROCKSLIDE
- Sudden rapid slide of bedrock
- Common canyons (example in the Salmon River Canyon where more than 5,000 feet exists between the top and bottom)
GLACIER
- Fallen snow that over many years compresses in a large thick mass of ice.
- Have the ability to move because of their mass flow like a very slow river.
- Some are hundreds of kilometers long.
Photo by christine zenino
PLUCKING
- Occurs when rocks become frozen to the base or sides of a glacier.
- As the glacier moves these rocks are removed from the ground and leave behind a hole.
MORAINE
- Rock debris carried or deposited by a glacier.
- Ground moraine is a blanket of debris under a glacier.
- Terminal moraine is a ridge like pile of debris pushed forward.
- Other types are lateral, medial, and recessional.
TILL
- Unsorted sediment deposited by a glacier.
- Sometimes called " Boulder clay".
- Ranges from clay sized to Boulder sized and can weigh thousands of tons.
ESKER
- Long narrow ridge of sand and gravel deposited by a meltwater stream marking the former location of a glacial tunnel.
- Channel deposited marketing the routes of rivers and streams that flowed on , in and beneath The glaciers.
- Comes from an Irish Gaelic word "eiscer " meaning "ridge".
OUTWASH
- Plain formed by deposit of sand and gravel carried by running water from the melting glaciers.
- Also called 'sandur' .
- May contain 'kettle lakes' where blocks of ice have melted leaving a depression.
CONTOUR FARMING
- Growing crops across or perpendicular to a slope rather than up and down the slope.
- The rows across the slope are designed to be as level as possible.
NO-TILL FARMING
- Growing crops without disturbing the soil with digging, stirring and overturning.
- Increases the amount of water that gets into the soil and increased organic matter retention and nutrients.
TERRACING
- Make or form sloping land into a level flat areas resembling a series of steps.
- Found on mountains.
METHODS USED AT CONSTRUCTION SITES
- Must submit " Soil and Erosion and Sediment Control plans" to local conservation districts.
- Stabilized construction access ( crushed stone ).
- Review permanent vegetative measures.
- Wire mesh in front of storm water inlets and storm water basins.
- Put in temporary measures while constructing to limit disturbance ( straw, mulch, silt fencing, crushed stone).
