Weathering. the process that produces change in the surface of rocks exposed to the atmosphere...
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Transcript of Weathering. the process that produces change in the surface of rocks exposed to the atmosphere...
WeatheringWeathering
Weathering the process that produces change
in the surface of rocks exposed to the atmosphere and/or hydrosphere.
Two Types OF Weathering:Two Types OF Weathering: Physical
weathering is breaking rock by force.
ex: hitting, scratching, cracking
Chemical weathering is where the rock material is changed into another substance by reacting with a chemical.
Frost action (ice wedging)-
Water seeps into small cracks in rocks. When the water freezes it expands creating great pressure. The crack widens and allows water to seep deeper into the rock.
Biological ActivityBiological Activity Plant action-
Tiny root hairs seek out small cracks and pits in rock. Once the root hairs find a place they grow and expand. The expansion causes great pressure and cracks the rock.
UnloadedUnloaded Exfoliation
Rocks formed deep in the Earth are made under high pressure. When the pressure is released the rocks expand & crack. May also be caused by alternate heating and cooling of rocks by weather conditions.
Chemical WeatheringChemical Weathering Oxidation-
Oxygen in the atmosphere chemically reacts with minerals. ex.: rusting of a nail
Water **** MOST IMPORTANT !!!!!Minerals are dissolved in water. ex.: Halite, calcite
Acid- Carbonic acid:C02 dissolves in rain water forming a weak acid
Acid Rain: Sulfur Dioxide in the atmosphere dissolves in rain water forming a strong acid (sulfuric acid).
Chemical WeatheringChemical Weathering
Chemical WeatheringChemical Weathering
Ex. Of Chemical WeatheringEx. Of Chemical Weathering
Rates of weathering will be influenced by:Rates of weathering will be influenced by:
Surface area exposed - weathering occurs on the surface.
More surface exposed, the faster the weathering will occur.
A full, solid block has the least surface area.
The interior is safe from exposure.
A smashed piece has greatest surface area exposed. The interior can now be attacked.
Mineral composition- some minerals are more resistant than others.
– ex.:Quartz is resistant to chemical and
physical weathering.
Rates of Weathering will depend on:Rates of Weathering will depend on:
Climatic Conditions:Cold and/or dry climates favor physical weathering. Warm and wet climates favor chemical weathering. Frost action works best in areas where the temperature fluctuates wildly.
Rates of Weathering will depend on:Rates of Weathering will depend on:
Soil - The product of weatheringSoil - The product of weathering
Soil- rocks, minerals (mainly sand and clay), and organic material (regolith and organic matter)
Soil forms layers of different characteristics called horizons.
oA
E
B
C
R
TOP SOIL
SUBSOIL
What are the main components of soil?What are the main components of soil?
Mineral Matter Air Water Organic Matter
Soil Components (volume basis)
What are the FACTORSthat make SOIL?What are the FACTORSthat make SOIL? TIME
1000’S TO 10,000’S OF YEARS
LAY OF THE LAND / “SLOPE”TOPOGRAPHY
LIVING ORGANISMSANIMALS AND PLANTS
CLIMATEHOT/COLD, WIND/RAIN
PARENT MATERIALROCKS AND MINERALS
Physical land features
Why is soil important ?Why is soil important ?
Necessary for the growth of rooted plants which support our life system !!!!
ErosionErosion
Movement of sediments (soil) from one location and deposition of it another place.
Can occur in 2 ways
2 ways erosion can occur ….2 ways erosion can occur ….
Earth processes which move material on the Earth’s surface over long periods of time, such as weathering and gravity
Human activity which moves material on the Earth's surface over short periods
Transport Agents of ErosionTransport Agents of Erosion
WaterRainStreams and riversOceanIce (glaciers)
Wind Gravity
Erosion by WaterErosion by Water
Erosion by WindErosion by Wind
Erosion due to gravityErosion due to gravity
Example of Human Made ErosionExample of Human Made Erosion
Erosion at Construction SiteErosion at Construction Site
Silt fencing during construction doesn’t necessarily stop all erosion
Silt fencing during construction doesn’t necessarily stop all erosion
How Erosion Effects the Environment
How Erosion Effects the Environment
#1 Pollutant to our Waters#1 Pollutant to our Waters
Sedimentation in Rivers Sedimentation in Rivers pollutes water with soil particles damages water ecosystems through reduced
sunlight for aquatic plants and animals increases water treatment costs for human
water consumption reduces the depth of rivers, thus creating
waterways that can't be navigated by commercial crafts
Removal of topsoil from land areasRemoval of topsoil from land areas
prevents plant growth alters ecosystems, thus reducing the
biodiversity of life destroys crops reduces agricultural food production reduces farming income
Wind ErosionWind Erosion
increases the amount of particles in the air reduces visibility reduces air quality causes breathing problems (asthma, etc.)
What can help prevent erosion?What can help prevent erosion?
Plants can help prevent erosion! Look at the roots on these grasses. Roots help hold the soil in place so that it doesn’t
wash away.
Plants can help prevent erosion! Look at the roots on these grasses. Roots help hold the soil in place so that it doesn’t
wash away.
Plant roots
Mass MovementMass Movement
The transfer of rock and soil downslope due to gravity
Triggers of Mass MovementTriggers of Mass Movement
Saturation of material with water Oversteepened slopes Removal of vegetation Earthquakes
Types of Mass MovementsTypes of Mass Movements
Based on:Kind of material that movesHow it movesSpeed of movement
RockfallsRockfalls
Usually happens on oversteepened slopes due to mechanical weathering (freeze-thaw)
SlidesSlides
Occur suddenly and can reach speeds of over 200 km/hr
Usually occur in the mountains
SlumpsSlumps
Do not occur suddenly Usually happens in clay soil
FlowsFlows Contains a large amount
of water Mudflows – move quickly Earthflows - slower
CreepsCreeps
Occur gradually over time Usually due to freezing and thawing of soil
The EndThe End
Chapter 5