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What is Weathering?What is Weathering?The breaking down and changing of rocks near Earth’s surface
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Mechanical (Physical)Mechanical (Physical)Weathering?Weathering?
Physical forces break rock into smaller pieces without changing the rock’s composition.
Mechanical Weathering-Mechanical Weathering-In nature there are 3 main causes to mechanical weathering:Frost wedging, unloading, and biological activity
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Frost WedgingFrost WedgingExpansion of freezing
water in cracks and crevices
Eventually breaking rocks into pieces
• Sections of rock that are wedged loose may tumble into large piles called talus
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UnloadingUnloading• Large masses of
igneous rock may be exposed through uplift and erosion of overlying rocks
• Resulting in reduced pressure
Exfoliation—slabs of outer rock separate and break loose
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Biological ActivityBiological Activity• The activity of plants- roots
breaking rock
• burrowing animals-moving rocks to places where weathering more rapidly occurs, and humans
• Decaying organisms- producing acids
• Humans- because of deforestation, creation of roads, and blasting mineral
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Chemical Chemical Weathering?Weathering?
the transformation of rock into one or more new compounds
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Oxygen, water , and carbon dioxide are in chemical weather
Water: most important agent of weathering. It picks up CO2 and SO2 in the air which forms acid rain.
Or dissolves these compounds into cracks of rocks
Agents and Evidence of Chemical Agents and Evidence of Chemical WeatheringWeathering
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Rate of WeatheringRate of WeatheringHow fast the rocks
erodeTwo factors• Rock characteristics
• Mineral composition and solubility
• Climate• Temperature and
moisture• Favors high
temperature and abundant moisture
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SoilSoilpart of theregolith that supportsthe growth of plants.
Regolith: layer of rock and mineral fragments that covers Earth’s land surface.
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Characteristics of Characteristics of SoilSoil
Soil CompositionSoil has four major
components◦ A. Mineral matter
(broken-down rock) ◦ B. Humus (decayed
remains of organisms) ◦ C. Water◦ D. Air
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Characteristics of Characteristics of Soil Soil
Texture refers to the proportions of different particle sizes.
A. Sand (large size)
B. Silt – feels like flour
C. Clay (small size)
D. Loam (a mixture of all three sizes) is best suited for plant life.
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Time, Climate, Time, Climate, Organisms and SlopeOrganisms and Slope
Time: The longer a soil has been forming, the thicker
it becomes.Climate Greatest effect on soil formationOrganisms Furnish organic matter to soilSlope Steep slopes often have poorly developed soils.
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Soil Types Location Contents
Pedalfer under forest vegetation
iron oxides and aluminum-rich clays in the B
horizon
Pedocal drier grasslands Calcium carbonate
Laterite Hot, wet, tropical climates
Intense chemical weathering to the top layers of soil
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How does How does water erode the water erode the
soil?soil?Rain uses gravity as
a force to move soil.Flash flooding and
runoff of water causes erosion
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Processes of Water Processes of Water ErosionErosion
1. Sheet erosion - 2. Rills (tiny streams)3. Gullies (trenches)4. Transports sediments for
deposits.
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What is Mass What is Mass Movement?Movement?
The transfer of rock and soil down-slope due to gravity
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Triggers of Mass MovementTriggers of Mass MovementWater Heavy rains and rapid melting
of snow
Oversteepened Slopes The steeper the slope the greater the chance for movement
Removal of vegetation
Roots keep the soil intact. Removing plants causes erosion
Earthquakes Aftershocks dislodges rocks
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Classification of Classification of Mass MovementsMass MovementsRockfalls occurs
when rocks or rocks fragments fall freely through the air.
Avalanchesextremely rapid
movement of earth material or snow
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SlidesA block of material moves
suddenly along a flat, inclined surface.Slides that include segments of bedrock are called rockslides.
Slumps The downward
movement of a block of material along a curved surface.
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Flows contain a large
amount of water. Mudflows move
quickly and carry a mixture of soil, rock, and water
Earthflows move relatively slowly and carryclay-rich sediment.