Weathering Sprint Flashcards
omg where is all this dust comign from?!?
Physical weathering
When solid rock is fragmented by mechanical processes. No change in chemical composition.
Chemical weathering
When the minerals in a rock are chemically altered/dissolved.
Relation between physical/chemical weathering
Chemical
weathering weakens rocks and makes them more susceptible to physical weathering.
The smaller the pieces produced by physical weathering, the greater the surface area available for chemical weathering
Erosion
The process by which particles produced by weathering are dislodged and removed from
their source, usually by means of currents of water or air
4 Main Weathering Factors
- Properties of parent rock
- Climate (rainfall and temperature)
- Presence vs absence of soil
- Length of exposure
Chemical Weathering on Granite
As water penetrates the rock, feldspar, biotite, and magnetite within granite begin to decay/dissolve. Quartz remains, but the overall structure is weakened until it eventually fragments.
Chemical weathering’s effects on silicates
- Leaches away cations and silica.
- Hydrates minerals.
- Makes solutions less acidic.
Damp soil weathering
Soil keeps water constantly in contact with rock surface, causing it to continuously weather.
Soil is also more acidic than rain, so weathering with acid occurs more quickly.
Plants and bacteria in the soil add even more acid.
Chemical Stability
A measure of a substance’s tendency to retain its chemical identity instead of reacting with other substances. Determined by solubility and rate of dissolution.
Solubility
How much of a mineral can be dissolved into water before the water becomes saturated. Higher solubility means lower stability.
Rate of Dissolution
The amount of a mineral that dissolves into unsaturated water in a given amount of time. Higher rate of dissolution means lower stability.
Zones of Weakness
Natural regions of rocks where they are most susceptible to cracking. Can split along foliated parallel cleavage planes, sedimentary bedding planes, etc.
“Massive” rocks
Rocks with no natural zones of weakness. Tend to crack along regular, spaced-out fractures instead.
Activities of Organisms
Animals can burrow through/crack rocks, while plant roots can split cracks open further.
Frost Wedging
Breakage resulting from frozen water expanding within cracks.
Exfoliation
Layers of rock peel off from the surface over time. WE DO NOT KNOW WHY.
Humus
Organic matter in soil
Soil
Layers of material made from broken down rocks, with more fun stuff added in over time. Easily eroded.
Soil inputs
Weathered rock, organisms, and dust.
5 soil factors
- Parent material
- Climate
- Topography
- Organisms
- Time
Soil transformations
When materials added to/removed from a soil alter its properties
Soil translocations
Lateral and vertical movements of materials within soil. Mainly done by water, but also by organisms.
Soil profile
Composition and appearance of a soil. Consists of up to six horizons.
Soil horizon
A distinct layer of varying color/texture, visible in vertical sections of exposed soils
O-horizon
Thin horizon at the top. Loose leaves and organic detritus.
A-horizon
1-2 m thick at most. Second layer. Darkest layer–contains highest concentration of humus.
E-horizon
Third layer. Clay and insoluble materials.
B-horizon
Fourth layer. Sparse organic matter, soluble minerals, iron oxides. Exact minerals affected by climate.
C-horizon
Fifth layer. Slightly altered bedrock, clay from chemical weathering.
R-horizon
Sixth layer. Unaltered bedrock.
Paleosols
Ancient, preserved soils that can provide info about ancient climates.
Stream power
Product of a stream’s slope and its discharge. Affects how a stream erodes soil/rock.
Streambed’s erosion resistance
Product of the volume and the particle size of the sediment in the stream channel. Affects how a stream erodes soil/rock.
Relation between bedrock erosion and stream power
DRAMATIC increase with stream power!
Three processes that erode bedrock
- Abrasion by suspended sediment particles
- Drag force from the current
- Glacial erosion
