weathering Flashcards
weathering definition
the breakdown of rock to form transportable material
5 factors controlling weathering
- rock properties
- climate
- presence of soil
- length of exposure time
- topography
moving from the north to the south pole, what are the 7 climates
polar temperate subtropical tropical subtropical temperate polar
3 types of weathering
chemical and mechanical and biological (combo)
dominant process of weathering in cold and arid climates
mechanical weathering
agents of mechanical weathering
- pressure release
- water (freeze-thaw, wetting-drying, crystallise salt)
- heat
how does mechanical weathering increase the weathering process as a whole?
increases total surface area exposed to further weathering - cascades
explain pressure release weathering
rocks form at high pressures underground . When they rise to the surface the pressure on them decreases and the rock mass expands. joints form.
true or false. All rock masses at or near the surface contain joints?
true (virtually all)
exfoliation (sheet joining)
rock breaks apart in layers parallel to surface, as it is uncovered and expands
frost wedging
expansion of ice in joints in cold and alpine environments
wetting and drying (common on the coast)
clays absorb water and expand, dry and shrink. continuously.
salt crystallization (aka haloclasty) what? where?
saline solutions seep into joints and the water evaporates, leaving salt crystals.. These expand when heated and pressure exerted on rock. common in arid climates and coasts
thermal expansion
extreme ranges in temperature shatter rocks in DESERT environments. Different expansion rates of rock minerals causes shattering
what is one thing essential in chemical weathering
water, therefore prevelant to wet regions
4 types of chemical weathering
- dissolution
- hydrolysis
- oxidation
- hydration
dissolution
complete removal of mineral from rock. eg acid rain
hydrolysis
water changes composition and size of minerals in a rock. Which are less resistant to weathering. rock is then physically broken down
in what rock is hydrolysis common
granite
red soils produced from
oxidation weathering
hydration
water added to crystal structure which creates a new mineral of greater volume.
according to Bowen’s reaction series, the first to crystallise will be the ______ to weather on the goldich series
first
roots splitting rocks apart and producing acids, are an example of?
biological weathering
chemical weathering most effective in polar regions, TRUE/FALSE?
FALSE. least effective here, needs warmth and moisture
4 effects of weathering
- strength decrease
- loss of elasticity
- density increase
- increased porosity
erosion
detachment and transportation of weathered surface particles
soil erosion snowball effect
removes topsoil which provided the nutrients and water for plant growth. less vegetation leads to more erosion and so on…
severe soil erosion forms…
gullies
where is soil erosion most active?
where it is difficult for rain to infiltrate into the ground
describe ‘piping’?
subsurface soil erosion. invisible and therefore very dangerous . eg sinkholes
in arid areas, what causes soil erosion?
wind. can also form deserts in semi-arid places
