Weathering + Mass Wasting Flashcards
Denudation
removal, wearing away, disintegration of rock material
3 types of denudation in order
1) weathering = breaking down of rock into smaller pieces by atmosphere
2) mass wasting = short distance VERTICAL movement of broken rock material
3) erosion = (horizontal) removal, transportation, deposition of rock material over wider areas
What are rock openings
1) Microscopic openings
2) joints
3) faults
4) lava vesicles
5) solution cavities
Microscopic openings
1) consist of spaces between crystals of igneous or metamorphic rocks
Joints
VERTICAL Cracks that develop as a result of stress BUT rocks do not show noticeable displacement along breaks
most important of all rock openings in facilitating weathering
Bedding Plane
horizontal crack (similar to joint BUT not vertical)
Faults
Breaks in bedrock caused by forced displacement of rock structure
Lava vesciles
holes of various sizes that develop in cooling lava when gases aren’t able to escape
solution cavities
holes formed in carbonate rocks (limestone) by soluble minerals dissolving + being carried away
Joints vs faults
Joints = no displacement
Faults = displacement
Types of weathering agents
1) mechanical
2) chemical
3) biological
Mechanical Weathering
1) Physical disintegration of rock without changing composition
(grinding)
2) occurs at surface 3) Examples:
- frost wedging (cold places) or salt wedging (hot places w. capillary reaction)
- temp changes (think wildfires) cause rocks to expand + weaken –> mini fractures form
- exfoliation = curved layers peel off bedrock, creating shapes like Halfdome (need bedrock)
- biotic processes = plant roots can spread rocks apart
Chemical Weathering
1) decomposition of rock by chemical alteration of minerals
2) requires moisture + surface area –> finely grained materials decompose more rapidly
Examples of chemical weathering
1) oxidation = when oxygen (in water) comes into contact with rock –> produces iron oxide
2) Hydration = water added to compound + becomes part of it –> forms hydrates (increases volume, contribute to disintegration)
3) hydrolysis = water added to compound + breaks it up i.e. silicate materials
4) carbonation = carbon dioxide dissolved in water, producing carbonic acid –> reacts with carbonate rocks to produce calcium bicarb –> forms stalagmites/tites
5) spheroidal weathering = thin rock layers peel off boulders, rounding it. outcome of hydration
Biological Weathering
1) weathering that involves living organisms
2) examples = plant roots into cracks + crevices
3) lichen remove minerals from rock + alternate btwn wet/dry, weakening rock –> leading to weathering
4) burrowing by animals
Weathering in diff climates
1) High temps + abundant precipitation = lead to more weathering
2) moisture more important than temp
3) desert regions = more mechanical than chem. weathering bc lack of water
$4) shallow weathering in tundra/desert + deep weathering in trop. rainforest
What factors influence mass wasting
1) angle of repose
2) water
3) clay
4) permafrost
Mass wasting factor = angle of repose
1) angle of repose = steepest angle where rocks/soil don’t slide off
2) balance between gravity + cohesion of rock to surface
Mass wasting factor = water
1) addition of water = lubricating medium + diminishes friction btwn particles
2) reduces angle of repose
Mass wasting factor = clay
1) clay becomes very slippery when absorbs water
2) quick clays = change from solid mass to near liquid very quickly
Mass wasting factor = permafrost
contributes to mass wasting in subarctic regions + high latitudes
Types of mass wasting
1) fall
2) slide
3) flow
4) creep
Mass wasting = fall
1) falling of rock downslope
2) Rock that falls called talus
3) dry + fast
Slide
1) abrupt + rapid
2) top of hill has a deep scar –> exposed bedrock + debris
3) more moist than fall –> if extremely moist it’s mudflow
Flow
1) becomes unstable because absorption of water + moves downhill
2) can vary in speed, depending on friction
3) gravity is impelling force + water is catalyst
4) Earthflow = portion of water-saturated slope moves downhill
5) mudflow = rapid movement of wet material through canyon/valley + deposited in fan-shape
Creep
1) slowest + dry
2) very gradual downhill movement of regolith that hard to notice
3) occurs mostly on steep lightly vegetated slope
4) caused by freeze/thaw cycles –> freezes moved upward bc of increasing vol of ice BUT when it thaws particle settles slightly downslope
Solifluction
1) Special form of creep
2) restricted to high latitude + high elevation tundra
3) thaws BUT water not able to penetrate permafrost, so active layer (Above frost) becomes oversaturated + moves downhill
Differential weathering
1) All rock does not weather at same rate or to same extent
2) some rocks easily weathered –> weak
3) other rocks –> stronger + more resistant to weathering
What are agents of erosion
1) wind
2) water (biggest factor)
3) ice
A Climate weathering type
1) Chemical - hot + lots of water draining through –> lots of oxygen WHICH is why there is lots of oxidation –> laterization = red soil (bc of iron)
2) No mechanical = too hot for frost wedging + not enough bedrock for exfoliation
E Climate weathering type
1) No chemical = standing water –> soil is saturated + no oxygen –> no chemical reactions
2) mechanical = frost wedging + temperature fluctuations
B, C, D Climate weathering type
1) BOTH MECHANICAL + CHEMICAL
B climates = mainly mechanical since not enuf water for chemical weathering
Describe how mass wasting varies by moisture + speed
1) As you add moisture: rockfall –> landslide –> mudslide
2) Speed: Solifluction (slowest) –> earthflow –> mudflow
3) Slowest + driest = creep (poles tilting bc ground moves v slowly)
FLOWS NEED WATER
