1 Flashcards
what are the two forms of weathering?
mechanical and chemical
what is weathering and how is it different from erosion ?
breaking materials down (decomposition of solid earth materials
erosion = movement of materials
why is water critical to weathering?
abundent on earths surface
-exists in 3 phases
1.it expands when it freezes
2. it has a high surface tension = capillary action(pulls itself along thin sheets of rock
sneaks in then expands and blows cracks oppen
3. water is a universal solvent
it has both positive and negative charge meaning it can disolve cations (+) and anions (-)
What are the processes of mechanical weathering?
Frost cracking
unloading/fracture
vegitation/roots
what is frost cracking?
thin film of water seeps into cracks and expands and cracks rock, happens repeatedly lengthening the crack
what is unloading?fracturing (exfoliation or sheeting)
rock is under pressure from all around it, then is exposed and only pressure on one side and other side expands like sponge and cracks at surface
what is vegitiation roots weathering?
roots crack stuff
what is chemical weathering?
breakdown of minerals and rocks through chemical reactions with (water,co2, oxygen, and organic acids)
what are the processess of chemical weathering?
hydration/hydrosis
oxidation
carbonation/solution
what kind of rocks do you need for landscape scale chemical weathering?
limestone and marble
what is karst?
forms caves and then collapses into valleys then sink holes, then karst valleys
-two things important for karst: precipitation and soluble rocks
what is mass wasting?
movement of earth material under force of gravity down
F=Gm1m2/d2
what is an angle of repose?
highest and most stable slope
what is a creep?
when something creeps along from frost
what is soilflection?
permafrost must exist
top layer of permafrost melts but lower layers do not, top part slides down hill, can happen with clays as well
what is a slump?
slower than a flow, slide or fall
curved plane of falure
intact rotated blocks
what is a flow?
turbulent motion of earth material down a slope
eroded bed plane
speed=water content
consists of mud, debris, water and earth
what is a slide?
flat plane rock structure
what is a fall?
crate a talis slope loose material forms ramp at bottom like at tiber dirt cliffs
Rock avalanche- Surtzstrom
you know what an avalanche is now make it a rock one, forces rocks to go a lot longer than usually posible, very high energy
what is a stream?
any channelized flow, even a river is a stream
what is watershed?
area above any reach that contributes water
what is a reach?
any defined segment of stream
what is a profile slope- Gradient?
slope form along a channel V=velocity S=sediment load E=erosion D=deposition
what is capacity as relates to a stream?
amount of sediment=amount of water
what is competence?
size of the particle
What is a thalweg?
area of a channel with highest velocity
what is base level?
lowest elevation of flow
ocean is the ultimate base level
what is the ultimate driving force of a stream?
gravity
What is a dynamic system that always strives for equilibrium with enviornment?
a stream because no mater how much discharge is the channel size will match it in response
what are the external inputs of a stream?
discharge sed load regional slope base level bedrock structure
What responses can a stream have to changing inputs?
change in channel size and channel form or shape
What types of channels are there?
straight, braided, meandering,
what is a straight channel?
valley confined, headwaters tend to be steeper, erosion is dominate and it erodes down into valley
what is a braided channel?
wide channel with branching smaller channels within, wide active channel, sand bars move
- common in high sediment load
- variable discharge
- slightly steeper than meandering, and not as steep as straight
what is a meandering channel?
sinuous and snaky -has loose banks -low slope=low velocity it has both -fine grain sediments erosion on one side =deposition on other side making a snaky lateral pattern
What is a valley?
v shaped, in headwaters it is steeper
what is a floodplain?
area in which a river floods
- rich farmland
- floods bring new good soil sediments
- levies are deposited on edge of normal channel
What are terraces
levels of a stream base level on each side, do not always match up on both sides
what is a delta?
end of a stream into a body of water
ends with distributaries that move around to distribute sediments in a fan life formation, happens because of a sudden change in elevation
What is a floodplain?
area around a channel used to accommodate rise in quantity of water
it decreases the velocity of the water and the discharge of the water as well as the quantity of water downstream
100 year flood:
measurement of risk of flood according to time of floods, based on flood history, based on percentage of likelihood of flood any given year
has many problems, like sometimes 100 years has not been recorded and human change of rivers
in what region of the earth are deserts centered and the sun centered
in between the tropic of cancer and the tropic of capricorn (aka the equater is in between these two lines of longitude
Weathering of arid lands:
Fluvial processes:
MEchanical
erosion
What are slot canyons?
formed in two ways
1. from high flow, flashy floods, episodic
2. braided : high sediment load, variable discharge
wash arroyo wad
fans young to old?
- fans
- bajada
- peidmont
- inselberg (no more erosion posible)
what does it mean to be pluvial?
evaporation lakes,
water goes in but no outlet except evaporation
what is the Eolian processes and pattern in arid lands?
erosion- minimal, sandblasting (about 50 cm from ground)limited
transportation- sand saltation(bouncing along) or silt and clay suspension in air
Deposition- sand into dunes(beach river or lake) and silt and loess into deserts or rivers
What three things does wind need to be a factor in erosion?
- low vegitaion
- loose sediments that are small
- and lots of wind
what is deflation in geology?
removal of fine sediments resulting in nothing but a concentration of larger rocks on surface
What is venifacts?
sand blasted polished rocks
Draw a picture of a dune and label?
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What is loess
blanket of wind deposited silt
draw example of frost cracking?
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draw example of unloading?
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Draw example of karst time line?
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Draw example of mass wasting?
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Draw example of slump, flow, slide, and a fall
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Show examples of drainage patters?
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Show example of profile slope of a channel
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Show example of a cross section accross a channel
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Show example of a thalweg map view and cross section view
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show example of how base level change effects the gradient or baselevel of a stream
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Show example of each of the three stream types:straight, braided and meandering
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show pic of a valley and floodplain and a terraces
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show example of earth with weather regions
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show image of slot canyons from above
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show images of fans old to young
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