Geomorphology Exam 1
Terms
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- In situ decomposition of rocks and minerals
- Weathering
- transport of weathered material
- Erosion
- most important factor that determines type of weathering
- climate
- disintegration of rock without chemical changes
- physical/mechanical weathering
- chemical/mineralogical composition of rock altered
- chemical weathering
- disintergration of rock due to changes in volume associated with pressure changes as the rock moves to the surface
- unloading
- large mound of granite shaped like an onion associated with unloading
- exfoliation dome
- water seeps into rock and freezes, form of physical weathering, forms talus
- freeze/thaw
- water pushed through rock by freezing water near the surface, produces felsenmeers
- hydrofracturing
- produced by hydrofracturing, large fields of broken up boilders and cobbles
- felsenmeers
- salt water percolates into rock cracks, when water evaporates, salt crystals form breaking the material
- crystal growth
- repeated heating and cooling of rocks causing rock to break apart
- thermal expansion/contraction
- repeated wetting and drying of shales causes rocks to break apart
- wetting and drying
- mud cracks
- dessication cracks
- mud sticks to rock edge, after drying, it shrinks and pulls grain off
- colloidal plucking
- trees, people, etc introduce weathering
- organic
- rocks falling on other rocks
- gravitational impact
- two important things in chemical weathering
-
1. Surface area
2. Water - Why is water important in chemical weathering?
-
Exposes fresh surfaces.
Medium for elemental exchange.
Takes part in a chemical reaction. - Types of chemical weathering:
-
Dissolution
Oxidation/Reduction
Ion Exchange
Hydrolysis
Carbonization
Hydration - disruption of mineral in water into ions
- dissolution
- mineral loses electron to oxygen
- oxidation
- mineral gains an e-, occurs mostly below water table
- reduction
- substitute one element for another element in a mineral without changing mineral structure
- ion exchange
- way of expressing mobility
-
Ion exchange
IP=charge/radius - chemical addition of H+ and OH- ions into a structure to create a new mineral
- hydrolysis
- carbonization
- minerals containing K, Na, Ca, Mg interact with cation from carbonic acids to form some sort of CaCO3
- addition of water into mineral structure to form a new mineral
- hydration
- most important control on weathering
- climate
- 9 Controls on Weathering
-
1. Availability of water.
2. Circulation of water.
3. Vegetation
4. Parent material
5. Temperature
6. Pressure
7. Topography
8. Time
9. Aspect - Weathehring rates are dependent on:
-
1. Parent material
2. Vegetation
3. Climate
4. Topography
5. Time - Product of granular disentigration
- Grus
- weathering of angular edges into rounded edges
- Spheroidal weathering
- bold, isolated outcrop that rises drastically from the ground and can be meters high
- tors
- weathering that looks like honeycomb on the side of the cliff, the cause is hydrolysis
- cavernous weathering
- weathered residue that becomes differentiated at depth into horizons
- soil
- layers of soil
-
O-> organic
A-> zone of leaching
B-> zone of accumulation
C-> no weathering - larger scale than tors, these are remnant rocks in hot/dry zones
- inselburgs
- broken up pieces of rock
- regolith
- ancient soil no longer going through soil forming processes
- paleosol
- landforms are interplay of what three things?
-
1. Driving forces
2. Resistive framework
3. Time - once stress is released, rock returns back to original shape/position
- elastic deformation
- rock remains deformed after stress is released
- plastic deformation
- behaves like a fluid
- plastic
- point at which a material no longer behaves elastically
- elastic limit
- amount of force required to cause failure
- strength
- amount of force required to break in direction of force
- shear strength
- amount of force required to break on a perpendiculat plane
- tensile strength
- amount of force require to crush a rock
- compressive strength
- mechanical resistance to relative motion of adjacent masses
- friction
- slow and steady continuous plastic deformation
- crepe
- Two types of friction:
-
1. Sliding friction
-well defined plane
-static
-dynamic
2. Interna friction - Effects of moisture:
-
cohesion
surface tension
fluid pressure - 2 Ways to measure shear:
-
1. Direct shear test
2. Triaxle Test (accounts for confining pressure) - ratio of driving forces to resistive forces
- Safety factor
- Two main types of mass movements
-
1. Flow
2. Slip - Difference between flow and slip
-
Slip- well defined surface
Flow- no well defined surface - Naming mass movement depends on:
- mechanism and material
- slow, down-slope movement of saturated soil
- solifluction
- rapid downward sliding along a plane
- landslide
- rock breaks loose and falls through the air
- rockfall
- forward rotation of a block while it falls
- toppling
- curved surface from which mass movement moves away from
- slump
- unsorted incoherent mixture of Earth with water or ice that moves downslope rapidly
- debris avalanche
- narrow valley in side of mountain where debris avalanches are common
- couloirs
- rock fused together during debris avalanche
- frictionite
- slow downslope viscous flow of saturated, fine grained material
- earthflow
- not as fine grained as earth flow
- debris flow
- heterogenous mixture of rock and debris
- mud flow
- high speed debris avalanche that moves downslope
- sturzstroms
- black substance on geologic surface
- desert varnish
- Surface to clouds
- evaporation
- clouds to surface
- precipitation
- surface to subsurface
- infiltration
- surface to ocean
- runoff
- discharge
- volume/time
- intensity
- amount of precipitation/unit time
- how often an event of a certain magnitude reoccurs
- Recurrence interval, #years in record/rank
- lines connecting maximum maximum precipitation in a 24 hour period
- isopluvial map
- annual average precipitation
- isohyet map
- amount of precipitation preceding a rainfall event
- antecedent precipitation
- amount of precipitation that falls and never reaches the ground
- interception
- Types of interception
-
1. Transpiration
2. Throughfall
3. Stemflow - Infilltration depends on...
-
porosity
permeability - empty space within soil and rocks
- porosity
- ability of rocks and soil to transmit fluids
- permeability
- movement of water as a broad sheet
- Horton overland flow
- smallest (cm-in) unit which precipitation can form
- rill
- many rills gathered together
- gulley
- flow longer than just a couple of days, but not year round
- euphermal
- elevation between top and base of a stream
- stage height
- is when stream tops stream banks
- flood stage
- max flood stage during an event
- crest
- plot of discharge vs. time
- hydrograph
- Shallow water=
- higher velocity
- 5 Ways a river carries material
-
1. Dissolution
2. Flotation
3. Ice
4. Suspension
5. Bedload - way of transport in which water dissolves minerals and transport them
- dissolution
- debris floats on the water due to surface tension
- flotation
- form of transportation which carries impurities
- ice
- velocity can keep objects from settling
- suspension
- anything that is being carried that is in contact with the bed of the river
- bedload
- type of bedload that bounces along bed
- saltation
- type of bedload in which transport material is always in contact with the bed
- traction
- Difference between valley and channel...
- Channel is where the water is flowing at any given time and the valley is much larger
- area between the channel and valley
- floodplain
- stream is straight with little, if any, variation
- straight stream
- stream has channels that bifrucate and merge back together, but are permanent
- anastomosing
- stream has channels that bifrucate and come back together, but they are not permanent
- braided
- stream with a sinuous path
- meandering
- whole scale movement of a meandering stream most commonly along deltas or oceans
- avulsion
- stream length/valley length
- sinuosity
- any stream that flows within the vally of a parallel stream
- yazoo stream
- elevated areas directly ouside the channel, but stil in the valley
- levee
- stream that has reached equilibrium between discharge load and slope
- graded stream
- more sediment than water, so net deposition
- aggradation
- more water than sediment, so net erosion
- degradation
- Type of degradation that cuts into bed
- incision
- rapid increase in velocity of water can cause bubbles, when bubbles pop they can create shockwaves that break rocks
- cavitation
- Order of Streams
-
1st- smallest
2nd- 2 1st
3rd- 2 2nd
4th- 2 3rd - Drainage density
- length (sum)/area
- river flows with the slope of the land
- consequent stream
- river has no preferred direction
- insequent stream
- selective headward erosion following courses along weakness
- subsequent streams
- originally consequent stream, but has been modified to flow in opposite direction
- obsequent stream
- once obsequent stream, now consequent stream again
- resequent stream
- Drainage pattern like branches
- dendritic
- parallel lined drainage pattern
- trellis
- parallel, but branching
- rectangular
- streams go away from a central point
- radial
- streams flow to a point
- centripetal
- leading edge of incision
- knickpoint
- one stream captures another
- stream capture
- drainage divide shifts so that one river's drainage captures another
- Abstraction
- tributary captures the original trunk
- autocapture
- old valley that is left high and dry due to stream capture
- wind gap
- one meandering river meanders into another
- intercision
- gently sloping, concave upward, graded surface of erosion that cuts across rocks of varying resistance with a thin veneer of alluvum
- pediment