Geomorphology Exam 2
Terms
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- Pediment Pass
- pediment with no residual knob left; only flat, gently sloping surface
- Alluvial fan
- landform formed as a stream exits an area of high relief and enters a broad flat plain.
- Bajada
- Flat depositional surface where many individual alluvial fans meet.
- Playa
- dry lake bed
- Delta
- triangular shaped protuberance in the shoreline which forms when a river meets a large body of water.
- Cycle of Erosion
-
Youth- steep
Mature- less steep
Old Age- flat - Peneplane
- Old-age flat erosional feature is the END PRODUCT of cycle erosion
- Lateral Planation
- meandering river goes back to the process of meandering back and forth flattening out an area.
- Fluvial terraces
- formed by something perturbing the system resulting in incision leaving areas to the side outside the areas of erosion
- Cut-in bedrock terrace
- erosional surface
- Fill terrace
- constructed by deposition, river incises into new level and then fills.
- Cut and fill terrace
- river meanders back and forth creating deposition, then cuts down through it and, while cutting, fills it back up.
- Cyclic erosional surface
- similar to a pediment, relics of former flood plain, now dissected.
- Stripped strctural surface
- surface formed by selective stripping of the low resistance surface from high resistance rocks leaving behind a low relief plane.
- Entrenched meander
- due to uplift around a meander, the meander is stuck in it's course
- Porosity
- volume of void space/total volume
- 3 Spaces for Porosity
-
Intergranula spaces
Fractures
Solution Cavities - Primary porosity
- poristy before any changes to a rock (fractures)
- Secondary porosity
- porosity after alteration to a rock
- Packing
- how tightly packed grains are within a rock
- Sorting
- relative size of grains within a rock
- Permeability
- ease at which fluids travel through a rock
- Specific yield
- ratio of volume of water that is drained by gravity from saturated sediments to the total volume of the material
- Specific retention
- ratio of volume of water retained after draining by gravity to total volume
- Porosity =
- specific yield + specific retention
- Hydraulic conductivity
- volume of water at a given viscosity that will move in a porous medium in a unit time under a unit hydraulic gradient through a unit area measured at right angles to the plane
- Darcy's law
-
Q= PIA
Q= discharge
P= hydraulic conductivity (m/s)
I= hydraulic gradient
A= cross-sectional area (m^2) - Water table
- upper surface of zone of saturation
- Zone of saturation
- subsurface area in which all porosity is filled
- Aquifer
- geologic unit that can store and transmit economic quantities of water
- Unconfined aquifer
- extends continuously from a land surface downward through a material with high permeability
- Confined aquifer
- bound both above and below with impermeable or nearly impermeable layers
- Artesian aquifer
- aquifer under enough pressure that, if allow to connect to surace, water would flow freely to surface
- Thermal spring
- groundwater becomes heated to high temperatures due to a heat source in the surface
- Karst topography
-
formed by dissolution
characterized by:
Sinkholes
Caves
Underground drainage - Types of Sinkholes
-
Solution sinkhole
Collapse sinkhole - Uvala
- compound sinkhole
- Polje
- large closed depression with flat alluvial fill
- Karst lake or Sinkhole Pond
- Karst lake intersects the groundwater table
- Solution chimney
- dissolving of limestone walls along fissures or bedding planes that are structurally controlled
- Vertival shafts
- circular cylinders with vertical walls that cut across fissures and bedding planes
- Disappearing stream
- river flows into karst features underground
- Karst valley
- valley where large percent of drainage is underground
- Dry valley
- remnant valley with all present drainage underground
- Pocket valleys
- fluvial valley that abruptly ends at a sinkhole
- Blind valleys
- valley flows away from a sinkhole
- Coast of submergence has...
- lots of estuaries
- Tidal flat
- areas that are submerged during high tide (mud-flat)
- Coral reefs
- predominantly found in temperatures between 77 and 86 degrees Fahrenheit
- Darwin
- first to model how an atoll (ring of reef around a lagoon) formed
- Fringing reef
- form around a seamount (less than 60m)
- Mangroves
- big integrated root system of trees captures sediment
- Glacier
- masses of ice or granular snow formed by compaction or recrystallization of snow lying largely or wholly on land and showing evidence of past or present movement
- Firn
- line between snow and ice (recrystallized snow)
- Pressure melting
- under great pressure, ice can melt and still have temerature of <0 degrees C
- Regelation
- melting and refreezing due to changes in pressure
- Glacial Movement Mechanisms
-
Basal sliding
Plastic flow
Compressive flow
Extending flow
Crevasses - Basal sliding
-
glacier slides over it's bed
meltwater is extremely important - Plastic flow
-
Intergranular shifting- movement taken place by rotating of crystal grains within a glacier
Intragranular shifting- crystals of ice are sheared (break parallel to movement)
Recrystallization- pressure melting important- ice melts and then refreezes down-slope - Compressive flow
- decrease veolicty, ice thickness