Exam 2

Geography 210 with Splinter at University of Wisconsin - Whitewater

About this deck

By: Cally Kretchmer
Textbook:

Introducing Physical Geography
Created: 2011-02-23
Size: 82 flashcards
Views: 15

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Mass movements

weakens surface rock and makes it more susceptible to pull of gravity. Can be:

Dry or wet

Slow or fast

small or large

free-fall or gradual

Gravity

driving force for when mass movements occur.

mass movements

function of a driving force, a resisting framework and time. TIME is key variable.

*If driving force is greater tan resisting framework = failure.

Classes of mass movements

Mass movements occur when a geomorphic threshold is exceeded:

Falls and Avalanches

landslides

flows

creep

Rock fall

volume of rock that falls through the air and hits the surface.

Avalanches

mass of falling and tumbling rock, depris, and soil.

Landslides

sudden rapid movement of mass of regolith or bedrock that is not saturated with moisture

Translational slides

movement along a planar surface roughly parallel to angle of slope

Regolith

partially weathered rock overlying bedrock.

Colluvium

weahered material moved to base of slope.

Alluvium

lie beneath valley

Madison River Landslide

1959

7.5 on Richter scale

Land was displaced 21 feet at its maximum extent

Tranlational slides

movemet along a planar surface roughly parallel to the angle of the slope.

Madison Canyon example.

Rotational slides

occurs when surface material moves along a concave surface. Ex. Slump- when small block of land shifts downward.

Flow

When moisture content of material is high.

Earth Flow

Fluid Flow

Creep

perisistent, gradual mass of movement of surface soil. Particles are lifted by expansion of freezing water and moved downslope when ice melts.

weathering

inplace physcial disintegration and chemical decomposition of rocks at or near the earths surface.

Physical (Mechanical weathering)

Chemical weathering

Mechanical weathering

Frost action

salt crystal growth

unloading or exfoliation

biological activity

Weathering:

weathered rock physically disintegrates to sediment.

Frost Action

repeated freeze-thaw cycle that occurs in cracks of rocks

Liquid water

expands approx. 9 % when freezes

Frost Action:

common feature of frost wedging is a talus slope.

Talus slope

material is angular and poorly sorted because it as not moved very far.

(Most common feature of frost wedging)

Frost wedging:

common features are poholes, cracks in sidewalks and buckled roads.

Salt Crystal Growth

growth as water evaporates crystals grow and enlarge, exerting a force great enough to spread apart individual mineral grains and break apart rock.

Unloading or exfoliation

outer layers expand more than underlying rock and separate from the rock body

ex. stone mountain, half dome

Sheeting

general process that produces exfoliation domes

-characterized by splitting off of slablike sheets of rock

-occurs because of reduction in pressure when overlying rock is eroded away

-onionlike layers

Biological activity

plant roots, burrowing animals, humans, etc.

Increased rates of weathering

mechanical weathering makes chemical weathering more efficient by increasing surface area.

-Greater the surface = more area for chemical attack.

Chemical weathering

Environment; principle agent = water

Spheroidal weathering

occurs when water attacksthe angular edges of rock and rounded edges develop

rate of chemical weathering

increase wih temperature and precipitation.

Pure water (pH-7)

non-reactive

water with dissolved ions

will activate chemical reactions in rocks and minerals

atmospheric carbon dioxide

easily dissolved in rainwter and forms weak carbonic acid

Landscapes

-erosional

-depositional

Fluvial

describes stream related processes and resultant forms

Fluvial transport

movement of material by running water

Deposition

sediments are laid down because velocity of water can no longer move sediment

Alluvium

Deposits made by streams on river beds, aluvial fans, floodplains, etc.

John Wesley Powell

proposed idea of base level

base level

level below which a stream cannot erode its valley

Tributary

starting place (kickapoo river is tributary of wisconsin river)

Drainage basins

an area that contributes overland flow and groundwater to a specific stream

(every stream has drainage system)

Continental divides

high drainage divides that separate mountains and highland regions

Internal drainage

streamwater finds way to larger rivers and oceans or water leaves basin by evaporation or subsurface flow

Drainage density

calculated by dividing total stream length by the area of the drainage basin

Drainage pattern

arrangement of channels in an area

variables that influence drainage patterns

regional steepness, rock resistance, climate, hydrology, landscape relief, geologic structure.

Drainage patterns

dendritic

trellis

radial

parallel

deranged

drainage patterns: Dendritic

most common, forms where there is a homogeneous rock type

Drainage patterns: Trellis

characteristic of regions that have dipping or folded topography

Drainage patterns: radial

occurs when streams flow off a central peak or dome such as volcanic mountains

Drainage patterns: parallel

Common on steep slopes

Drainage patterns: deranged

areas that have disrupted surface patterns with no clear geometry in the drainage ( glaciated regions, karst topography)

Discharge

Q=wdv

-As Q increases, some combination of channel width, depth and velocity increases

-velocity increases downstream although the gradient of the stream decreases

-resistance with stream bottom decreases downstream

Stream erosion

a streams erosion turbulence and abrasion carve and shape landscapes as it flows

Erosion

-Hydraulic

-Abrasion

-stream velocity determines rates of erosion and deposition

Hydraulic action

work of flowing water alone, which loosens and lifts particles off the stream bed and from banks

Abrasion

particles mechanically erode the stream bed and stream banks

four processes transport eroded material:

-solution

-suspension

-saltation

-traction

Solution

dissolved load, includes chemical solution derived from minerals such as limeslone, dolostone.

Main contributor of material in solution is chemical weathering

Suspension

fine-grained pieces of weathered rock

-turbulance keeps particles in suspension

-finest particles deposited when velocity is nearly 0

Saltation and Traction (Bedload)

bouncing, rolling or sliding particles downstream

Ex: Imbrication- packing of particles of similar size)

aggrading

when load of stream exceeds a streams capacity to transport sediment

braided stream

with excessive sediment, streams develop complex and interconnected channels.

Streams two types of flow:

-laminar

-turbulent

Laminar flow:

streamlined flow of water in which fine particles move along in parallel paths. Occurs where water is deep and channel surface smooth

Turbulent flow:

occurs in shallow streams or where stream is rough. Flow propels sand, pebbles and boulders to be transported

Velocity

Velocity is greatest in center just below surface

Velocity along a meander

greatest on outside of meander, produces greatest amount of erosion, especially where vegetation lacks

Ex. Cut-bank

velocity along a meander

slowest on inside of meander, deposition of sediment

Ex. Point Bar

Meander loops lead to oxbow lakes

-erosion on outside of meander creates neck

-neck narrows and stream erodes through neck

-stream follows new route and becomes straighter

-old portion of stream becomes ox-bow lake

Meander scars

ox-bow lakes that fill in with sediment

Sinuosity

never less than 1

Straight sinuosity= 1-1.5

Meandering sinuosity= > 1.5

Braided stream- sinuoism not applied

Head water streams on mountains tend to be straight

Stream gradient

longitudinal profile of a stream that describes changes from upstream to downstream

nickpoints

located along longitudinal profile where there is an abrupt change in gradient

ex. waterfalls, rapids

Natural leeves

area adjacent to stream that are created when stream overflows and deposits sediment along bank of channel.

Stream terraces

abandoned floodplains- created when streams entrench into the floodplain and scour downward

Flood recurrence intervals

High probability/ low magnitude

low probability/high magnitude

About this deck

By: Cally Kretchmer
Textbook:

Introducing Physical Geography
Created: 2011-02-23
Size: 82 flashcards
Views: 15

About StudyBlue

“I have been getting MUCH better grades on all my tests for school. Flash cards, notes, and quizzes are great on here. Thanks!”
Kathy