Test 4 Material Flashcards
what is mass wasting
rock on unstable slopes has the potential to move downslope under the influence of gravity, important in mountain errosion
Subaerial (slow to fast)
creep, solifluction, slump, mudflow, debris flow, lahar, rockslide, debris slide, avalanche, debris fall
creep
slow gradual downslope movement on a slope
solifluction
in places where slopes are underlain with permafrost, causes a melted layer to flow down slopes in the brief summer thaw
slump
a slow-moving event which rock does not disintegrate but stays somewhat coherent
mudflow
or mudslide, a moving slurry of mud by heavy rain
debris flow
a slurry consisting of a mix of mud and pebble to boulder sized fragments
lahar
mudflow of volcanic ash and water from the melted snow
rock slide
a sudden movement of rock down a non-vertical slope
snow avalanche (dry)
formed when the snow mass contains no liquid water, tumbles as cloud of powder
snow avalanche (wet)
formed at warmer temperatures, move as a mix of solid and liquid water
rock avalanche
when the material in a rock/debris fall mixes with air and forms a turbulent cloud that races downslope
rockfall
occur when a mass free falls from a cliff, commonly happen along joints
debris fall
when debris free falls
talus
a sloping apron or rocks along the base of a cliff
three stages of mass wasting
- fracturing and weathering of substrate
- development of relief, provides a slope to move down
- an event that sets it in motion
resistance force
granular debris tends to pile up and produce the steepest slope
angle of response
the angle depends partially on the shape and size of the grains, which determine the amount of friction
what causes slope failure
shocks, vibrations, and liquefaction, changing slope loads, changing slope strength
identifying dangerous mass wasting regions
slump head scarf, tilted trees, piles of loose debris at base of hill, bumpy land, manmade features crack over time
preventing mass wasting
- revegetation, and regrading
- reducing subsurface water, prevent undercutting
- building safety structures
- controlled blasting of unstable slopes
the hydrologic cycle
circulation of earths water supply
sources of earths water
streams make up a small percentage of freshwater
forming streams
- begins as sheetwash
- sheetwash digs tiny channels called rills
- rills down cut, develop into streamflow
formation of drainage networks
streamflow increases as water is added, widen stream via erosion, over time nearby channels merge, smaller tributaries join a larger truck stream, change over time
patterns in drainage networks
often form geometric patterns that reflect the underlaying geography
common drainage patterns
dendritic, rectangular, trellis, radial, and deranged
drainage basin
land areas that drain into a specific system
divides
separation between basins by high topography
continental divides
separate flow into different oceans
permanent streams
water flows all year, at or below water table, humid/temperate, sufficient rainfall, lower evaporation, flow varies seasonally
ephemeral streams
do not flow all year, above water table, dry climates, low rainfall, high evaporation, flow mostly during flash floods
2 types of streamflow
laminar (slow) and turbulent (fast) flow
laminar flow
streamlines are parallel, no mixing between layers
turbulent flow
streamlines intertwine, complex mixing
factors that determine stream velocity
gradient (slope), channel characteristics (shape, size, and roughness), and discharge
discharge
volume of water moving past a point in a certain amount of time
gradient
vertical change over horizontal change, decreases downstream
channel characteristics
friction along sides and bottom of channel slow down water
what type of streams move faster
narrower streams
Channel discharge equation
Q (discharge) = VA (velocitycross-sectional area)
breaking and lifing
push of current breaks pieces of stream channel
abraision
sand floating in water grinds channel
dissolution
water dissolves minerals and carries them away
stream load
material being transported
competence
the max sized particles a stream can carry, high competence = large particles
capacity
total quantity of sediment a stream can carry
deposition
caused by a decrease in velocity
channel deposits
bars and braided stream
floodplain deposits
natural levees form parallel to stream channel by successive floods
alluvial fans
where a high gradient stream leaves narrow valley and then flattens out, slopes outward in a broad arc
deltas
forms when a stream enters the ocean or lake
stream landscape
narrow valleys and wide valleys
narrow valleys
V shaped, features: rapids and waterfalls, energy directed down
base level
the lowest point to which a stream can erode
types: ultimate (sea level), local (resistant rock layer)
wide valleys
streams near base level, energy is side to side, characteristics: meanders, floodplains
features of meandering streams
cut offs, oxbow lake, point bars, cut bank
incised meanders
meanders cut into steep narrow valleys, caused by drop in base level or uplift of region
terraces
remnants of former floodplains
floodplains
stream overflows bank depositing material on either side
floods
most common and destructive geologic hazard
causes of floods
abrupt, heavy rain or snow melt, long periods of rain, collapse of dam
types of floods
seasonal or flash
seasonal floods
gradually submerges, develop over hours or days
flash floods
water rises very quickly, only last few minutes to few hours
recurrence interval
average number of years between successive floods of a given size
annual probability
the likelihood that a flood of a given size will happen during any given year
flood control
artificial levees, flood-control dams, channelization
glaciers
thick masses of ice
types of glaciers
valley/alpine and continental/ice sheet
valley (alpine) glaciers
mountainous areas, flow down valley from an accumulation center
continental (ice sheet) glaciers
larger scale, flow in all directions, Greenland and antarctica
glacier formation
fluffy snow packs down into granular snow, snow recrystallizes into firn, firn fuses into interlocking ice crystals forming glacial ice
glacial movement
ice near valley floors and walls move slower than ice in the center
glacial ice movement
basal slip, and plastic flow
basal slip
beneath the glacier, entire ice mass slipping
plastic flow
within glacier, pressure causes ice to behave plasitcally
zone of fracture
occurs on top 50m of glacier, tension causes crevasses to form
glacial surge
rapid glacial movement
sections of a glacier
zone of accumulation, zone of wastage, glacial budget
zone of accumulation
where glacier forms
zone of wastage
loss of glacier
glacier budget
balance between accumulation and wastage
glacier erosion
plucking/bulldozing and abraision
plucking
glacial ice freezes in cracks and pulls rock loose
abraision
rocks within ice polish surface, produces glacial striations
bulldozing
glacier pushes or shoves material
U shaped troughs
valleys scoured by glaciers
hanging valleys
tributary valley whose floor is at a higher level than the main valley
cirques
bowl shaped depressions that form beneath the upper end of glacier
aretes
thin ridge formed by the erosion of two cirques
horns
steep walled pyramidal peaks
valleys for rivers and glaciers
U shaped = glaciers, V shaped = rivers
fiords
former glacial valley drowned by the sea
till
sediments deposited directly by ice
stratified drift
sediments deposited by glacial meltwater
moraines
ridges made of till
drumlins
smooth elongated parallel hills made of till, steep side faces direction ice came from
outwash plains
broad surface deposited by meltwater leaving glacier, kettles
ice contact deposits
deposited by meltwater flowing over motionless ice, kames and eskers
ice age
2-3 million yrs ago, ice cover 30% of land, effects: migration, changes in stream course, change in seal level, climate change
causes of glaciation
plate tectonics, variations in the earths orbit
desert
arid region where evaporation exceeds precipitation
characteristics of deserts
cold or hot, dry (less than 25cm of rain), high evaporation rates
subtropical desert
low latitude deserts around tropics of cancer and Capricorn
rain shadow desert
when moist marine air moves inland and meets a mountain range, dry air descends on the opposite side of mountian
continental interior desert
at mid latitudes, far enough inland that air is low in moisture
coastal desert
generally on western edges of continents
polar desert
at extreme latitudes, snow dunes can form in areas with slightly more moisture
desert rainfall
brief heavy showers, flash floods common, most erosion by running water
wind in desert
not confined to channels, can spread over large areas
surface load
skipping and bouncing along surface (sand sized particles)
suspended load
sediment floating in air (silt and clay sized particles)
wind abrasion
the impact of sand grains on an object
dunes
mounds of sand, asymmetrical, slow migration in direction of wind
dune geometry
barchan, longitudinal, transverse, parabolic, barchanoid, and star
playa lakes
when excess water is not absorbed into the ground after an intense rainstorm
playa salt pan
forms when a playa lake evaporates
desert varnish
iron and manganese oxide created from dust, moisture and micro organisms
mesas, buttes and chimneys
erosional features of progressively smaller size
global change
transformations or modifications of both the physical and biological components of the earth system
unidirectional change
one direction and never repeats, Ex: evolution
cyclic changes
happen often and over and over again, Ex: rock cycle, Wilson cycle
greenhouse gasses
CO2 and methane, key rolls in controlling earths climate
Climate change natural or human
modification to greenhouse gasses happen naturally over time but humans are effecting it to
approaches to studying climate change
measure past climate change to document the magnitude of change
use models to predict changes
paleoclimate
climatologists look at sedimentary record, paleontological evidence and growth rings
Oxygen Isotope ratios
ratio of O18 to O16 in glacial ice gives indication of temperature at which the ice formed
greenhouse
times in earths past where it was warmer than today
ice house
times in earths past when it was colder than today
how many major icehouse periods
5
causes of long term climate change
position of continents, volcanic activity, tectonic uplift, formation of fossil fuels, life evolution
short term climate change causes
fluctuations in solar radiation, changes in surface albedo (reflectivity), changes in earths Milankovitch cycles, changes in volcanic emission, changes of greenhouse gas concentration, changes in ocean currents
catastrophic climate change
happens instantly, result of volcanic eruptions, meteor impacts
mass extinctions
large number of species rapidly disappear, caused by catastrophic climate events
when did human population reach 1 billion and 2 billion
around 1850, took only 80 years to double it
changes to landscape
using up resources at an alarming rate
changes to ecosystems
rainforest disappearing at 2% each year
