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149 Cards in this Set

  • Front
  • Back
Dating techniques
relative dating and absolute dating
relative dating
establishment of age of a feature relative to the age of another feature: original horizontality, superposition, cross cutting relationship
Original horizontality
Sediment were deposited in vast horizontal sheets
age equivalance of rock layers
strata from different places can be established using fossils
sequence of sedimentary rock layers-younger rocks are at the top and older rocks are at the bottom
cross cutting relationship
feature cutting through another feature must be younger than the feature it cuts through
absolute dating
used to establish the exact age of a feature-may date rock formation and rock metamorphsis
radiometric dating
use of constancy dcay rates of radionuclei to calculate year of their origin
half life
the constant time required for 1/2 of the amount of a parent isotope to decay into a daughter
commonly used isotopes
40K40Ar-1.3 billion 238U206Pb-4.5 billion
14C14N-5730 yrs-organic
Dating ranges
1/10-10x's the half life
tree ring dating
Precambrian Eon
4500 mya to 540 mya-most of earth history-rocks mostly in continental cratons-atomosphere little oxygen until phtosyntheic plants-early fossils prokaryotic bacteria and algae-stromatolites
Paleozoic Era
540-248 mya early, mid late, and end
Early Paleozoic
orgnisms diversity and abundance-trilobites and fishes, fossils
Mid Paleozoic
Fishes dominate, first land plants, and insect fossils
Late Paleozoic
Pangea formed early app mtn chain
End Paleozoic
massive extinciton of many marine animals
Mesozoic Era
248-65mya triassic, jurassic, cretaceous
Early mesozoic
break up of pangaea-triassic-gymnosperams and dianosaurs-first mammals
Late mesozoic
sierra nevada batholith, rocky mtns.
End of Mesozoic
massive extinction-perhaps meteorite impact in Yucatan
65 Mya-present-Early Mid Late
Early Cenozoic
Mammals and angiosperms become dominant
Mid Cenozoic
Late Cenozoic
Pleistocene-glaciation begins
Late Cenozoic Pleistecene/Holocene boundary
megafauna extinctions (wooly mammoth, giant sloth)
Global water balance
ocean contain most water on earth, ocean main source of percip, other (glaciers and groundwateR)
Run off
water flowing over the land surface rather than soaking in below ground
Largest freshwater reservoir available to humans
Groundwater Dist.
Zone of aeration, zone of saturation, aquitard, aquifer, perched water table
Zone of aeration
contains a mix of air and water in pore spaces
Zone of saturation
all pore spaces fille w/ water, top of zone is water table
rock material body that hinders water move.
rock material containing retrievable water-transmits water freely. unconfined/confined
Unconfined aquifer
not overlain by an aquitard
confined aquifer
both underlain and overlain by aquitards
Perched water table
zone of saturation above the regional water table creaed by an aquitard.
Groundwater movement
depends on porosity, permeability, water table slope-mm's to a few cm's per day
voume of por space in rock material
ability of a rock material to transmit fluid
Water table slopes
drop in elevation of the water table divided by the distance over which this drop occurs
Artesian flow
springs and wells that discharge water freely
Issues w/ groundwater
availability, pollution, land subsidence, groundwater mining
availability groundwater
number of houses using water
pollution of ground water
sewage leak in if too many houses close together
ground collapse due to excessive water mining
reason for extinction due to climate change-change in environment-human population-disease
Milan Kovitch hypothesis of Ice age
periodicy in 3 orbital characteristics-oribital eccentricity, axial tilt variation, and precession
Orbital eccentricity
10,000 yr cycle-changes in ellipticalness-low eccentricity less change in season
Axial tilt variation
22-24.5 degrees 41,000 yr cycle-low tilt less sesaonality
Northern Hemi tilted away from the sun-less seasonality 26,000 yr cycle
Moisture of NC
comes from Gulf of Mexico
plants take water from soil release into the air
Occurance of artesians
areas of tiled rocks enter ground flow down-build pressure because of aquifer bt two aquitards cause bubbling-drill through aquitard to get to aquifer
the physical breakdown and chemical alt. of rocks at or near the earth's surface
Mechanical/Physical weathering
breaking of rock into smaller pieces via natural physical forces w/o changin the rock's mineral comp.
Chemical weathering
chemical transformation of rock into one/more new compounds: almost always requires water
rock detritus at the sruface of the earth that has been weathered by physical and chemical, and biolic process so it supports growth of plants
Soil Horizons
A horizon, B horizon and C horizon which all develop together-layers do not indicate age
A horizon
mineral rich-organic water breakdown zone of loss which gets washed to B
B horizon
strongly red in NC-receives nutrients from A roots of plants lost at the end of B
C Horizon
unaltered parent material which forms the other layers
Karst Topography
Terrain w/ distinctive landforms and drainage arising from geater rock solubility in natural water than is found elswhere-create caverns/sinkholes-
Running Water
Most important agent of land surface changes. Organized within drainage basins-catchment, drainage divides, channel network,hillslopes
collecting area catches rainfall that runs to a particular stream
Drainage divides
drainage basin boundaries coincides w/ ridges separating one catchment from another
Channel Network
series of connected streams extending from headwaters to the point of outflow
sloping uplands that feed water to channel network
water in channels
different characteristics: discharge, velocity, stream incision, overbank flooding
volume of water moving through a channel at a given place per unit of time-wXdXv cubic meters/sec
Velocity variation
depth, gradient
Depth w/ velocity
greater depth reduces frinction with banks
Gradient w/ velocity
Slope of streambed-decreases downstream, streams cut down towards base level, lower limt of erosion-lowest near ocean
Stream incision
deepening of channesl by cutting down into bed-urban streams-deeper due to pavement
Flood levels
1.5 years, 50 years, 100 years-statistical probability not exact-go over flood plain
Zoning laws
based on 50-100 year flood levels
erosion and sediment transport
particle movement, size and rate
Particle movement
bedload, suspended load, dissolved load
mechanism for transport of sediments
Bed load
materials move along bed
suspended load
above bed never come into contact w/ bed-cause cloudy water
dissolve load
not see-ionic fully dissolved
Size and rate sediment move
proportional to flow velocity-silt and fine sand move easiest
Rivers and Floodplains
Sinuous/meandering which forms cutbanks and point bars
Point Bars
Inside bank of meandering stream higher bank
Cut bank
Outside bank of meandering stream-lower bank
formed when a meanders join
above the flood plain
Natural levee
deposit sediment forms higher bank
Braided stream
multiple interweaving channels-islands of sediment-higher gradient,higher sediment loads, coarse sediments, non-cohesive banks
Older floodplain surfaces left behind at higher elevations as a river incises downward-caused by cutting down of rivers-paired, unpaired
Paired terraces
caused by sudden climate change-tectonic plates
Unpaired terraces
gradual river incision-slow changes
sinking below sea level-sediment dposisits in large water bodies-water move from streams slowed causes coarse sediment to fall out
General glacier
occur anywhere there is incomplete melting of snowfall during warm season-as far south as N. Kentucky
When glaciation
high altitudes and latitudes
Ice processes form glaciers
snow-> high porosity firn->granular spherules glacial ice interlocking ice crystals w/ little pore space
Firn line
close to equilibrium line characterized by snow to dark-migrates up glacier during warm season-separates accumlation and ablation zone
Move mech of glacial ice
basal sliding, internal deformation
Basal sliding
sliding of the glacier over its bed
internal deformation
plastic flow-movement of ice via relative move. bt and within ice grains
Velocity characteristics of glaciers
velocity faster at the surface until brittle zone-can result in crevasses
Brittle zone
upper area won't undergo deformation b/c not enough weight will snap and break
breaks in brittle zone-may be snow covered
Ice Flow and Mass balance
accumulation, ablation
gain of glacial ice via percipitation
loss of glacial ice via melting and sublimination
net accumulation
accumulation is greater than ablation results in advance
net ablation
accumulation is less than ablatioin results in retreat
Alpine glaciers
confined to by valley walls-flow down hill
Ice Sheets and caps
not confined to valley walls-cover vallesy and ridge tops
Ice Sheets
largest glaciers-cover Greenland-2 miles thick
Ice Caps
Mass capping of portions of mtn ranges
Flows of non-confined
occurs down the gradient of ice surface from ares of thick to thin ice
Glacial erosion
abrasion, striation, plucking
drag across rock surface causing glacial polish
glacial striation
caused by boulders in glacier gouging in to rock surface
ice flosw oever rocks and freezing drawing rocks out and then taw leaving rock behind
Glacial landforms
erosion, deposition
trough, cirques, aretes, cols, horns, streamlined forms(finger lakes)
ice accumulation in high mtns forms valley glaciers form v cuts out u form melt and forms water falls then tributary valleys
Tributary valleys
are hanging valley share a sharp wall-arettes
bowl shaped depression @ the top of glacial valleys where ice flow starts-alpine
very tall triangual spikes formed by surrounding cirques
Finger lakes
formed by galcier carved out running across land-ice sheets
Glacial deposition
an ice conveyor belt-drift, till, outwash, erratics-
Stable glacier
results in piles of sediement-ablation and accumulation are equal-stagnant-forms end moraine
Glacial retreat
Accumulation is greater than ablation-sheets of till-forms a ground moraine
Glacial advance
Ablation is greater than accumulation-no apparent moraine
Glacial till
unsorted sediment deposits
unpredictable deposit of sediment-where it couldn't been formed
Lateral moraine
is a deposit of till that develops on the sides of valley glacier
medial moraine
formed by two lateral moraines
End moraine
is a ridge of till found at the terminus of a valley glacier.
is formed by blocks of ice that are separated from the main glacier - perhaps the ice front stagnated or retreated or perhaps ice blocks were washed out from the glacier during a glacier flood
are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them
Very easily dissolved w/ water
River erosion
creates relief-elevation variation in an area
Hillside anatomy
topslope, footslope, toeslope, upper
convexity, lower concavity, talus, scree
hillslope denudation
water and mass wasting
Mass wasting
the downslope movement
of rock debris in response to gravity water can be a component
Angle of Repose
the stable angle below which
unconsolidated material will cease to spontaneously slide.
(32-35 degrees for loose dry sand)
Major Types of wasting
Slumps Flows
mostly in soil; very slow-building problems
(land, rock, mud)
(coherent); mod.-fast
(mud, earth, debris) High water content; fast
(debris, snow) Dry; fast