Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/212

Click to flip

212 Cards in this Set

  • Front
  • Back
Groundwater
water found in sediment & fractures in bedrock

-largest freshwater resource available to humans (makes up majority of non-frozen freshwater) (second after glaciers when including all freshwater)

-sustains streams during dry periods
[stores rainwater]

-makes sinkholes and caves (removal of limestone)

-moves only a few CM / day

-powered by energy from gravity
--->allows water to move from where h2o table is high to where it is low
rate of exchange for groundwater
v
rivers
rate of groundwater exchange:
280 YEARS

rate of exchange for rivers:
11 DAYS
[w/o rain river would run dry in 11 days]
distribution of groundwater
*more steep = less groundH2O

ZONE OF AERATION:
1)belt of soil moisture
2)capillary fringe
{can't be pumped into wells bc clings to rock}

ZONE OF SATURATION:
1)WATER TABLE
(upper limit of saturation zone & ground water)
belt of soil moisture

term
the water in the near surface zone

-doesn't travel far due to molecular attraction at surface --->film on soil particles
*where roots and organic matter are
zone of saturation

term
where all pore spaces are completely filled w/H2O

-water within zone of saturation = GROUNDWATER!

-the upper limit = water table
capillary fringe

term
where "groundwater" is held by surface tension in passages between grains of soil/sediment
zone of aeration

term
the area above water table including ccapillary fringe and belt of soil moisture

-water here can't be pumped by wells b/c it clings to rock/soil
water table variations
-depth is highly variable
-varies seasonally & from yr to yr due to changes in rainfall

-not flat
-->resembles surface topography
-moves slowly & "piles up" beneath high areas
(if rain ceased, H2O"hills" would decrease and reach valley level)
"gaining streams"
streams gain water from groundwater

-water table must be at higher elevation than surface of stream

*most common*
"losing stream"
stream loses water to groundwater

-water table elevation must be lower than surface of stream
porosity influencing groundwater
porosity = % of total volume that consists of pore spaces
permeability
the ability to transmit a fluid

-smaller the pore spaces slower water moves

groundwater divided into:
1)specific yield
2)specific retention
specific yield
the portion of groundwater that will drain under influence of gravity

*indicates how much water is actually available for use

[ex. clay's porosity = high; spaces small = h2o can't move thru it = LOW specific yield]
specific retention
groundwater that's retained as film on surfaces and in tiny openings

*indicates how much water is bound in material
aquitards
impermeable layers hindering or preventing h2o movement

*CLAY*
aquifers
permeable rock that transmits groundwater freely

*SANDS & GRAVELS*
Spring
natural outflow of groundwater resulting from when water table intersects earth's surface

also result when aquitard blocks downward movement and forces it laterally ->spring results where bed is outcropped

also a small aquitard can prevent a portion of water intercepted creating localized zone of saturation & a PERCHED water table
perched water table
localized zone of saturation above the main water table
-->created by impermeable layer [aquitard]
hot springs
result from grounwater circulated and heated at great depths

*water = 6-9*C warmer than avg air temp

-source of heat for most = cooling igneous rock
---->most in WEST!
Geysers
intermittent hot springs
-water ejected then steam
-occur where extensive underground chambers exist w/i hot igneous rock

PROCESS:
-cool groundwater enters chamber
-heated by surrounding rock
-great pressure prevents it from boiling
-heating of water causes expansion
-some forced out at surface
-loss of water reduces pressure on remaining water
-->lowering the boiling point
-portion of h2o deep w/i chamber turns to steam and geyser erupts

(groundwater heats, expands, turns to steam, erupts)
aquifer
underground bed / strata that yields water
Well
hole penetrating into the zone of saturation

-to ensure continuous water supply hole must penetrate below the water table
drawdown
the effect of the water table lowering around a well when water is withdrawn from it

-decreases w/ distance from well

-results in a depression in the water table (a cone of depression)
cone of depression
a depression in the water table resulting from the drawdown effect from a well

-->increases hydraulic gradient near well --> water flows more rapidly toward opening

-->causes nearby shallow wells to become dry
problems associated w. groundwater withdrawal
1)treating groundH2O as nonrenewable
-h2o available to recharge aquifer often less than amt being withdrawn

2)subsidence {to sink lower than normal levl}
-ground sinks when h2o pumped out faster than its recharged

3)saltwater contamination
-saltwater is drawn into wells, contaminating supply
-major problem in coastal areas

-freshwater less dense than saltwater...floats on top
-water table 40x greater below sea level than above sea level
-excessive pumping lowers water table ==> the bottom of freshwater zone rises by 40x that amount

*also as more surface is covered by parking lots/buildings/etc
--->reduction in h2o infiltration
groundwater contamination
sewage = common source
-increasing # of septic tanks
-can become purified after passing thru few dozen meters of sand or permeable sandstone
-gravel and other really permeable aquifers have large pores thus groundH2O can travel LONG distances w/o being cleansed

-a sinking well -->cone of depression-->steeper slope-->faster movement of water--->
*Original Slope Can Be Reversed!*
*faster movement of water can also allow for less time for water to be purified*

-fertilizers
-pesticides
caverns
created when slightly acidic groundwater dissolves limestone in zone of saturation
groundwater dissolves rock when...
groundwater contains carbonic acid (when rainwater dissolves carbon dioxide)
-carbonic acid reacts w/calcite in limestone
dripstone
(travertine) - found w/i caverns

-calcite deposited as carbon dioxide evaporates from water

-collectively called speleothems
speleothems
-the various dripstone features found in caverns
-no two exactly alike

types:
1)stalactites
2)stalagmites
stalactites
type of speleothem

-hang from ceiling
-carbon dioxide escapes from drop and calcite precipitates
-hollow limestone tube created [SODA STRAW]
stalagmites
type of speleothem

-form on floor of cavern and reach toward celing
-don't have central tube
-more massive

*given enough time stalactite and stalagmite can form a column
karst topography
landscapes that have been shaped by dissolving forces of groundwater

-areas typically have irregular terrain punctuated with sinkholes
-lack surface drainage (streams)
--->after rain water funneled below ground thru sinks -- flowing through caverns until reaching the water table
sinkholes (sinks)
depressions
formed by:
1)gradually without physical disturbance ->limestone just below soil dissolved by freshly charged rainwater
-shallow w/gentle slopes

2)abruptly when roof of cavern collapses under its own weight
-steepsided & deep
Glaciers
thick mass of ice originating on land from accumlation, compaction, & recrystallization of snow
-cover ~10% of earth's land surface
-h2o stored as glacial ice for tens, hundreds, thousands of years
-powerful erosional force
--->accumulates, transports, deposits sediments
(they FLOW)
Valley / Alpine
Glaciers
-exist in mountainous areas
-flows down valley from accumulation center at head

-advange a few CM / day
-stream of ice bounded by rock walls
-widths usually small compared to length
Glaciers
thick mass of ice originating on land from accumlation, compaction, & recrystallization of snow
-cover ~10% of earth's land surface
-h2o stored as glacial ice for tens, hundreds, thousands of years
-powerful erosional force
--->accumulates, transports, deposits sediments
(they FLOW)
Valley / Alpine
Glaciers
-exist in mountainous areas
-flows down valley from accumulation center at head

-advange a few CM / day
-stream of ice bounded by rock walls
-widths usually small compared to length
Formation of glaciers
-form in areas where more snow falls in winter than melts in summer

STEPS:
-air infiltrates pores in snow crystals
-water vapor condenses
-->snowflakes become smaller, thicker, spherical
(& large pores disappear)
-air has been forced out and snow has recrystallized into a denser mass of small grains [FIRN]
-more snow = pressure increases
-->when thickness exceeds 50 M weight fuses firn into solid mass of interlocking ice crystals
-> GLACIAL ICE

*snowflakes smaller, thicker, spherical; air forced out; recrystallized into grains -FIRN; thickness exceeds 50 M -becomes glacial ice
Firn
granular recrystallized snow

-denser mass of coarse grains
w. consistency of sand
transformation of snow to ice
snowflake

granular snow

firn

glacial ice
2 types of glacial "flow" (movement)
1) plastic flow

2) basal slip
plastic flow
-movement WITHIN the ice
-ice behaves as brittle solid until pressure exceeds 50 M then behaves as plastic (silly putty)

-glacial ice = molecules stacked on eachother
-bonds between layers weaker than bonds w/i layers
-->LAYERS SLIDE OVER ONE ANOTHER
basal slip
-entire ice mass slips on ground
-most glaciers flow by this process
-occurs in discrete "JUMPS"

-meltwater acts as hydraulic jack / lubricant helping ice over rock

-temperatures can be increased by friction from plastic flow --> glacier moves by both plastic flow & basal slip
zone of fracture
uppermost zone
-top 50 M (can't move by plastic flow)
-brittle
-carried along "piggyback" style by ice below
-when glacier goes over irregular terrain the zone is subjected to tension, creating fractures
-->cracks/ crevasses
crevasses
cracks that form in zone of fracture when subjected to tension from moving over irregular terrain
-can extend to 50 M
(below 50 M plastic flow seals them off)
basal slip
-entire ice mass slips on ground
-most glaciers flow by this process
-occurs in discrete "JUMPS"

-meltwater acts as hydraulic jack / lubricant helping ice over rock

-temperatures can be increased by friction from plastic flow --> glacier moves by both plastic flow & basal slip
zone of fracture
uppermost zone
-top 50 M (can't move by plastic flow)
-brittle
-carried along "piggyback" style by ice below
-when glacier goes over irregular terrain the zone is subjected to tension, creating fractures
-->cracks/ crevasses
crevasses
cracks that form in zone of fracture when subjected to tension from moving over irregular terrain
-can extend to 50 M
(below 50 M plastic flow seals them off)
basal slip
-entire ice mass slips on ground
-most glaciers flow by this process
-occurs in discrete "JUMPS"

-meltwater acts as hydraulic jack / lubricant helping ice over rock

-temperatures can be increased by friction from plastic flow --> glacier moves by both plastic flow & basal slip
zone of fracture
uppermost zone
-top 50 M (can't move by plastic flow)
-brittle
-carried along "piggyback" style by ice below
-when glacier goes over irregular terrain the zone is subjected to tension, creating fractures
-->cracks/ crevasses
crevasses
cracks that form in zone of fracture when subjected to tension from moving over irregular terrain
-can extend to 50 M
(below 50 M plastic flow seals them off)
rate of glacial movement
-several meters / day
-valley glaciers experience friciton on sides --> rate of flow greatest in center
-can experience surges
surges
periods of extremely rapid movements then returning to normal rate
-as much as 100x normal rate

-could be caused by increase water pressure reducing friction & increasing basal slip
zone of accumulation
where snow accumulation and ice formation occur

-->outer limits = snowline
snowline
the outer limit of the zone of accumulation

-elevation varies greatly
(polar regions @ sea level, tropical regions @ high elevations)
zone of wastage
beyond the snowline
--where there is a net loss to the glacier
(snow from previous winter melts, as does some of glacial ice)

wastage due to
1)MELTING
2)CALVING
calving
occurs in zone of wastage

-large pieces of ice break off the front of the glacier

-responsible for icebergs (when near ocean/lake)
-->icebergs SLIGHTLY less dense than water = 80% mass underwater
glacial budget
the balance between accumulation @ upper end and loss @ lower end

-if accumulation exceeds ablation the glacial front advances until ablation and accumulation are balanced

-if ablation exceeds accumulation the ice front will retreat & zone of wastage diminishes
(although ice within glacier still flows forward)
->shrinks from both ends
ablation
the loss at the lower end of the glacier
(in zone of wastage)
glacial erosion
capable of great erosion & transport, more than any other erosional force
(& much faster)

-ice doesn't allow debris to settle out like streams & such

Erode in 2 ways:
1)PLUCKING
2)ABRASION
Plucking
-the lifting of rocks

-loosens and lifts rock incorporating them into ice
-happens when meltwater penetrates cracks in bedrock beneath glacier and freezes
Abrasion
rocks w/i ice act as sandpaper to smooth/polish rock below

-pulverized (powdered) rock produced = rock flour
rock flour
when rocks in bottom of glacier produce pulverized rock / rock powder

-->can cause glacier to appear gray / milky

{PRODUCED BY GLACIAL ABRASION - friction}
glacial striations
scratches & grooves gouged into the bedrock

-gives clues to direction of ice flow

-caused by large rocks in ice @ bottom of glacier

{PRODUCED BY GLACIAL ABRASION - friction}

*doesn't always do this however.... can also polish the rock beneath
landforms created by glacial erosion
LIST
glacial trough
truncated spurs
hanging valleys
pater noster lakes
cirques
tarns
fiords
aretes
horns
GLACIAL TROUGH

(landform by glacial erosion)
the U shaped broader/deeper valley

-changes the V-shaped valley created by streams into U-shaped trough
-straightens the valley
TRUNCATED SPURS

(landform by glacial erosion)
triangular shaped cliffs

-created by the removal of spurs of land extending into glacial valley
HANGING VALLEYS

(landform by glacial erosion)
valleys left standing above the main glacial trough

-due to the fact that deepness of glacial erosion depends on thickness of ice
-valleys feeding into main trough not as deep
PATER NOSTER LAKES

(landform by glacial erosion)
bedrock depressions created by plucking *when they're filled with water!*
CIRQUE

(landform by glacial erosion)
bowl-shaped depression @ head of the glacial valley

-the focal pt of growth bc where snow accumulation & ice formation occurs
-begin as irregularities in mountainside & enlarged by frost wedging and plucking
-often occupied by a tarn
TARN

(landform by glacial erosion)
-small lake
-often occupies cirques
FIORDS

(landform by glacial erosion)
-deep
-steep sided
-inlets of sea
-@ high latitues
--where mtns adjacent to oceans
-DROWNED GLACIAL TROUGHS
--result of sea level rising after ice age

-depths can exceed 1000 M
ARETES

(landform by glacial erosion)
-sharp edged ridges
-carved by valley glaciers
-cirques exist on opp sides of a divide
-->as cirques grow the divide reduced to a narrow knifelike structure
HORNS

(landform by glacial erosion)
-pyramid like peaks
-carved by valley glaciers
-produced by groups of cirques enlarging and converging, producing an isolated horn
Glacial Drift
term for all sediments of glacial origin
-glacial deposits consist primarily of mechanically weathered rock (with little / no mechanical weathering)

2 types:
1)TILL
2)STRATIFIED DRIFT
TILL

(glacial drift)
material deposited directly by ice

-typically unstratified & unsorted!

*landforms made by till::
-moraines
-drumlins
STRATIFIED DRIFT

(glacial drift)
sidiments laid down by glaical meltwater
Glacial erratics
boulders found in till

-know they've been transported bc different from bedrock below
Moraine
layers or ridges made by glacial till

TYPES:
[made by alpine glaciers]
-lateral moraine
-medial moraine
[other types]
-end moraine (terminal or recessional)
-ground moraine
lateral moraine
ridges of till paralleling sides of the valley
-made by alpine glaciers

-ice erodes sides of valley & debris is collected on edges of moving glacier
-ice melts & debris is dropped next to valley walls
medial moraines
dark stipes of till within ice stream
-created by alpine glaciers

-when two alpine glaciers coalesce to form single ice stream
--till once on sides of each glacier joins to form single dark stripe of debris within newly enlarged glacier

*proof that glacial ice moves
End Moraine
ridge of till that formed at terminal end of glacier

-deposited when there is equilibrium between ablation & accumulation
-->ice is melting at end but ice flow continually deposits more sediments

TYPES:
1)terminal moraine
2) recessional moraine
terminal moraine
-type of end moraine

-marks the limit of glacial advance
recessional moraine
-type of end moraine

-end moraines that were created as the ice front OCCAIONALLY stabilized during retreat
(ablation & accumulation were balanced in different places along retreat)

*difference between terminal moraine & recessional morain = relative positions*
DRUMLINS
smooth elongated parallel hills
-COMPOSED OF TILL

-steep side faces direction ice advanced FROM
-gentler slope points in direction ICE MOVED

-occur in clusters (drumlin fields)
4 major stages in ice age
1) Nebraskan

2) Kansan

3) Illinoian

4) Wisconsinan
ICE AGE
ice covered ~30% of earth's land area

-had 20 glacial/interglacial cycles (occuring every 100,000 yrs)

-most major glacial stages occured during
PLEISTOCENE EPOCH

-began 2-3 ma ago
ice sheets
exist at much larger scales
-low solar radiation @ poles make them possible

-2 @ PRESENT:
1) GREENLAND ICE SHEET [N pole]
2)ANTARTICA ICE SHEET [S pole]

-aka continental ice sheets

-ice flows out in all directions from a snow accumulation center
how much of world's H2o is in glaciers?
~ 2 %
the antartic ice sheet
(#'s)
80% world's ice
65% of earth's freshwater

if melted, sea level rise 60 - 70 M
indirect effects of ice age
-as ice advances & retreats animals/plants forced to migrate
-change courses of rivers
-upward rebound of crust
(raising after the downwarping {curstal subsidence} from heavy ice)
-->up and in now rather than down & out

-during ice age sea level ~ 100 M lower than today
-climatic changes (ice age = response to significant climate changes)
-during pleistocene epoch = "wetter climate" creating pluvial lakes
any successful theory of glaciation has to account for
-cause for onset of glacial conditions
-cause of glacial/interglacial periods during pleistocene epoch
tillite
deposits indicating earlier glaciations (prior to ice age)
PLATE TECTONICS

as a cause for glaciation
-supercontinent was located at latitudes far south of present positions
-(OR, earlier) ice ages occured when continents in tropical latitudes were carried toward poles

-most commonly accepted


-changes in ocean circulation altered heat/moisture (& in turn CLIMATE)

*ALL OCCUR OVER VAST SPANS OF TIME - SCALE OF MILLIONS OF YEARS*

->*DOES NOT EXPLAIN ALTERNATING GLACIAL/INTERGLACIAL PERIODS*
MILANKOVITCH HYPOTHESIS

as a cause for glatiation
-variations of incoming solar radiation due to variations in earth's orbit

1)ECCENTRICITY
-variations in shape of orbit around sun
2)OBLIQUITY
-changes in angle of axis
3)PRECESSION
-wobbling of earth's axis

-->can lead to milder winters & cooler summers

*Explains glacial/interglacial periods (on scale of thousands of yrs not millions)*

***accounts for changes in climate over past 300,000 yrs

--called milankovitch cycles
eccentricity
the shape of earth's orbit around sun
obliquity
change in angle of earth's axis
precession
wobbling of earth's axis
structural geology
studies architecture of crust & processes responsible for deforming it
rock structures contain
oil fields

ore deposits
deformation
all changes in size shape orientation and position of a rock mass

-most deformities occur along plate margins

-occurs from tectonic forces

-includes:
1)STRESS
2)STRAIN
Stress
force / area

(measure of how concentrated the force is)
differential stress
stress applied unequally in different directions

INCLUDES:
1)compressional stress
2)tensional stress
3)shear stress
compressional stress
differential stress that shortens a rock body
-plate collisions
-shortens & thickens crust by folding / flowing / faulting
Tensional stress
differential stress elongates or pulls apart rock unit
-plates are rifted - divergent plate boundaries
-lenthens rock bodies
shear stress
-often occurs on closely spaced parallel surfaces of weakness (bedding planes)

-similar to slipage between playing cards
strain
changes in shape or size of rock body from stress
how rocks deform
rocks subjected to stresses greater than their own strength

deform BY:
1)fracturing
2)folding
3)flowing
steps of rock deformation
1)first deform elastically
-elastic deformation
(recoverable)
2)after elastic limit surpassed it either FLOWS (ductle deformation) or FRACTURES (brittle deformation)
elastic deformation
rock will return to original size / shape when stress is removed

*earthquakes release elastic energy*
ductile deformation
rock flows after elastic limit surpassed
brittle deformation
rock fractures after elastic limit surpassed
factors influencing how rock strength & thus deformation
1)temperature

2)confining pressure

3) rock type [rheology]

4)availability of fluids

5)time [strain rate]
temperature and confining pressure
affecting rock deformation
low temp & low pressure:
Brittle Deformation
[fractures]

high temp & high pressure:
Ductile Deformation
[flows]
clays
rock type
affecting rock deformation
crystalline rocks composed of minerals = brittle fracture

weakly cemented sedimentary rocks & meta rocks w. zones of weakness = ductile flow
"rock structures"
term
deformations from mountains to fractures

(the largest folds to the smallest fractures)
when studying a region geologists:
identify & describe the dominant rock structure

-aided by aerial photography, satellite imagery, digital topography, global positioning systems (GPS)
used to decribe orientation of rock layer
1)STRIKE (trend)

2)DIP (inclination)

by knowing strike & dip geologists can predict nature, structure & faults of the rock unit
strike
compass direction of the line of intersection of inclined rock layer or fault with horizontal plane

-expressed as angle relative to N (N10*E ->strike is 10* E of N)
dip
angle of inclination of the rock compared to horizontal plane

includes angle of inclination and direction rock is inclined toward
folds
rocks bent into series of wavelike undulations
(during mtn building especially)

-microscopic to hundreds of meters

-result from COMPRESSIONAL stresses
-->the shortening and thickening of crust

PARTS:
limbs
axis
axial plane
limbs

(part of fold)
refers to the two sides of a fold
AXIS
(book calls hinge)

(part of fold)
where fold is divided along max curvature pt
--just a line

(like dividing into symmetrical sides)
Axial Plane

(part of fold)
imaginary surface dividing fold in half
--PLANE dividing into "symmetrical sides" of fold
ANTICLINE

type of fold
upward / arched rock layers

(the limb of an anticline can also be the limb of a syncline)
SYNCLINE

type of fold
downfolds / troughs of rock layers
basic folds can be :
-symmetrical
-asymmetrical
-overturned (type of asymmetrical)
symmetrical folds
limbs are mirror images of eachother
asymmetrical folds
&
overturned folds
asymmetrical folds:
limbs are NOT mirror images

overturned folds:
in asymmetrical folds when one limb is tilted beyond the vertical
(can go so far as to lay on its side ->axis would be horizontal)
Plunging of folds

(and how anticline & sincline plunge)
folds plunge when their axis penetrates the ground

anticlines point IN the direction they're plunging

sinclines point the OPPOSITE direction they're plunging

*plunging = from hitting surface down*
Monocline

(type of fold)
large, step like folds in otherwise horizontal strata

-ONLY ONE INCLINED LIMB (the other horizontal)

-result from movement along buried faults
DOME

(type of fold)
upward displacement of rocks
-circular, elongated structure
**LOOKS LIKE A BALD HEAD**

-OLDEST rocks in CENTER, youngest rocks at edge

-can be formed by magma intrusion
BASIN

(type of fold)
downward displacement of rock
-circular, elongated structure
**LOOKS LIKE A BOWL**

-YOUNGEST rocks in CENTER,
oldest at edges
faults
fractures in rock allowing displacement to occur

-sudden movements along faults cause most earthquakes
dip-slip fault
faults in which movement is parallel to dip (inclination) of fault surface
-can produce fault scarps
-parts = hanging wall & footwall
fault scarp
long low cliffs produced by vertical displacement along dip slip fault
hanging wall
v
footwall
HANGING WALL:
rock surface above fault
(where miners hung their lamps)

FOOTWALL:
rock surface below fault
(miners foot was)
2 Types of Dip-Slip faults
1) Normal Fault

2)Reverse Faults
Normal Fault

[type of dipslip fault]
when hanging wall moves DOWN relative to foot wall
-accomodates extension of crust
-large scale normal faults = associated w/ "fault-block mtns"
Fault Block Moutains
large scale normal faults

-extend for tens of KMs
Horsts
alternating uplifted fault blocks
from movement along fault

-create elevated ranges
Grabens
down dropped blocks from movement along fault

-FORM BASINS

[half grabens = tilted fault blocks]
Reverse & Thrust Faults
hanging wall moves up relative to footwall
-accomodate shortening of crust
-result from COMPRESSIONAL forces

*reverse faults = dips greater than 45*
thrust faults = dips less than 45*
STRIKE SLIP FAULTS

{as opposed to dip slip}
displacement is horizontal and parallel to strike of fault

2 types:
1)RIGHT LATERAL:
as you face the fault the block on the opposite side moves right

2)LEFT LATERAL:
as you face the fault the block on the opposite side moves left
Transform Fault
Types of strike slip fault

-cuts through the lithosphere and accommodates motion between 2 large crustal plates

-many cut thru oceanic lithosphere & link spreading ocean ridges

*EX. SAN ANDRES
SAN ANDRES

example of
major transform fault

(a large strike slip fault cutting thru lithosphere)
hydrologic cycle
-endless cycle
-constantly movement
-powered by energy from the sun (provides link between oceans & continents)
-winds transport moisture filled air
-water falls in ocean = completed cycle
-water falls on land = must make its way back to ocean

*BALANCED*
(ie total water vapor in atmosphere remains the same)
infiltration
the portion of water that soaks into the ground

move downward then laterally (into streams oceans etc)
runoff
the water that flows over the surface into bodies of h2o ... when rate of rainfall greater than land's ability to absorb it
evapotranspiration
combined effect of transpiration & evaporation

[transpiration = water released by plants into atmosphere]
earth's allocation of h2o
oceans: 97 %

glaciers: 2 %

groundwater: .6 %

lakes/rivers, atmosphere: ~.02 %
most important erosional agent?
RUNNING H2O
sheet flow
broad thin sheets of h2o across ground

*depends on infiltration capacity of soil*

runoff begins as sheet flow
infiltration rate
CONTROLLED BY:

1)intensity / duration of rainfall
2)prior wetted condition of soil
3)soil texture
4)slope of land
5)vegetation cover
rills
tiny channels of current developed from sheet flow

*happens after sheet flow*

-carries water to streams
stream's erosional power
depends on velocity!
velocity of stream
depends on :
1)gradient
2)shape / size / roughness of channel
3)discharge
gradiant
slope of the stream

measured by vertical drop of stream over fixed distance

**the steeper the gradiant the more energy available for streamflow**

**higher gradiant = higher velocity**
cross-sectional shape

of stream
affecting velocity
determines amount of water in contact w/channel & thus the amt of frictional drag

*most efficient stream = least perimeter for its cross section

*less water in contact = less frictional drag = higher velocity
size & roughness of channel

affecting velocty of stream
bigger size = lower perimeter:cross section ratio = increases velocity

smooth channel = more uniform flow

irregular channel filled w/ boulders = slows flow
discharge
amt of water flowing past a certain point at a given time

(cross sectional area)x(velocity)

*normally not constant due to rain & snowmelt

*if discharge increases the stream either increases depth & stays at same rate OR must flow faster*
changes from upstream to downstream
1)profile
2)velocity increases
3)discharge increases
4)channel size increases
5)gradiant DECREASES
6)channel roughness DECREASES


(width depth and velocity increase due to more water added to stream from groundwater & other sources)
profile
(aka longitudinal profile)
cross sectional view of a stream from source area (head) to mouth (where river's emptied)
base level
the lowest elevation to which a stream can erode

*where mout enters body of h2o*

--accounts for fact that streams have low gradients near mouths

2 types:
1)ultimate base level
2)local / temporary base level

*raised base level = deposition
*lower base level = erosion
--->lower base level -->excess energy --> downcuts channel to balance
ultimate base level
sea level
temporary / local base level
lakes, resistent layers of rock

limits stream

*when stream enters lake velocity approaches 0 & erosional power is gone

*upstream from resevoir = gradiant reduced, lower velocity, lower transporting ability

*change in local base level = waterfall

*changes river profile
changes from upstream to downstream
1)profile
2)velocity increases
3)discharge increases
4)channel size increases
5)gradiant DECREASES
6)channel roughness DECREASES


(width depth and velocity increase due to more water added to stream from groundwater & other sources)
changes from upstream to downstream
1)profile
2)velocity increases
3)discharge increases
4)channel size increases
5)gradiant DECREASES
6)channel roughness DECREASES


(width depth and velocity increase due to more water added to stream from groundwater & other sources)
profile
(aka longitudinal profile)
cross sectional view of a stream from source area (head) to mouth (where river's emptied)
base level
the lowest elevation to which a stream can erode

*where mout enters body of h2o*

--accounts for fact that streams have low gradients near mouths

2 types:
1)ultimate base level
2)local / temporary base level

*raised base level = deposition
*lower base level = erosion
--->lower base level -->excess energy --> downcuts channel to balance
ultimate base level
sea level
temporary / local base level
lakes, resistent layers of rock

limits stream

*when stream enters lake velocity approaches 0 & erosional power is gone

*upstream from resevoir = gradiant reduced, lower velocity, lower transporting ability

*change in local base level = waterfall

*changes river profile
profile
(aka longitudinal profile)
cross sectional view of a stream from source area (head) to mouth (where river's emptied)
base level
the lowest elevation to which a stream can erode

*where mout enters body of h2o*

--accounts for fact that streams have low gradients near mouths

2 types:
1)ultimate base level
2)local / temporary base level

*raised base level = deposition
*lower base level = erosion
--->lower base level -->excess energy --> downcuts channel to balance
ultimate base level
sea level
temporary / local base level
lakes, resistent layers of rock

limits stream

*when stream enters lake velocity approaches 0 & erosional power is gone

*upstream from resevoir = gradiant reduced, lower velocity, lower transporting ability

*change in local base level = waterfall

*changes river profile
graded stream
correct slope & characteristics to maintain velocity to transport material supplied

[not eroding or depositing, just transporting]

->becomes a self regulating system -->EQUILIBRIUM
load
transported material by stream

1)dissolved load
2)suspended load
3)bed load
dissolved load
supplied by goundwater

*groundwater dissolves minerals and such from soil
suspended load
largest part of a stream's load

sediment suspended in h2o

-controlled by velocity and settling velocity (the speed @which particles settle)-larger the particle = more rapid settling)
bed load
sediment too large to be carried in suspension
-move along bottom of stream

moves by saltation (jump / skip along bed

-in motion intermittantly
capacity
maximum load of solid particles that a stream can transport

-1/2 controlling load stream can carry
competance
max particle size a stream transports
-determined by stream velocity

-2/2 controlling load stream can carry

*competence increases as velocity squared (v increases 2 times, competence increases 4 times)
deposition
caused by decrease in velocity
-competence reduced
-sediment begins to drop out

1)channel deposits
2)floodplain deposits
3)alluvial fans
4)deltas
channel deposits
1)BARS:
-coarser components (sand gravel)
-temporary

2)BRAIDED STREAMS
-stream deposits material on floor
-accumulate thick enough to choke channel
-force stream to split in multiple paths
--converging & diverging channels threading along bars
*often when load supplied exceepds competency / capacity
*also form when abrupt decrease in gradient or decrease in discharge

3)DELTAS
-forms when stream enters body of h2o
-dying current deposits load of sediments
-delta grows outward -> streams gradient lessens
--channel becomes choked w.sediment & river seeks higher gradient, shorter route
--main channel divides into several smaller ones (distributaries)
floodplain deposits
[part of valley that gets flooded]

1)NATURAL LEVEES
-form parallel to stream channel by successive floods over many yrs
-when stream overflows it flows over land as broad sheet---decreasing velocity & allowing for load to be deposited
Alluvial Fans
develop where high gradiant stream leaves a narrow valley
-drop in v causes dumpage of load quickly in cone / fan shaped accumulation

-slopes outward in broad arc


**deposited on land
[deltas deposited in water]
3 types of delta beds
1)FORESET BEDS
-coarser particles drop out immediately form layers sloping down

2)TOPSET BEDS
-usually covers foreset bed
-deposited during flood stage

3)BOTTOMSET BEDS
-finer silts and clays settling out at a distance from mouth
-horizontal layers
stream valleys
most common landform on earth

2 types:
1)NARROW VALLEYS
-v shaped
-downcutting toward base level
-can include rapids & waterfalls

2)WIDE VALLEYS
-often include floodplains & meanders
floodplains
in wide valleys
1)erosional floodplains

2)depositional floodplains
meanders
in wide valleys
streams that move in sweeping bends

-can produce CUT BANKS
(the zone of erosion outside of a meander)

-when the neck of a meander is narrowed close enough the river can erode thru the narrow neck to the next loop
-->creates new shorter segment [CUTOFF]
---abondoned bend of river = OXBOW LAKE

-can create a point bar
point bar

(resulting from a meander)
crescent shaped accumulation of sediment deposited inside of meander
oxbow lake

(resulting from a meander)
the abandoned bend when river assumes the shorter route, cutting off the neck and creating a "cutoff" (the new shorter segment)
incised meander
meanders in steep, narrow valleys

-caused by drop in base level or uplift of a region

(probably originally developed on floodplain that was near base level -- a change in base level cause downcutting
terraces
-remnants of former floodplain
-after a river has adjusted to drop in base level by downcutting
floods
most common & most destructive geologic hazard

caused by natural and anthropogenic factors
flood control
-artificial levees
-flood control dams
-channelization
rivers meander more in:
SOFT SEDIMENT
How long does it take to remove groundwater resources:
TENS of years

(turnover of groundwater is not in our lifetime)
are glaciers shrinking?
YES bc of global warming

which appears anthropogenic
rivers change on what time scale?

river turnover time scale?
rivers change in time scale of our lifetime

river turnover takes place in a few weeks
problems with flood control?
by trying to control floods the frequency is lowered but intensity is increased when one finally does occur
what % of earth's freshwater is groundwater?
0.6 %
measure of amt of water that can be stored by rock / sediment
porosity
currently glaciers cover __% of earth's land area
10 %
during last major ice age advance sea level:
was 100 m lower
broad deposit of stratified drift thats deposited beyond the end moraine of an ice sheet is:
Outwash Plane
what fault displaces older strata over younger strata?
THRUST FAULTS
gentle rainfall favors

(infiltration or runoff?)
infiltration
surface lacking vegetation favors?

(infiltration or runoff??)
runoff
what caused the formation of yosemite and the great lakes?
GLACIERS