116 terms

Geology Exam- Unit 2

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Weathering
the breakdown of rocks at the surface of the earth
Erosion
the movement of sediment over the surface of the land, carried by flowing water, wind, ice, or gravity
Chemical weathering
breaks down rocks and forms unstable materials; dissolution, oxidation, hydrolysis
dissolution
ionic bonds neutralize by water molecules
oxidation
any reaction where electrons are lost from one element
hydrolysis
the reaction of any substance with water
mechanical weathering
physical breaking of rocks into smaller pieces; frost wedging, salt crystal growth, sheeting, thermal expansion, Biological activity
soil
combination of mineral and organic matter, water, and air
detrial rocks
contains transported sediments as solid particles
Chemical Rocks
sediement composed of minerals that were once in a solution
recrystalization
development of more stable minerals from less stable ones
Lithification
sediments transformed into solid rock by compaction and cementation
Detrial Sedimentary rocks
Quartz, feldspar, micas, clay minerals
Shale/ Mudstone
most common sedimentary rock; used as barriers because of the inability to be penetrated
Coarse Detrial Rocks
conglomerate, Breccia
Limestone
most common chemcical sedimentary rock;
Coal
organic sedimentary rock;
Coarse grain
over 2 mm
Medium grain
1/16 to 2 mm
Fine grain
1/16 to 1/256 mm
Very Fine grain
less than 1/256
Diagnetic Sedimentary Rocks
Chert, dolostone
Mass wasting
refers to the downslope movement of rock, regolith, and soil under the direct influence of gravity
What mass wasting is classified by
type of material, type of motion, velocity
types of mass wasting
slump, rockslide, debris flow, earthflow
Controls and triggers of mass wasting
water, slope angle
slump
movement of a mass of rock or unconsolidated material as a unit along a curved surface
rockslides
slabs of bedrock slide down a slope
earthflow
the downslope movement of water-saturated, clay-rich sediments. Characterisitc of humid regions
factors that determine velocity
gradient (slope), channel (size, shape, roughness), Discharge (volume of water per a point per unit time)
alluvian fan
a delta-form deposit out the mouth of intermitten streams
diagenesis
term for all of the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification
lithification
process by which unconsolidated sediments accumulates are transformed into solid sedimentary rocks
compaction
a type of lithification in which the weight overlying material compresses more deeply buired sediment.
cementation
as material precipitates from water that percolates through the sediment, open spaces are filled and particles are joined into a mass solid
clastic texture
rocks that display discrete fragments and particles that are semeneted and compacted together
nonclastic
minerals form a pattern of interlocking crystals
lahars
debris flow composed mostly of volcanic materials on the flanks of volcanoes
creep
a type of mass wastin that involves the gradual downhill movement of soil and regolith
sheet flow
when runoff initinally flows in broad thin sheet across hillslopes
river
streams that carry substantial amounts of water and have numerous tributaries
flow velocity
channel slope or gradien; channel size and cross-sectional shape; channel roughness; the amount of water flowing in a channel
gradient
the slope of a stream channel, expressed as the vertical drop of a stream over a specified distance
cut bank
zone of active erosion
deltas
where sediment-charged streams meet the final destination of standing water
debris flow
a flow of soil and regolith containing a large amount of water. Most common in semiarid mountainous regions and on the slopes of some volcanoes.
natural levee
an elevated landform composed of alluvium that parallels some streams and acs to confine their water, except during flood stage
groundwater
-mildy acidic and dissolves soluble rock
-contains weak carbonic acid
-underground equivalent of streamflow
zone or aeration
area above the water table
zone of soil moisture
water held by molecular attraction on soil particles in the near-surface zone
Capillary fringe
extends upward from the water-table; water held between grains by surface tension
water table
the upper limit of the zone of saturation
zone of saturation
zone where water fill most pores in soil or rock
spring
occur where the water table intersects earth's surface
aquifer
permeable rock strata or sediment that transmits groundwater freely
aquitard
an impermeable layer that hinders or prevents water movement
porosity
percentage of total volume of rock and sediment that consists of pore space
permability
the ability of a material to transmit fluid
hydraulic gradient
water-table slope; determined by dividing the vertical difference between the recharge and discharge points by length of flow between these points
hydraulic head
the pressure difference between recharge and discharge points
artesian well
a place where groundwater under pressure rises above the level of the aquifer
problems with groundwater
-groundwater depletion
-subsidence (land falls in)
-saltwater contamination
-sewage
caves
develop when weakly acidic groundwater dissolves limestone
piezometer
a small well used to measure the hydraulic head
cone of depression
develops around the well if the groundwater is extracted faster than it can be replaced
Artesian wells
tap confined, tilted aquifers that are pressurized by upland recharge
springs
locations of natural groundwater discharge that have been important resources, where the water table reaches the surface and releases water
seep
develops where a perched water table intersects the surface
oasis
develop ( in the desert) from spring flow discharge at the end of a long groundwater flow path
over-pumping groundwater problems
depletion, reversing flow direction, saline intrusion, land subsidence, quality issues
Bioremediation
a waste management technique that utilizes bacteria/organisms to remove or neutralize pollutants from a contaminated site, naturally occurring organisms to break down hazardous substances into less toxic/non-toxic substances
sinkholes
when underground cavaties grow so large that there is not enough rock to support the ground above them
natural bridges
remnants of a cave passage
Karst Towers
portion of the earth that remains after the rock around them has been dissolved,usually formed in tropical regions due to heavy rainfall due to heavy rainfall and humidity
dendritic drainage
drainage forms a pattern like a branching tree
radial drainage
drainage develops from a point uplift ( volcanoes and mountainous runoff)
rectangular drainage
drainage flows along orthogonal ( 90 degree or straight lines) jointing in the underlying bedrock
Trellis drainage
drainage develops in deformed strata with alternating *resistant ridges and weak rocks
basin
land area that drains into a specific trunk system ( catchment or watershed)
Divide
separates adjacent drainage basins- a raindrop flows to one basin or the other
ephemeral streams
streams do not flow all year. common in low elevation and low precipitation areas with low water tables ( Death Valley)
permanent streams
defined by water flowing all year. Common where there is abundant rainfall and high water tables
River Discharge
amount/velocity of water flowing in a channel ( volume of water passing a point per unit of time), varies seasonally ( with increased runoff, springtime, hurricanes, etc)
potholes
formed by the sand and gravel swirled by turbulent eddies drilling holes into the bedrock
bed load
comprised of the larger particles that roll, slide, and bounce along the bed of the channel
saltation
pebbles; small materials bouncing between bed load and suspended load that bounces along the bottom/riverbed
suspended load
is made of find particles ( silt and clay) entrained in the flow ( last thing to settle out)
Dissolved load
consists of ions from mineral weathering
competence
maximum grain size transported; decreases with velocity ( larger-mountains_)
capacity
maximum load (course, fine, and dissolved material transported by stream flow
boulders
first sediment to fall out is sediment deposition
Traction, saltation, suspension, and solution
the four methods of transport of material along a river
base level
lowest point to which a stream can erode, the elevation at the mouth that controls erosion along the entire stream ( ultimately, seal level but can also be lake/ledge/resistant rock locally)
valleys
gently sloping stream troughs with sidewalls that define a V shape
alluvium
rise int eh base level or a decrease in discharge causes __
rapids
consist of turbulent water; forms when a rock is resistant to weathering/erosion with a rough surface from flow over large clasts
alluvial fans
conical, fan shaped structures that build at the base of a mountain front. sediments drop out rapidly with a change in stream gradient
meander streams
streams which, over time, become more sinuous- the highest velocity water erodes the outside of a bend ( cut bank)
Point Bar
the inside of the bend in a meandering stream which accreates sediment over time
natural levees
sand rides that parallel the channel
surface zone
ecologically sensitive area that acts as a biofilter; essential to reduce runoff, erosion, and steam energy
avulsion
the main channel feeding a delta may jump to a new location to establish a steeper, shorter path to the basin
abandoned delta lobes
due to avulsion, starved of sediment, slowly compact, dewater, subside, and eventually submerge ex. NOLA
Monsoons
long heavy seasonal rainfall that often causes flooding ( Indian subcontinent)
Flash floods
occur from unusually intense rainfall, hurricane, dam collapes, or levee falure
100 year flood
1% chance every year of a this level of flooding
thalweg
deepest and fastest velocity, upper part
channelization
artificial concrete river beds for controlling the direction of the river, increases velocity of discharge and flood intensity
Strike-slip fault
a fault on which the slip direction is parallel to a strike line( a horizontal line to the fault surface), horizontal movement
Dip-slip fault
movement parallel to the dip line ( a line parallel to the slope of the fault surface), up and down movement
Oblique-slip faults
sliding occurs diagonally on the fault plane; combines dip-slip nad strike-slip displacement; on block moves diagonally relative to another
hanging wall
the rock surface directly above the fault plane
footwall
the rock surface directly below the fault plane
fault scarp
a small step on the ground surface where one side of a fault has moved vertically with respect to the other
normal faults
a fault in which the hanging-wall block moves down the slope of the fault, prevalent at sea-floor spreading centers and continental rift basins
reverse faults
a steeply dipping fault on which the hanging wall block slides up, prevalent at subduction zones and cont-cont collision
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