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geol 102 midterm
Terms in this set (106)
the process by which river lengthen their channels
defined as the volume of water passing through a cross-section of the river at a given time (volume of water / time)
Main water reservoirs
Why is water a polar molecule?
-water has positive hydrogen atoms and negatively charged oxygen atoms
-Creates hydrogen bonds
-So water "sticks" to itself
-which makes it a "universal solvent"
-water expands as it freezes
-water has high surface tension
-water has capillary action
-water has a high heat capacity (it requires a lot of energy to change its temperature)
-water is a powerful solvent
average time that a water molecule spends in a particular reservoir during the hydrologic cycle
water residence time rank
Rank from 1 to 5 (1= shortest, 5=longest)
the entire area drained by a given river
the ridge that separates two drainages
the ridge that separates watersheds of rivers that flow to different oceans
Different drainage networks
Dendritic - homogenous bedrock
Rectangular - joint
Radial - Mountain
Parallel - sloping surfaces
How would you describe the Great Basin?
A gigantic area of interior drainage
volume of water passing through the channel in a given amount of time
coarser sediment travels along the bottom
How does bed load move?
rolling, sliding, saltation
fine sediment carried in suspension
material (ions) transported in solution
Transport of sediment
During saltation, clasts bounce along the bed and knock other clasts into the flow.
Streams transport sediment in many forms: dissolved ions are in solution, tiny suspended grains are distributed through the water, and the bed load slides, rolls, and/or undergoes solution. Sediment is transported as dissolved, suspended, and bed load
the movement of hard particles such as sand over an uneven surface in a turbulent flow of air or water
how does water velocity and thus a carrying capacity and competency vary across a meander bend?
How does water-transported sediment (alluvium) change downstream from its source?
what happens to a river gradient and discharge downriver from its source?
Why is river discharge important?
greatest size of sediment a stream can carry
total amount of sediment a stream can carry
why are competence and capacity important?
-it is important measures of a stream's ability to carry sediment
-competency and capacity increase exponentially as velocity increases
-They decrease exponentially as velocity decreases!
-As water velocity decreases, it deposits material.
-As water velocity increases, it transports material and erodes its channel.
A fan-shaped deposit of alluvium
-Alluvium= water-transported material
the term used to describe coalescing alluvial fans.
-defined by multiple channels that form a braided pattern
-tend to form where there are rapid fluctuations in discharge and in coarse alluvium.
-characterize mountainous and near-source areas
they wind across their floodplains
-the area gets covered by water during floods.
the flat area around a river that is covered with sediment as a result of frequent flooding
-during flooding, the area gets flooded
Erosion at waterfalls
-greatest erosional energy occurs where the water hits the plunge pool
-2nd greatest amount of erosional energy occurs where the water spills over the top.
-undercutting at base and channel down-cutting at top
When and why do rivers flood?
What causes a river to flood?
River - Besides their damage, how are they beneficial?
How have floods changed as the landscape has become more urbanized?
its made flooding more severe by increasing river discharges soon after a rainstorm
Flood control measures
What are the long-term effects on the mississippi, especially on its delta and its relation to the Atchafalaya?
rocks or deposits that can hold and allow passage of groundwater - require high porosity AND permeability
rocks or deposits that prevent the passage of groundwater - require low permeability
below the land surface that is saturated with water
water seeps from the ground surface directly above the aquifer
streams that flow all year
How does permanent streams relate to groundwater?
is a landscape formed primarily by dissolution of bedrock by groundwater
most igneous and metamorphic rocks make poor aquifers - why?
because they are made of interlocking crystals, they typically have very low permeability
which of the following ways of estimating flood frequencies is the most accurate?
Theyre the same accuracy - Annual probability and Recurrence Interval
percentage of quartz grains in sedimentary deposits increase downriver. Why?
Quartz is less susceptible to chemical weathering than other minerals
During flooding, a river's discharged increases significantly. If the cross-sectional area of the channel were to stay the same, what would happen to the velocity of the current?
Which of the following types of mass movements takes place along a curved failure surface and shows rotational downslope movement?
In much of the Grand Canyon, the Colorado River flows roughly east-west, while the sedimentary rocks are tilted gently southward. Where would you expect to see more evidence of sliding?
North of the river
wind is not primarily responsible for which of the following?
Accumulation and rounding of boulders at the base of a cliff.
Mechanical weathering does which of the following?
changes the size and shape of rocks
joints are important for chemical weathering because
they permit greater infiltration of water
karst landscapes typically develop from which weathering process?
if you are walking or crawling through a cave, you are experiencing a place that
partially formed when it was below the water table but is now above the water table
sinkholes typically form in what type of rick?
What is the difference between permeability and porosity?
Permeability is a measure of how easily fluids move through a rock or sediment; porosity is a measure of how much fluid the rock or sediment can hold.
What is most necessary for a sediment or rock to be a good aquifer?
high permeability and porosity
what best represents hydraulic head?
the elevation to which groundwater will rise without pumping
the 1976 Big thompson river flood
was a flash flood in colorado brought on by unusually heavy rains in a small area
A flood that is estimated to have a 5% annual probability
has a 20 year recurrence interval
Failure of artificial levees during floods frequently involves undermining, which
happens because the rising water levels exert high pressures that force water through the bottom of the levee
Local base levels are important because
the impose a lower limit to the elevation of the stream above it
lakes are frequent features found along rivers. Which of the following statements about lakes is true?
they mark local base levels
Typically contain a higher percentage of coarse material and show a greater fluctuation in discharge than meandering rivers
rivers transport sediment by which of the following mechanisms?
-as small particles in suspension within the water
-as dissolved sediment
-as sediment that bounces and rolls along the bottom of the channel
What is meant by "relief" when referring to topography?
the vertical distance (elevation difference) between two places
which of the following lists shows water sources arranged in order of decreasing abundance?
ice and snow, freshwater lakes, swaps, ricers and streams
what is meant by "residence time" when referring to water and the hydrologic cycle?
the average length of time a water molecule remains in a given reservoir
steep slopes are more prone to mass wasting than gentle slopes because
the steeper the slope, the greater the ratio of the downward pull of gravity to the resistance force
which material, when dry, tends to form the greatest angle of repose?
which of the following are some indications of past mass movements?
both tilted tress and hummocky topography
Which of the following lists shows mass wasting processes in order of increasing speed of movement?
creep, slump, slide, fall
in a slump or landslide, the headscarp is
the steep area immediately above and behind the slide.
are volcanic mud- and debris flows
which of the following statements about rock weathering is true?
-physical weathering aids chemical weathering by exposing more surface area
-weathering is the in-place breakdown of rock
-water is necessary for chemical weathering
-chemical weathering aids physical weathering by weakening the rock
Hydrolysis is a type of chemical weathering that
tends to turn feldspar minerals into clay
which of the following statements is true about chemical weathering?
chemical weathering is more effective in fine-grained material than coarse-grained material because fine-grained material has more overall surface area than coarse material
An angular unconformity is
the gap in the rock record we can infer where younger sedimentary or volcanic rock overlies older sedimentary rock that is inclined at a different angle
the principle of superposition states that
in sedimentary rocks, the youngest rock is on the top
two isotopes of the same element are characterized by
having the same number of protons but different number of neutrons
the material in a schist can turn into an intrusive igneous rock by
melting because of high temperature and then cooling
subduction zones form at what type of plate margin
When does erosion take place?
erosion takes place when velocity increases
How does erosion occur?
by scouring and abrasion, breakage, and dissolution, typically during high discharges (=flooding)
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