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120 Cards in this Set

  • Front
  • Back
base level
the level below which a stream cannot erode.
capacity vs. competence
capacity: the total amount of sediment a stream is able to transport.
competence: a measure of the largest particle a stream can transport; a factor dependent on velocity.
drainage basin
the land area that contributes water to a stream.
headward erosion
the extension upslope of the head of a valley due to erosion.
the movement of surface water into rock or soil through cracks and pore spaces.
laminar flow vs. turbulent flow
laminar flow: the movement of water particles in straight-line paths that are parallel to the channel. the water particles move downstream without mixing.
turbulent flow: the movement of water in an erratic fashion often characterized by swirling, whirlpool-like eddies. most streamflow is of this type.
tiny channels that develop as unconfined flow begins producing threads of current.
transportation of sediment through a series of leaps or bounces.
sheet flow
runoff moving in unconfined thin sheets.
stream head
the source area of a stream.
stream mouth
the point downstream where the river empties into another water body.
hydrologic cycle
the unending circulation of earth's water supply. the cycle is powered by energy from the sun and is characterized by continuous exchanges of water among the oceans, the atmosphere, and the continents.
distribution of water on the earth
water content of earth's hydrosphere =about 1.36 billion cubic kilometers. 97.2%= oceans
2.15%= ice sheets and glaciers
0.65%= lakes, streams, subsurface water, and the atmosphere.
Changes along stream profile
gradient, velocity, discharge, and channel size
the slope of a stream, generally expressed as the vertical drop over a fixed distance. the higher the gradient is, the greater the velocity.
the quantity of water in a stream that passes a given point in a period of time. when discharge increases, the channel size must increase or the water must flow faster.
base level
the level below which a stream cannot erode (the level at which the mouth of a stream enters the ocean, a lake, or another stream. sea level is referred to as "ultimate base level".
impacts of changing base levels
when a dam is built along a stream course, the reservoir that forms behind it RAISES the base level of the stream; the gradient, velocity, and sediment-transporting ability are reduced. this causes the stream to deposit material and build up its channel.
if the base level is LOWERED, either by uplifting of the land or by a drop in sea level, the stream would have excess energy and would downcut its channel to establish a balance with its new base level (erosion).
types of loads
dissolved load, suspended load, and bed load
dissolved load
when a stream transports its load in solution
suspended load
when a stream transports its load in suspension (fine sediment carried within the body of flowing water). usually only clay-size or fine particles are can be carried this way, but during flood stage, larger particles are carried as well.
bed load
when a stream transports its load along the bottom of the channel. the load consists gennerally of larger, coarser particles that are too large to be carried in suspension. the particles move along the bottom by rolling, sliding, and saltation (leaping).
a general term for all stream-deposited sediment.
channel deposits
commonly refered to as bars; sand and gravel deposits in a stream channel. these are only temporary because the material will be picked up again by the running water and will be transported farther downstream. point bars are crescent-shaped accumulations of sand and gravel.
floodplain deposits
a floodplain is the flat, low-lying portion of a stream valley subject to periodic flooding. the deposits (or alluvium!) consists of coarse sands and gravels that were originally deposited as point bars by meanders shifting laterally across the valley floor. there are also fine sands, silts, and clays that were spread across the floodplain whenever water overflowed the channel during flood stage.
alluvial fan
a fan-shaped deposit of sediment formed when a stream's slope is abrubtly reduced.
an accumulation of sediment formed where a stream enters a lake or an ocean.
narrow vs. wide valleys
narrow: broader at the top, downward erosion; features can include rapids and waterfalls.
wide: stream's energy is directed from side to side; floodplain is produced.
a looplike bend in the course of a stream. an incised meander is a meandering channel that flows in a steep, narrow valley; they form either when an area is uplifted or when base level drops.
cut bank
the area of active erosion on the outside of a meander.
a short channel segment created when a river erodes through the narrow neck of land between meanders.
oxbow lake
a curved lake produced when a stream cuts off a meander.
a flat, benchlike structure produced by a stream, which was left elevated as the stream cut downward.
types of drainage patterns
dendritic, radial, rectangular, and trellis
dendritic pattern
a stream system that resembles the pattern of a branching tree. it forms where underlying bedrock is relatively uniform, such as flat-lying sedimentary strata or massive igneous rocks.
radial pattern
a system of streams running in all directions away from a central elevated structure, such as a volcano. it typically develops on isolated volcanic cones and domal uplifts.
rectangular pattern
a drainage pattern characterized by numerous right angle bends that develops on jointed or fractured bedrock. it develops where the bedrock is crisscrossed by a series of joints and faults.
trellis pattern
a system of streams in which nearly parallel tributaries occupy valleys cut in folded strata. it forms in areas underlain by alternating bands of resistant and less resistant rock and is particularly well displayed in the folded appalachian mountains.
ways that streams increase length
1. by building a delta at its mouth.
2. headward erosion (extending the head of its valley upslope).
types of floods
floods: the most common and most destructive of all geologic hazards.
types: regional, flash, ice-jam, dam-failure
regional floods
some are seasonal (i.e. rapid melting of snow or heavy spring rains).
some are caused by extended wet periods
ice-jam floods
frozen rivers are susceptible to this type of flooding. as the level of a stream rises, it breaks up the ice and creates ice flows that can pile up on channel obstructions- such an ice jam creates a dam across the channel. when the dam fails, the water stored behind the dam is released and causes a flash flood downstream.
dam-failure floods
dams are built for flood protection; if a larger flood occurs, the dam is overtopped.
factors that determine water velocity
gradient, discharge
rock or sediment through which groundwater moves easily.
(confining layer) an impermeable bed that hinders or prevents groundwater movement (aqua=water, tard=slow). clay is a good example.
capillary fringe
a relatively narrow zone at the base of the zone of aeration. here water rises from the water table in tiny threadlike openings between grains of soil or sediment.
gaining stream vs. losing stream
gaining stream: streams that gain water from the inflow of groundwater through the streambed.
losing stream: streams that lose water to the groundwater system by outflow through the streambed.
a type of topography formed on soluble rock (especially limestone) primarily by dissolution. it is characterized by sinkholes, caves, and underground drainage.
porosity vs. permeability
porosity: the volume of open spaces in rock or soil.
permeability: a measure of a material's ability to transmit water.
a form of limestone that is deposited by hot springs or as a cave deposit.
a collective term for the dripstone features found in caverns.
the icicle-like structure that hangs from the ceiling of a cavern.
the columnlike form that grows upward from the floor of a cavern.
a depression produced in a region where soluble rock has been removed by groundwater.
water table
the upper level of the saturated zone of groundwater.
zone of aeration
the area above the water table where openings in soil, sediment, and rock are not saturated but filled mainly with air.
zone of saturation
the zone where all open spaces in sediment and rock are completely filled with water.
why groundwater is important
groundwater represents the largest reservoir of fresh water that is readily available to humans.
it is also important as an erosional agent and also an equalizer of streamflow (i.e. water in a river during a dry period represents rain that fell at an earlier time and was stored underground).
how the level of the water table can vary naturally and by humans
naturally: the addition of water to the groundwater system is closely related to the quantity, distribution, and timing of precipitation. also, groundwater moves slowly and it tends to "pile up" beneath high areas between stream valleys. others causes for the uneven water table are variations in rainfall and permiability from place to place.
humans can also alter the level by pumping water through wells.
why springs flow
1. gaining streams
2. losing streams
3. combination (streams gains in some sections and loses in others)
formation of hot springs and geysers
hot spring: a spring in which the water is 6-9 degrees celcius warmer than the mean annual air temperature of its locality. the source of heat for most hot springs is cooling igneous rock. some are also heated by groundwater circulating at great depths, which heats the water.
geyser: a foundation of hot water ejected periodically from the ground with great force. geysers occur where extensive underground chambers exist within hot igeneous rocks. as cool groundwater enters the chambers, it is heated by the surrounding rock. the water at the bottom is under great pressure; some of the water deep within the chamber quickly turns to steam and the geyser erupts.
artesian wells
a well in which the water rises above the level where it was initially encountered.
nonflowing artesian well: where the pressure surface is below ground level.
flowing artesian well: when the pressure surface is above the ground and a well is drilled into the aquifer.
problems with pumping groundwater and its implications
1. treating groundwater as a nonrenewable source
2. subsidence (sinking of the ground when water is pumped from wells faster than natural recharge processes can replace it).
3. saltwater contamination
creation of caves
most are created at or just below the water table in the zone of saturation. here acidic groundwater follows lines of weakness in the rock, and as time passes, the dissolving process slowly creates cavities and gradually enlarges them into caverns.
beach drift
the transport of sediment in a zigzag pattern along a beach, caused by the uprush of water from obliquely breaking waves.
ebb current
the movement of tidal current away from the shore.
flood current
the tidal current associated with the increase in the height of the tide.
longshore current
a nearshore current that flows parallel to the shore.
shoreline erosional and depositional features
erosional: wave-cut cliffs (cutting of the surf against the base of coastal land); sea arches (when two caves on opposite sides of a headland unite); when the arch falls in, it leaves a sea stack.
depositional: spits (an elongated ridge of sand that projects from the land into th emouth of an adjacent bay); tombolo (a ridge of sand that connects an island to the mainland or to another island).
spring and neap tides
spring tide: the highest tidal range. occurs near the times of the new and full moons.
neap tide: the lowest tidal range, occuring near the times of the first and third quarters of the moon.
wave refraction
a change in direction of waves as they enter shallow water. the portion of the wave in shallow water is slowed, which causes the waves to bend and align with the underwater contours.
parts and measurements of waves
crest- top of wave
trough- bottom curve
height- vertical distance between trough and crest
wavelength- distance between successive crests (or troughs).
factors that determine wave features (height, length, period)
1. wind speed
2. the length of time the wind has blown
3. the fetch, or distance that the wind has traveled across open water.
impact of wave refraction
wave refraction affects the distribution of energy along the shore and thus strongly influences where and to what degree erosion, sediment transport, and deposition will take place.
human response to coastal erosion
atlantic and gulf coasts: wide beaches, problems from storms when a barrier is developed for homes or as a resort.
pacific coast: narrow beaches, steep cliffs, problem of narrowing beaches
causes of tides
the moon's gravitational force can cause the water to bulge on the side of the earth nearest the moon. an equally large tidal bulge is produced on the side of the earth opposite the moon. both are caused by the pull of gravity.
a type of movement common to mass-wasting processes that refers to the freefalling of detached individual pieces of any size.
a type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid.
a movement common to mass-wasting processes in which the material moving downslope remains fairly coherent and moves along a well-defined surface (landslide).
factors that may increase the odds of having a mass wasting event
increased slope, removal of vegetation (plants protect against erosion), earthquakes
classification of mass wasting events by velocity
most rapid type is called rock avalanche, but most do not move this quickly.
classification of mass wasting events by type of material
depends on whether the descending mass began as unconsolidated material or bedrock (terms like debris, mud, earth, or rock)
classification of mass wasting events by type of motion
fall, slide, or flow
alluvial fnas
a fan-shaped deposit of sediment formed when a stream's slope is abruptly reduced.
an apron of sediment along a mountain front created by the coalescence of alluvial fans.
desert pavement
a layer of coarse pebbles and gravel created when wind removed the finer material.
a hill or ridge of wind-deposited sand.
deposits of windblown silt, lacking visible layers, generally buff-colored, and capable of maintaining a nearly vertical cliff.
perennial stream vs. ephemeral stream
perennial: a lasting stream
ephemeral stream: a stream that is usually dry because it carries water only in a response to specific episodes of rainfall.
the flat central area of an undrained desert basin.
playa lakes
a temporary lake in a playa.
a cobble or pebble polished and shaped by the sandblasting effect of wind.
a streamlined, wind-sculpted ridge having the appearance of an inversted ship's hull that is oriented parallel to the prevailing wind.
two types of deserts based on the amount of precipitation
1. desert
2. steppe (a more humid variant of the desert)
role of surface water in deserts
deserts have ephemeral streams. unlike in humid regions, these streams lack an extensive system of tribuataries.
running water, although infrequent, does most of the erosional work in deserts.
mechanisms of wind erosion
1. deflation (the lifting and removal of loose material).
2. abrasion (windblown sand cuts and polishes exposed rock surfaces).
factors that determine shape of dunes
wind direction and velocity, availability of sand, and the amount of vegetation present.
wastage of a glacier that occurs when large pieces of ice break into the water.
a deep crack in the brittle surface of a glacier.
granular recrystallized snow. a transitional stage between snow and glacial ice.
a period of rapid glacial advance. surges are typically sporadic and short-lived.
a large floating mass of ice, detached from a glacier and carried out to sea.
type of glaciers resulting from continental and mountainous glaciation
1. valley glaciers, or alpine glaciers (a glacier confined to a mountain valley, which in most instances had previously been a stream valley).
2. ice sheets (a very large, thick mass of glacial ice flowing outward in all directions from one or more accumulation centers).
3. outlet glaciers (a tongue of ice normally flowing rapidly outward from an ice cap or ice sheet, usually through mountainous terrain to the sea).
4. piedmont glaciers (a glacier that forms when one or more alpine glaciers emerge from the confining walls of mountain valleys and spread out to create a broad sheet in the lowlands at the base of the mountains).
types of glacial movement
1. plastic flow (a type of glacial movement that occurs within the glacier, below a depth of approximately 50 meters, in which the ice is not fractured).
2. basal slip (a mechanism of glacial movement in which the ice mass slides over the surface below).
zone of fracture
the upper portion of a glacier consisting of brittle ice.
zones in glacial budget
glacial budget: the balance, or lack of balance, between accumulation at the upper end of the glacier and loss at the lower end.
1. zone of accumulation (the part of a glacier characterized by snow accumulation and ice formation. the outer limit of this zone is the snowline.
2. zone of wastage (the part of a glacier beyond the snowline where annually there is a net loss of ice).
mechanisms of glacial erosion
1. plucking (the process by which pieces of bedrock are lifted out of place by a glacier).
2. abrasion (the grinding and scraping of a rock surface by the friction and impact of rock particles carried by water, wind, and ice).
results of glacial abrasion
rock flour is produced; glacial striations
names and formation of the landforms resulting from glacial erosion or deposition
1. glaciated valleys
2. aretes (sharp-edged ridges) and horns (sharp pyramid-like peaks)
3. roche moutonnee (an asymmetrical knob of bedrock)
the gaseous protion of a planet, the planet's envelope of air.
atmospheric science
the study of the atmosphere, its processes, the effects other systems have on the atmosphere, and the effects of the atmosphere on these other systems.
the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences.
the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.
Ferrel cell
usually shown between the Hadley and Polar cells. the main 'problem' with the Ferrel cell is that it is thermally indirect.
Hadley cell
a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator. This circulation is intimately related to the trade winds, tropical rainbelts, subtropical deserts and the jet streams.
Milankovitch cycles
the collective effect of changes in the Earth's movements upon its climate
an important parameter of the orbit that defines its absolute shape. Eccentricity may be interpreted as a measure of how much this shape deviates from a circle.
(axial tilt); the inclination angle of a planet's rotational axis in relation to a perpendicular to its orbital plane.
a change in the direction of the axis of a rotating object.