Geology Exam 3

Front 1

base level

Back 1

the level below which a stream cannot erode.

Front 2

capacity vs. competence

Back 2

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.

Front 3

drainage basin

Back 3

the land area that contributes water to a stream.

Front 4

headward erosion

Back 4

the extension upslope of the head of a valley due to erosion.

Front 5

infiltration

Back 5

the movement of surface water into rock or soil through cracks and pore spaces.

Front 6

laminar flow vs. turbulent flow

Back 6

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.

Front 7

rills

Back 7

tiny channels that develop as unconfined flow begins producing threads of current.

Front 8

saltation

Back 8

transportation of sediment through a series of leaps or bounces.

Front 9

sheet flow

Back 9

runoff moving in unconfined thin sheets.

Front 10

stream head

Back 10

the source area of a stream.

Front 11

stream mouth

Back 11

the point downstream where the river empties into another water body.

Front 12

hydrologic cycle

Back 12

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.

Front 13

distribution of water on the earth

Back 13

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.

Front 14

Changes along stream profile

Back 14

gradient, velocity, discharge, and channel size

Front 15

gradient

Back 15

the slope of a stream, generally expressed as the vertical drop over a fixed distance. the higher the gradient is, the greater the velocity.

Front 16

discharge

Back 16

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.

Front 17

base level

Back 17

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".

Front 18

impacts of changing base levels

Back 18

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).

Front 19

types of loads

Back 19

dissolved load, suspended load, and bed load

Front 20

dissolved load

Back 20

when a stream transports its load in solution

Front 21

suspended load

Back 21

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.

Front 22

bed load

Back 22

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).

Front 23

alluvium

Back 23

a general term for all stream-deposited sediment.

Front 24

channel deposits

Back 24

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.

Front 25

floodplain deposits

Back 25

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.

Front 26

alluvial fan

Back 26

a fan-shaped deposit of sediment formed when a stream's slope is abrubtly reduced.

Front 27

delta

Back 27

an accumulation of sediment formed where a stream enters a lake or an ocean.

Front 28

narrow vs. wide valleys

Back 28

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.

Front 29

meander

Back 29

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.

Front 30

cut bank

Back 30

the area of active erosion on the outside of a meander.

Front 31

cutoff

Back 31

a short channel segment created when a river erodes through the narrow neck of land between meanders.

Front 32

oxbow lake

Back 32

a curved lake produced when a stream cuts off a meander.

Front 33

terrace

Back 33

a flat, benchlike structure produced by a stream, which was left elevated as the stream cut downward.

Front 34

types of drainage patterns

Back 34

dendritic, radial, rectangular, and trellis

Front 35

dendritic pattern

Back 35

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.

Front 36

radial pattern

Back 36

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.

Front 37

rectangular pattern

Back 37

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.

Front 38

trellis pattern

Back 38

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.

Front 39

ways that streams increase length

Back 39

1. by building a delta at its mouth.
2. headward erosion (extending the head of its valley upslope).

Front 40

types of floods

Back 40

floods: the most common and most destructive of all geologic hazards.
types: regional, flash, ice-jam, dam-failure

Front 41

regional floods

Back 41

some are seasonal (i.e. rapid melting of snow or heavy spring rains).
some are caused by extended wet periods

Front 42

ice-jam floods

Back 42

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.

Front 43

dam-failure floods

Back 43

dams are built for flood protection; if a larger flood occurs, the dam is overtopped.

Front 44

factors that determine water velocity

Back 44

gradient, discharge

Front 45

aquifer

Back 45

rock or sediment through which groundwater moves easily.

Front 46

aquitard

Back 46

(confining layer) an impermeable bed that hinders or prevents groundwater movement (aqua=water, tard=slow). clay is a good example.

Front 47

capillary fringe

Back 47

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.

Front 48

gaining stream vs. losing stream

Back 48

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.

Front 49

karst

Back 49

a type of topography formed on soluble rock (especially limestone) primarily by dissolution. it is characterized by sinkholes, caves, and underground drainage.

Front 50

porosity vs. permeability

Back 50

porosity: the volume of open spaces in rock or soil.
permeability: a measure of a material's ability to transmit water.

Front 51

travertine

Back 51

a form of limestone that is deposited by hot springs or as a cave deposit.

Front 52

speleothems

Back 52

a collective term for the dripstone features found in caverns.

Front 53

stalactites

Back 53

the icicle-like structure that hangs from the ceiling of a cavern.

Front 54

stalagmites

Back 54

the columnlike form that grows upward from the floor of a cavern.

Front 55

sinkholes

Back 55

a depression produced in a region where soluble rock has been removed by groundwater.

Front 56

water table

Back 56

the upper level of the saturated zone of groundwater.

Front 57

zone of aeration

Back 57

the area above the water table where openings in soil, sediment, and rock are not saturated but filled mainly with air.

Front 58

zone of saturation

Back 58

the zone where all open spaces in sediment and rock are completely filled with water.

Front 59

why groundwater is important

Back 59

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).

Front 60

how the level of the water table can vary naturally and by humans

Back 60

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.

Front 61

why springs flow

Back 61

1. gaining streams
2. losing streams
3. combination (streams gains in some sections and loses in others)

Front 62

formation of hot springs and geysers

Back 62

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.

Front 63

artesian wells

Back 63

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.

Front 64

problems with pumping groundwater and its implications

Back 64

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

Front 65

creation of caves

Back 65

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.

Front 66

beach drift

Back 66

the transport of sediment in a zigzag pattern along a beach, caused by the uprush of water from obliquely breaking waves.

Front 67

ebb current

Back 67

the movement of tidal current away from the shore.

Front 68

flood current

Back 68

the tidal current associated with the increase in the height of the tide.

Front 69

longshore current

Back 69

a nearshore current that flows parallel to the shore.

Front 70

shoreline erosional and depositional features

Back 70

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).

Front 71

spring and neap tides

Back 71

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.

Front 72

wave refraction

Back 72

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.

Front 73

parts and measurements of waves

Back 73

crest- top of wave
trough- bottom curve
height- vertical distance between trough and crest
wavelength- distance between successive crests (or troughs).

Front 74

factors that determine wave features (height, length, period)

Back 74

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.

Front 75

impact of wave refraction

Back 75

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.

Front 76

human response to coastal erosion

Back 76

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

Front 77

causes of tides

Back 77

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.

Front 78

fall

Back 78

a type of movement common to mass-wasting processes that refers to the freefalling of detached individual pieces of any size.

Front 79

flow

Back 79

a type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid.

Front 80

slide

Back 80

a movement common to mass-wasting processes in which the material moving downslope remains fairly coherent and moves along a well-defined surface (landslide).

Front 81

factors that may increase the odds of having a mass wasting event

Back 81

increased slope, removal of vegetation (plants protect against erosion), earthquakes

Front 82

classification of mass wasting events by velocity

Back 82

most rapid type is called rock avalanche, but most do not move this quickly.

Front 83

classification of mass wasting events by type of material

Back 83

depends on whether the descending mass began as unconsolidated material or bedrock (terms like debris, mud, earth, or rock)

Front 84

classification of mass wasting events by type of motion

Back 84

fall, slide, or flow

Front 85

alluvial fnas

Back 85

a fan-shaped deposit of sediment formed when a stream's slope is abruptly reduced.

Front 86

bajadas

Back 86

an apron of sediment along a mountain front created by the coalescence of alluvial fans.

Front 87

desert pavement

Back 87

a layer of coarse pebbles and gravel created when wind removed the finer material.

Front 88

dunes

Back 88

a hill or ridge of wind-deposited sand.

Front 89

loess

Back 89

deposits of windblown silt, lacking visible layers, generally buff-colored, and capable of maintaining a nearly vertical cliff.

Front 90

perennial stream vs. ephemeral stream

Back 90

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.

Front 91

playas

Back 91

the flat central area of an undrained desert basin.

Front 92

playa lakes

Back 92

a temporary lake in a playa.

Front 93

ventifact

Back 93

a cobble or pebble polished and shaped by the sandblasting effect of wind.

Front 94

yardang

Back 94

a streamlined, wind-sculpted ridge having the appearance of an inversted ship's hull that is oriented parallel to the prevailing wind.

Front 95

two types of deserts based on the amount of precipitation

Back 95

1. desert
2. steppe (a more humid variant of the desert)

Front 96

role of surface water in deserts

Back 96

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.

Front 97

mechanisms of wind erosion

Back 97

1. deflation (the lifting and removal of loose material).
2. abrasion (windblown sand cuts and polishes exposed rock surfaces).

Front 98

factors that determine shape of dunes

Back 98

wind direction and velocity, availability of sand, and the amount of vegetation present.

Front 99

calving

Back 99

wastage of a glacier that occurs when large pieces of ice break into the water.

Front 100

crevasses

Back 100

a deep crack in the brittle surface of a glacier.

Front 101

firn

Back 101

granular recrystallized snow. a transitional stage between snow and glacial ice.

Front 102

surges

Back 102

a period of rapid glacial advance. surges are typically sporadic and short-lived.

Front 103

icebergs

Back 103

a large floating mass of ice, detached from a glacier and carried out to sea.

Front 104

type of glaciers resulting from continental and mountainous glaciation

Back 104

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).

Front 105

types of glacial movement

Back 105

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).

Front 106

zone of fracture

Back 106

the upper portion of a glacier consisting of brittle ice.

Front 107

zones in glacial budget

Back 107

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).

Front 108

mechanisms of glacial erosion

Back 108

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).

Front 109

results of glacial abrasion

Back 109

rock flour is produced; glacial striations

Front 110

names and formation of the landforms resulting from glacial erosion or deposition

Back 110

1. glaciated valleys
2. aretes (sharp-edged ridges) and horns (sharp pyramid-like peaks)
3. roche moutonnee (an asymmetrical knob of bedrock)

Front 111

atmosphere

Back 111

the gaseous protion of a planet, the planet's envelope of air.

Front 112

atmospheric science

Back 112

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.

Front 113

climatology

Back 113

the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences.

Front 114

meteorology

Back 114

the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.

Front 115

Ferrel cell

Back 115

usually shown between the Hadley and Polar cells. the main 'problem' with the Ferrel cell is that it is thermally indirect.

Front 116

Hadley cell

Back 116

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.

Front 117

Milankovitch cycles

Back 117

the collective effect of changes in the Earth's movements upon its climate

Front 118

eccentricity

Back 118

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.

Front 119

obliquity

Back 119

(axial tilt); the inclination angle of a planet's rotational axis in relation to a perpendicular to its orbital plane.

Front 120

precession

Back 120

a change in the direction of the axis of a rotating object.