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Geology 161 Final > ch10 flashcards > Flashcards

ch10 flashcards

(65 cards)

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1
Q

hydrologic cycle

A

The continuous movement of water on, above, and below Earth’s surface through processes like evaporation, condensation, precipitation, infiltration, and runoff

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2
Q

overland flow

A

Water flowing over the land’s surface before entering a stream channel; occurs as sheetflow (thin layers) or rivulet flow (small, concentrated channels)

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3
Q

sheetflow

A

A thin, uniform layer of water moving over the ground surface, typically formed after rainfall before water collects into channels

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4
Q

rivulet flow

A

Overland flow that becomes concentrated into small channels or rivulets, often leading to the formation of stream channels

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5
Q

stream discharge (Q=AV)

A

The volume of water flowing past a point in a channel per unit time, calculated as the product of cross-sectional area (A) and velocity (V)

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6
Q

flood hydrograph

A

A graph showing how a stream’s discharge changes over time during and after a precipitation event, illustrating lagtime and peak discharge

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7
Q

lagtime

A

The time delay between peak rainfall and peak stream discharge, influenced by factors like vegetation, soil permeability, and urbanization

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8
Q

valley enlargement

A

The process by which stream valleys grow larger over time through downcutting (deepening), headward erosion (lengthening upstream), and widening of valley walls

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9
Q

downcutting

A

The process by which a stream erodes its channel bed, deepening the valley and lowering its base level

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10
Q

headward erosion

A

The upstream extension of a stream channel by erosion at its head, capturing new drainage areas and lengthening the stream

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11
Q

widening

A

The lateral erosion of stream banks that broadens the valley, often caused by increased meandering and undercutting

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12
Q

stream erosion

A

The removal of rock and soil by moving water, primarily through hydraulic action, abrasion, and solution

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13
Q

hydraulic action

A

The erosive force of moving water as it exerts pressure, lifts and removes loose sediments, and enlarges cracks in rock

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14
Q

abrasion (in streams)

A

Erosion caused by the grinding action of sediment and rock fragments carried by the stream acting like sandpaper on the channel bed and walls

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15
Q

dissolved load

A

The portion of a stream’s load composed of soluble minerals dissolved in the water

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16
Q

suspended load

A

Fine sediment (clay, silt, and fine sand) carried in suspension by the turbulence of the water, giving the stream a muddy appearance

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17
Q

bed load

A

Coarser particles (sand, gravel, pebbles) that move along the stream bed by rolling, sliding, or hopping (saltation)

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18
Q

competency

A

A measure of the largest particle size a stream can transport; increases with velocity and discharge

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19
Q

capacity

A

The total amount of sediment a stream can carry, depending on its discharge and velocity

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20
Q

stream velocity

A

The speed of water flow in a channel, influenced by gradient, channel shape, sediment load, and water volume

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21
Q

stream gradient

A

The slope or steepness of a stream channel, generally decreasing downstream and affecting flow velocity and erosion

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22
Q

channel shape

A

The geometry (width, depth, roughness) of a stream’s channel, influencing flow resistance, velocity, and sediment transport

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23
Q

sediment load

A

The total amount of sediment (dissolved, suspended, and bed load) carried by a stream at any given time

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24
Q

water volume

A

The amount of water in a stream (discharge), impacting its ability to erode, transport sediment, and shape the landscape

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25
drainage patterns
The arrangement of streams and tributaries in a region, influenced by underlying geology; common types include dendritic, rectangular, trellis, radial, braided, and deranged
26
dendritic pattern
A tree-like drainage pattern with branching tributaries common in areas of uniform rock type
27
braided stream
A stream with multiple intertwined channels separated by bars and islands of coarse sediment, often found in areas with variable discharge
28
rectangular pattern
A drainage pattern characterized by numerous right-angle bends, formed where underlying bedrock is heavily jointed or faulted
29
trellis pattern
A drainage pattern with parallel main streams intersected by short tributaries at right angles, often in areas of folded or tilted rock layers
30
radial pattern
Streams radiate outwards from a central high point (like a volcano or dome), flowing away in all directions
31
deranged pattern
A chaotic drainage pattern with no clear overall structure, often in recently glaciated landscapes
32
stream piracy
The diversion of water from one stream into another due to headward erosion, capturing the headwaters of the adjacent drainage basin
33
beheaded stream
Streams that have lost their original headwaters due to stream piracy, leaving them shorter and with reduced discharge
34
floodplains
Flat areas bordering a stream channel that are periodically inundated with floodwaters, depositing alluvium and forming features like meanders and oxbow lakes
35
meander
A broad, sweeping bend in a river channel that migrates laterally due to erosion on the outer banks (cutbanks) and deposition on the inner banks (point bars)
36
cutoff
A new, shorter channel formed when a stream cuts through a narrow strip of land between meander bends, isolating an old meander loop to form an oxbow lake
37
cutbank
The steep, eroding outer bank of a meander where flow velocity is higher, causing more erosion
38
oxbow
A crescent-shaped lake formed when a meander loop is cut off from the main channel
39
yazoo stream
A tributary that flows parallel to the main river within the floodplain for some distance because natural levees block it from joining the main channel
40
natural levee
A ridge of coarse sediment deposited along the banks of a river channel during floods, confining future floodwaters to the channel
41
alluvial fan
A fan-shaped deposit of sediment formed where a stream’s gradient decreases rapidly as it leaves a mountainous area and enters a flatter valley
42
delta
A sediment deposit formed where a river enters a standing body of water, losing velocity and depositing sediment in various shapes (wave-dominated fan, river-dominated birdfoot, tide-dominated forms)
43
fan (wave-dominated) delta
A delta shape formed where wave action redistributes sediment more evenly along the coastline, creating a relatively smooth, fan-like shoreline
44
birdfoot (river-dominated) delta
A delta shape formed where the river’s input of sediment overwhelms other factors, creating a network of distributaries that resemble a bird’s foot
45
tide-dominated delta
A delta shape influenced heavily by tidal currents, producing numerous tidal channels and sand bars aligned with the tidal flow
46
bar
An accumulation of sediment, such as sand or gravel, formed in a stream channel or along a shoreline
47
base level
The lowest level to which a stream can erode its channel, generally at sea level or the level of the body of water into which it flows
48
discharge
The volume of water flowing in a stream at a given location and time, often expressed in cubic meters or cubic feet per second
49
distributary
A channel that branches off from the main stream channel in a delta, distributing water and sediment into separate paths
50
divide
A topographic high that separates adjacent drainage basins, determining which way water flows
51
drainage basin
The area of land from which a stream collects its water, bounded by divides
52
floodplain (alternative definition)
The flat valley floor adjacent to a stream, built up by sediment deposited during floods, and prone to periodic inundation
53
graded stream
A stream that has reached a delicate balance between erosion and deposition, maintaining a smooth, concave longitudinal profile over time
54
headward erosion (alternative definition)
The erosional extension of a stream’s channel upstream, increasing the length of the drainage network
55
incised meander
A meander that has cut deeply into the landscape, often due to uplift of the region or a drop in base level, resulting in steep, canyon-like walls
56
lateral erosion
The sideways erosion of a stream channel, widening the valley and shaping the floodplain
57
meander cutoff (alternative definition)
The process by which a river creates a shorter path by cutting through a narrow neck of land, leaving the old meander as an oxbow lake
58
point bar
A deposit of sediment on the inside of a meander bend, where velocity is lower, encouraging deposition
59
saltation
A mode of sediment transport in which particles bounce or hop along the stream bed, lifted briefly by turbulence
60
sheetwash
A thin layer of unchanneled water flowing over a land surface, contributing to soil erosion and the initial stages of channel formation
61
solution (in streams)
The process by which soluble minerals dissolve in water, becoming part of the dissolved load transported by the stream
62
stream
A body of flowing water confined to a channel, varying in size from small creeks to large rivers
63
stream channel
The physical confines of a stream, including its bed and banks, where water typically flows
64
traction
The process of sediment particles (usually large clasts) rolling or sliding along the stream bed, never fully leaving contact with it
65
tributary
A smaller stream or river that flows into a larger one, contributing its water and sediment to the main channel

Geology 161 Final (13 decks)

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