Chapter 13 (running water)- Geology

water content of earths hydrosphere

-1.36 billion cubic kilometers

wide and shallow channel

-has a lot of frictional drag because so it has greater wetted perimeter -causing stream to go slower

gullies

-rills meet and form

oxbow lake

-the abandoned bend

zone of sediment production

- where most of the sediment is derived -located along the headwaters region of river system -sediment is compromised by the bedrock that is broken down by weathering and moved downslope -scouring the channel bed deepens the channels and adds to sediment load

cross sectional shape

-a slice taken across the channel -determine the amount of flow in contact with the banks and bed of the channel

flow velocity

-ability of a streams ability to erode and transport material is directly based off of -as velocity increases the stream flow becomes more turbulent -can change from place to place on river -strength of the current increased as you move deeper in the channel because the the greater fictional resistance near the banks and bed of the channel -determined ar gaging stations

stream terraces

-after a river had been flowing on a floodplain has then adjusted to a base level drop -it will start again producing a floodplain at a level below the original one

evapotranspiration

-both evaporation and transpiration involve the transfer of water from the surface directly to the atmosphere -often considered together as one process

rough

-channel can have boulders, irregularities in the channel bed and woody debris that can create

factors affecting flow velocity

-channel slope or gradient -channel cross sectional shape -channel size and roughness -discharge which is the amount of water flowing in channel

bed load

-coarse materials including coarse sands, gravel and even boulders typically move along the bed of a channel as a -they move by rolling sliding and saltation -moves much slower than the suspended load

stream valley

-consist of a channel and the surrounding terrain that directs water to the stream -includes the valley floor and valley walls -can be narrow steep valleys or very flat broad valleys

floodplain

-continuous lateral erosion caused by shifting meanders gradually produces a broad flat valley floor covered in alluvium -it becomes inundated when the river overflows its banks during flood stage -overtime it will widen so much that the stream is now only eroding some parts of the valley walls

bedrock channels

-cut into underlying strata and typically form in the head waters of river systems where streams have steep gradients -streams actively cutting into solid rock -streams tend to exhibit winding or irregular patterns -often contain steps and pools -tend to be located in narrow v- shaped valleys

settling velocity

-defined as the speed at which a particle falls through a still fluid -the larger the particle the faster it will settle -flat grains sink slower than spherical grains

zone of sediment transport

-downstream from the zone of sediment production -sediment acquired by the stream in transported through the channel network called trunk streams

base level

-downward limit to stream erosion -defined as the lowest elevation to which a stream can erode its channel -the level where the mouth of the stream enters the ocean

divide

-each drainage basin is bounded by imaginary line -clearly visible sharp ridge in some areas -the ridge can separate small gullies or even huge continents

cut off

-eventually the river may erode threw a narrow neck of land forming a new shorter channel segment called

drainage basin (watershed)

-every stream drains an area of land called -

rectangular pattern

-exhibits many right angle bends -pattern develops when the bedrock is criss crossed by a series of joints and fractures

sorting

-explain why particles of similar size are deposited together -when the larger particles settle first

headward erosion

-extending the heads of their channels upslope -the surface flow at the head of the channel has enough power to cut the channel deeper -the valley extends into previously undirected terrain

potholes

-features common to some bedrock channel that are circular depressions -created by abrasion action particles swirling in fast moving eddies

alluvial channels

-form in sediment that was previously deposited in the valley -banks and beds are composed of alluvium, they can undergo significant change in shape because material is constantly being eroded, transported and deposited -often flow in valleys that have wide valley floors consisting of sand and gravel

alluvium

-general term for sediment deposited by streams

river

-general term for streams that carry substantial amounts of water and have numerous tributaries

US geological survey

-has 7500 stream gaging stations -collect data about flow velocity, discharge and river stage

narrow deep channel

-has less frictional drag and will flow more rapidly -most efficient channel

water moves along all 4 of earths spheres

-hydrosphere -biosphere -atmosphere -geosphere

storage of water in glaciers

-if precipitation falls in areas at high elevation or high latitudes -the water may not immediately soak in, run off or evaporate -the water may become part of a snowfield or glacier

local or temporary base level

-includes level of lakes, resistant layers of rocks, and rivers that act as base level for tributaries

river system

-includes network of stream channels and the drainage basin -can be divided into 3 zones 1-zone of sediment production 2-zone of sediment transport 3-zone of sediment depostion

most precipitation does one of two things

-infiltrate(sink in ground) -run off

point bars

-inside of meandering channel -since its on the inside of the meander channel the water is going slow and depositing material along

runoff vs. infiltrate depends on several things

-intensity and duration of rainfall -amount of water already in the soil -nature of surface material -slope of land -vegetation

drainage systems

-interconnected networks of streams that exhibit many patterns

quarrying

-involves removal of blocks from the bed of a stream channel -process is aided by fracturing and weathering the rocks of the bed so they can be moved

capacity

-maximum load of solid particles a stream can transport per unit time -the greater the discharge then the greater capacity

two types of alluvial channels

-meandering channels -braided channels

competence

-measure of a streams ability to transport particles based on size rather than quantity -flow velocity is key -fast streams carry larger particles

largest drainage basin in north America

-mississippi river -collecting and carrying 40 percent of flow in the US

dendritic pattern

-most common drainage pattern -ressembles the branching pattern of a deciduous tree -forms when the underlying material is relatively uniform in its resistance to erosion and hence doesn't control the the pattern of stream flow -determined by the direction of slope of land

turbulent flow

-most streams expiernce this type of flow -strong turbulent behavior occurs in whirl pools and rolling white water rapids -even streams that appear smooth on the surface, still expierence this flow at the bottom -the turbulence acts to erode the channel because it can lift sediment

graded stream

-observing streams that adjust their profiles to changes in base level -necessary slope other channel characteristics to maintain the minimum velocity required to transport the material supplied to it -on average usually just transporting material

deposition

-occurs when a stream slows down causing reduction in competence -when the flow of velocity is less than the settling velocity -largest particles settle first

where water is located on earth

-oceans -glaciers -rivers -lakes -air -soil -living tissue

stream channel

-open conduit consisting of the stream bed and banks that act to confine the flow except during floods

cut bank

-part of meandering channel -outside of meander zone is active erosion area because the water is traveling faster

sandy channel

-particles are easily dislodged from the bed and banks and then lifted into moving water -usually undercut dumping even more loose sediment into streams -usually wide channels because lots of erosion is happening

coarse gravel or clay channels

-particles tend to be resistant to erosion -generally narrow channels because not much erosion is happening

infiltration

-portion of the water soaks into the ground -slowly moving downward then moving laterally and then finally seeping into lakes, streams or oceans

abrasion

-process by which the bed and banks of bedrock channel are ceaselessly bombarded by particles carried into the flow -bumping scratching rubbing of the particles erodes a bedrock channel

corrosion

-process in which rock is gradually dissolved by the flowing water -bedrock channels formed in soluble rock such a limestone are susceptible to... -type of chemical weathering

streams cut channels into bedrock through 3 different processes

-quarrying -abrasion -corrosion

trellis pattern

-rectangular drainage pattern in which tributary streams are nearly parallel -develops in areas of alternating weak and resistant bedrock

slot canyons

-regions where weathering is slow and rock is resistant -narrow valleys having nearly vertical walls -formed by the wear of water rushing through rock. A slot canyon is significantly deeper than it is wide

ultimate base level

-sea level

saltation

-sediment that appears to jump or skip along the stream bed -the sediments get lifted by current and are carried downstream a little and then gravity pulls them back down -sediments that are to large for this usually roll or slide on the bottom

longitudinal profile

-simply a cross section view of the stream from its source area (head) to the mouth where it dumps into another body of water -useful way of studying a stream -

immense volume of moving water

-single most important agent sculpting earths land surfaces

incised meanders

-some rivers have meandering channels that flow in steep, narrow bedrock valleys -means to cut into -can occur when the river is originally on a floodplain but the land starts to uplift and the river starts to downcut -a river meander that has been cut abnormally deeply into the landscape because uplift of the land has led to renewed downward erosion by the river

braided channels

-some streams consist of complex network or channels that thread their way among numerous islands or gravel bars -these channels have interwoven appearance -very common to see form at the end of glaciers -when the channel flow slows down deposition occurs and bars form -the bars split the path of the water

transpiration

-some water that soaks into the ground is absorbed by plants -then the plants release the water back into the atmosphere

v shaped valley

-steep sided walls formed by downcutting -most prominent features include rapids and waterfalls

water gap

-steep walled notch followed by a river -a transverse gap in a mountain ridge through which a stream or river flows

superposed stream

-streams cut across structures, they dont flow around them -eroded its channel into an existing structure -rivers take their courses with out regard to structures below

meandering channels

-streams that transport much of their load in suspension generally move in sweeping bends called meanders -flow in deep smooth channels -primarily transport mud, silt, sand or clay - individual bends migrate across the floodplain

runoff is dominant process

-surface material is impermeable -becomes to saturates -high slopes are steep -if areas are cover in concrete

wetted perimeter

-take a cross sectional shape -look at the amount of contact the water has with the banks and bed

river stage

-the height of the water surface relative to a fixed point

downcutting

-the lowering of the stream bed toward base level

discharge

-the measure most often used to compare the size of streams -the volume of water flowing past a certain point given a unit of time -measured by multiplying the streams cross sectional area by the velocity -when this increases so does the width, depth, and flow

mouth

-the point down stream where it empties into another water body -the gradient becomes less steep as it gets closer to the mouth

evaporation

-the process by which liquid water changes into water vapor(gas) -how ater enters the atmosphere from the ocean

gradient

-the slope of the stream channel -expressed as the vertical drop of a stream over a distance -when the gradient is steeper the more gravitational energy is available to drive channel flow

hydrologic cycle

-the unending circulation of water -energy source comes from the sun

water balance

-the volume that passes through each part of the water cycle annually -the hydrologic cycle is balanced -the total amount of water vapor remains the same, the average annual precipitation must be equal to water evaporated

stream erosion

-they have the ability to down cut and widen channels and they can transport wide amounts of sediment -its ability to transport is aided by raindrops that know sediment loose -when the ground is saturated it cant infiltrate and there for the water runs off transporting material it carries with it

settling velocity and flow velocity

-type and amount of material carried in suspended load depend on

dissolved load

-type of stream transport -brought to a stream by groundwater and is dispersed throughout the flow -when water goes through the ground it percolates small soluble soil compounds and carries around the dissolved mineral matter -velocity of stream flow has no effect on the streams ability to carry dissolved load -(invisible)

radial pattern

-typically develops on isolated volcanic cones and uplifts -type of drainage pattern

capacity and competence

-used to describe a streams ability to carry solid particles

suspended load

-usually streams transport the greatest amount of sediment here -usually only carries very fine sand, silt and clay particles -causes water to become muddy and murky -but during flood stage larger particles can be carried by this load -moves at a fast rate

downstream

-usually the further downstream you get the more water you get because of tributaries feeding into the channel - channel size typically increases as well because of the growing amount of water -also sediment grain is relatively smaller making the channel smooth and efficient

laminar flow

-very slow moving streams -water moves in nearly straight line paths parallel to stream channel

hill slope erosion

-water erosion on the hill slides -water flows down the hill of the drainage basin into the stream -main source of fine clay and sand particles carried into stream channels

stream

-water that flows in a channel regardless of size

bankful

-when a stream is so full but not yet flooding the floodplain -the maximum flow velocity occurs when the stream is at this stage

sheet flow

-when run off water starts flowing -it flows in broad thin sheets

rills

-when runoff water flowing in a sheet flow forms a small current that forms tiny channels called

run off

-when the rate of rainfall exceeds the grounds ability to absorb it -the surplus water flows over the surface into lakes, streams -flows if broad, thin sheets

zone of sediment deposition

-when the river approaches an ocean it slows and the energy to transport is gradually reduced -most of the sediments accumulate at the mouth of the river to form a delta

precipitation

-when water falls out of the moist air (clouds) -the water that falls straight back in the ocean has completed its cycle and is ready to start again -the water that falls on continents must make its way back to the ocean

head or headwaters

-where the stream starts -the source area

start and finish of water

1-runoff 2-sheet flow 3-rills 4-gullies 5-streams 6-rivers

2%

percentage of water divided among lakes, streams and ground water

1.76%

percentage of water stored in glaciers and ice sheets

96.5%

percentage of water stored in the global oceans