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Earth Science Chapter 10


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where does most final deposition occur and why?
in large water bodies bc running water is the ost important erosional system
when does deposition occur?
when the velocity of the stream,, wind, or other erosional system decreases or just stops moving
what two factors affect the rate of deposition?
the velocity of the erosional system and the characteristics of the sediments themselves
rate of stream in relation to size of particles it can carry
the faster a stream, the larger size particles it can carry
what happens when the speed of a stream drops below the speed it needs to carry certain sediments
the sediments are deposited
what aspects of sediments affect how fast they will be deposited in air or water environments
size, shape, density, and sautration of dissolved minerals
larger sdiments settle out first
because they are heavier and sink faster
the more rounded a sediment, the faster it will settle out
the more flattnened it is the greater its resistance to deposition
the higher the density, the faster it will settle out in air or water
affect of saturation of dissolved minerals
if evaporation, temp hanges, or increaes in amount of dissolved miinterals in a water body result in a saturated condition, the dissolved mineral or minerals will settle or precipitate out of the dissolved dontion and crystallize. as a result, rocks composed of one mineral can form
graded bedding
a sediment later formed when a mixture of seidment sizes in water settles out rapidy and a horizonal bed develops w/ sediment size decreasing from bottom to top
sediment-laden density currents
associated w/ graded bedding
most common of the sloped ocean bottoms off the coasts of continents and on a lake where flooding streams rapdily decrease inv elocity when they enter
which particles settle out first when the velocity of a wind or water erosional system gradually decreases?
the larger, denser, and more rounded rediments
what does this result in?
layers w/ horizonal sorting, in which sediemnt size, roundness, and density generally decrease in the direction toward which the erosional system was moving
explain horizontal sorting where a stream enters the ocean or lake forming a delta
the large sediments settle first (nearer the shore). sediments become smaller as distance from the shore increases.
what happens to the sediments when there is mass movement, such as a rock fall, landslide, or avalanche
the sediments are usually dumped together in a random deposit that is unsorted and unlayered, similar to glacial deposits
where does the stream have max. potential energy
at the source, or beginning, of the stream
what happens to the energy as the stream flows toward its mouth, or end?
potential energy is continuously being transformed into kintetic energy
where does the stream have its greatest velocity and greatest kinetic energy?
where the slope of the stream is steep
where is erosion dominant?
wherever the kinetic energy of the system is large?
where is deposition dominant?
where the kinetic energy is small
what regions does erosion occur in?
in regions of sleep slope or high discharge
what regions does deposition occur in?
regions of gentle slope or low dischage
where is deposition particularly rapid?
at the mouth of the stream, where the kinetic energy becomes zero
what would happen if one or more tributaries were to enter a stream?
it would increase the mass or discharge of water, thus increasing the potential energy of the stream. the velocity would increase, causing eriosion to increase and deposition to decrease
where do the interfaces between erosion and deposition exist?
at the meanders in the model stream
between the source and the mouth of a stream
may also be found where changes in slope occur
dynamic equilibrium
rate of erosion equals the rate of deposition by the stream as a whole
depositional agents
streams, glaciers, water waves and currents, wind, and mass movements
where does a stream deposit sediments?
sediments are deposited on the inside of the meanders where stream velocity is slow
a mound of sediments formed at the edge of a river when a stream floods and overflows its banks
where does most of teh sediemnt go when a stream floods and overflows its bnks?
it is spread over a relatively flat regions to the ssides of the stream forming a flood plain
deposition at the end of a stream with characteristic horizontal sorting
why might a delta not form is there are strong ocean or lake currents
bc the velocity of the water is not reduced enough at this location
unsorted piles where the sediments a glacier is carrying is dropped. it is at the end of a glacier where htere is a balance between melting and forward movement
ground moraine
a moraine that is a thin sheet deposited from the bottom of the glacier
what is moraine from?
direct glacier deposits
what do ground moraines cover?
much of northern US including much of NY state
terminal moraine
formed when a if the end of a glacier stays in one location for some time and the glacier builds up a pile of sediments
a feature similar to the shape of the end of an inverted spoon-formed if a flacier mounds up the grand moraine into a streamlined over shape
what does the drumlin indicate
the direction a claier came from by being oriented with direction of former glacier movement
how can u tell?
drumlines have steeper slopes pointing ot the direction the glaciers came from
kettle lakes
sometimes as a glacier melts back, it leaves block of ice in the terminal or grond moraine. when these blocks of ice melt, they leave behind circular depressions called kettle holes or kettles. if theese kettles intersect the water tables, they will become filled with water and then are claled kettle lakes
outwash plain
whenerver glaciers melt, running water will carry sediments from the glaciers to produce layered and sorted sediment deposits when the water slows down or stops. one such feature is an outwash plain-- a broad delta-like feature
a strip of sediment at teh coastline built up by wave movement towards the shore
what do varrier island often do for the shore?
protects it from pounding by storm waves
depositional feature formed by longshore currents transported sediment-sand, and when the velocity of water slows, deposition creates a sandbar
barrier island
if a sandbar rises about average sea level, winds will help to pile up the sediments. thne vegetation can stabilize this offshore seidment pile, creating a barrier island.
where are barrier islands common
along the east and southeast coast of the US
sediments smaller than sand (silt and clay)
what does wind usually tranpport and deposit?
only sand and smaller sized sediments
sand dunes
sand is deposited by wind if layers or in mounds called snad dunes
slope of sand dunes
have a gentle slop facing into the wind, and a steeper slope oin the side the wind is blowing towards
which way do sand dunes migrate?
in a body downwind--in the direction the wind is blowing to---creating layers of sloping sorted sediment.
what is the sand within the sand dunes like and why?
usually very rounded and frosted in appearance due to numerous collisions of sand grains during erosion
what are depositional features like when desidemts are deposited by mass movement like an avalance?
unsorted and unlayered sediemnts
what will the sediments look like?
not very rounded-sharp sides
what is the most recognizable depositional feature of mass movement ?
a pile of sediments that is the result of sediments often found at the base of cliffs
where does outwash plain come from
deposited mostly by water from melting glaciers
where down moraine come from
deposited by glaciers
where does drumlin come from
where does barrier island come from
waves and shore currents
where does sand dune come from
where does flood plain come from

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