Transcript The Size, Sorting and Roundness of Sand

The Size,
Sorting and
Roundness of
Sand
Energy Levels of Water
Moving water provides a large amount of energy that
is required to transport large sand grains.
In very still water there is insufficient energy to bring
larger sand grains into the environment.
.
The larger the size of the sand grains, the higher the
energy environment.
This is called a high-energy depositional environment.
The smaller the size of the sand grains, the lower the
energy environment.
This is called a low-energy depositional environment.
Moving water (waves or currents) – are
high-energy .
Quiet or still water – are low-energy.
Deep water has quiet water (low
energy) and a wave motion at upper
part of water high energy).
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Questions on Size
What would happen to the size of the sand grains in a
place where there is moving water (currents or waves)?
What would happen to the size of the sand grains in a
place where there is quiet or still water?
Size of Grain of Sand
The size of the sand grains indicates the
energy level where deposited (beach,
riverbed, lake, delta).
Faster-moving water is able to carry a larger
sand and rocks.
The larger the size of the sand grains, the higher the energy environment.
Slower-moving water is only able to carry
smaller grains.
Questions about Roundness
What would happen to the roundness of the sand
grains if they traveled a long distance and were in the
depositional environment for a long time.?
 What would happen to the roundness of the sand
grains if they traveled a short distance and were in the
depositional environment a short time?
Roundness
 Roundness is a measure of the sharpness or roundness of
the corners of the sand grains.
 As sand grains are transported, they undergo abrasion by
coming into contact with the stream bottom, sea floor, or
other grains.
 A well-rounded sand grain indicates that it has been
transported far from the original source area, and that it has
been in the depositional environment for a long time.
 Angular sand grains have probably only been transported
for a short distance from the source area, and it has been in
the depositional environment for a short time.
Roundness
Roundness can be determined by comparing
the sand grains to the following visual
comparison chart.
Sorting
Sorting refers to the range in grain sizes of the sand.
Sand that is well sorted will have most of the grains
roughly the same size.
Poorly sorted sand has a wide range of grain sizes.
Sorting can be estimated using the following visual
comparison chart.
Well-sorted grains indicate that the sand was
probably transported for a long time in a fairly highenergy environment (waves or currents).
 The finer grains were probably washed away.
 Good sorting implies consistent, fairly high energy
levels (washing).
Poorly sorted grains indicate that the sediment
has not been transported very far from the source
area.
 It also suggests fluctuating energy levels,
and a fairly short time in the depositional
environment.
Poor sorting implies inconsistent energy – rapid
dumping (which might involve short episodes of
high energy), followed by low energy conditions.
Weathering & Erosional
Deposition
The products of physical, chemical, and biological
weathering are the raw material for sedimentary rocks.
Erosion is the transportation of these materials,
usually by water, wind, ice, or gravity.
Weathered debris is eventually deposited in lakes,
river valleys, seas, and oceans.
Over long periods of time these sediments are
cemented together to form solid rock.