German_Sediment
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Geology
Date
Dec 6, 2023
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Sediment lab
Elizabeth German
Lab Partners: Tehya Fulcher, Otto Martinez, & Brandon Sheetz
Lab preformed: 01/30/2023
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Abstract:
This laboratory experiment consisted of four different sections, during the first section a
sediment sample collected from the Everglades was mixed with 1800ml of tap water in a
graduated cylinder to observe the sinking rate of the sediment. From this section, it was observed
that different particles have different sinking individual rates and can even be suspended within a
water column. During the 2nd section of the lab, different objects were used to simulate sediment
particles typically found in the Everglades water columns to determine their sinking rates,
through this it was determined that Larger dense particles were found to sink faster while less
dense particles either sank slower or did not sink at all. In the 3rd section of the lab, the
disbursement of different-sized particles was observed by placing fine, medium, and coarse
sediment samples in tap water. Once the sediment sample was fully submerged an artificial
current was then made to observe the disbursement patterns of the sediments. The fine sediment
sample had a lot of movement and settled to form a bedform pattern, while the medium and
coarse sediment had little to no movement from the artificial current and did not form a bedrock.
In the final section of this lab, different sediment samples were observed under a transmitted
light microscope. The samples were then sorted into 3 categories lithogenic, biogenic, &
authigenic based on their key characteristics, there were 3 lithogenic, 2 biogenic, and 0
authigenic sediment samples observed.
Introduction:
Throughout the first section of the lab, the Stokes' Law equation was used to estimate a particle's
sinking rate in water. The Stokes’ Law predicts the velocity of a falling object inside a water
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column by taking the difference in density of the object and the water while squaring the
diameter. It is then multiplied by gravity and divided by 18 times the viscosity of water. The
equation is depicted as:
V
=
D
2
(
P
P
−
P
F
)
g
/
18
n
.
The smaller a particle is the slower it will
sink because of this; larger particles are deposited faster and reach the bottom first. These
particles in a real-life scenario such as whether rock particles falling into bodies of water would
be found closer to the shore while smaller particles are found further from land and deeper in the
ocean. During the 2nd section of the lab, the Stokes' Law equation was also used to determine
the sinking rate of objects of different densities, supporting the observations recorded in the first
section. The higher the density of the object dropped into the water column the faster it reached
the bottom, both the first and second sections of this lab were small-scale examples of what
happens to sediment in real large-scale bodies of water. The 3rd section of this lab focused on
how current patterns affect the disbursement of sediment across the sea floor. The more velocity
the current has the more disbursement will occur. This happens when the gravitational force on
the particles keeping them in place is weaker than the current in the water. The amount of force
required to entrain particles differs based on the size and density of the particle. Small particles
such as silt and clay can require a stronger current to move them as the electrical attraction
between them helps them stay attached to the sea floor. Particles that are entrained by a current
normally do not stay suspended for long and are gradually transported by the current through
multiple entrainments. Causing bedform occurs if the current that moves the particles is constant
for a long enough time, which was seen in the fine sand mixing but not in the medium or coarse
sands evaluations. Providing a range of how strong current patterns need to be moved and
redeposit varying sizes of sediment throughout the ocean. In the last section of this lab was
observing the differences in sediment among different areas in the world. The three main types of
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sediment: are biogenic, lithogenic, and authigenic, and how to determine them based on key
characteristics. Biogenic sediment is made from a living organism, lithogenic sediment is
sediment derived from rocks, and authigenic sediment is formed from dissolved minerals. These
types of sediment can be differentiated when observed under a microscope.
Materials & Methods:
Materials needed for the first section of this lab include: 100ml of Everglade sediment, 1800ml
of tap water, a stopwatch, and a 2-liter glass graduated cylinder. Then add the 1800ml of tap
water into the 2-liter graduated cylinder, once the water is inside placing the 200 milliliters of
Everglade sediment into the 1800ml of tap water. Once the sediment was completely settled to
the bottom, the graduated cylinder was then inverted and slightly shaken to disperse the sediment
throughout the makeshift water column. Then placed back in its original position a stopwatch
was then started. After 1-minute the amount of sediment that had settled on the bottom was
observed and recorded in cm for a total of 5 consecutive minutes. After the 5-minute period, the
amount of sediment settled at the bottom was recorded every 15 minutes for a total of 2 hours.
From this section of the experiment sediment fall rate was recorded to have a mean of: 3.4cm
and a standard deviation of: 0.62cm. Materials needed for section 2 of this lab include: a
stopwatch, a 1-liter graduated cylinder, tap water, a ruler, forceps, and various particles of
different densities (led ball, gravel, sand, plastic square, plastic circle, paper circle, & jewel). The
graduated cylinder was filled nearly to the top with tap water and each object's density(g/cm3)
length(cm) was measured. The objects were then placed on the surface of the water and dropped
in the forceps as their failure rate was recorded with the stopwatch. Every particle was timed at
least three times to ensure more accurate results, the fall rate mean of the objects dropped was
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6.51 (seconds/millisecond) and a standard deviation of: 7.63(seconds/millisecond). This section
of the lab supports the Stokes' Law equation as the objects with a higher density fell at a faster
rate than the lower-density objects. In the 3rd section of the lab materials needed include a large
spoon, a stopwatch, tap water, and three different types of sediment (fine, medium, and coarse
sand). Each type of sediment was placed into different glass basins and then filled with tap water.
The amount of water was then measured(cm) and recorded. Each water basin was then stirred
with a large spoon on the surface in a circular motion at a constant rate. The rate of stirring was
slowly increased allowing disbursement to occur within the sediment particles. Once the
particles began to lift from the bottom of the basin a stopwatch was started, and the stirring rate
was kept constant for a minute. The observation was then recorded for each of the sediment types
yielding a mean of 84.6(fine sediment), 88.3 (medium sediment), 56.3 (coarse sediment) in
circles per minute, and a standard deviation of 6.42(fine sediment), 1.53(medium sediment),
3.51(coarse sediment) in circles per minute. In the final section of the lab materials needed
include various sediment samples and a transmitted light microscope. Placing each slide under
the microscope, focusing it, and determining whether each sediment was lithogenic, biogenic, or
authigenic based on their key characteristics, the type of sediment can help determine what
location the sediment can be found in. There were 3 lithogenic (Volcanic sand Bail, Prince
Edward Island, and Hawaiian black sand), 2 biogenic (Waikiki beach & Acadia N.P. barharbor),
and 0 authigenic sediment samples observed.
Results:
Section #1 results: After 1 minute 100 milliliters of tan/brown sediment settled at the bottom of
the 2-liter graduated cylinder. Larger black and brown particles then began to settle on top of the
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first layer of sediment. The water appeared murky and opaque with a brown colored tint
appearing through the graduated cylinder. Many different particles could be seen floating
throughout the water column. After checking the sediment fall every 1 minute for 5 minutes
around 2.8cm of sediment have settled on top of the previously settled dark brown sediment. The
water remained a dark brown color with large particles still being visible floating within the
water. But overall, the water has slightly cleared up compared to the starting point. After the 5
minutes, the wait time was increased to every 15 minutes. After the first 15-minute check the top
of the water column has begun to clear up slightly more than the rest. Large particles remain
throughout the entirety of the water column. Some particles are stuck on top of the water's
surface, resting at 3.5cm of sediment fall, that number then gradually increased as the 15-minute
interval continued for the 2 hours, rising from 2.5cm to 4.1cm having an overall mean of 3.4 and
standard deviation 0.62 of. At this point, the water quality appeared to be mainly clear as no large
particles remain suspended within the entirety of the graduated cylinder and the water overall
was a light brown shade with it being mostly clear at the top. Section #2 results: The water depth
for this section of the laboratory experiment was 38.6±.10 and stayed this depth for the entirety
of the experiment section. The lead balls had a diameter of .6±0 cm and took .43±.22 seconds to
fall with a velocity. The gravel had a diameter of 2.5±1.2 cm and took .1.10±.06 seconds to fall
with a velocity of 41.72±3.24 cm/sec. The sink velocity as predicted by stokes law comes out to
be 12.19 cm/sec. The sink velocity as predicted by stokes law comes out to be 14.09 cm/sec. The
sand had a diameter of .8±0 cm and took .41±.20 seconds to fall with a velocity of 104.14±42.81
cm/sec. The sink velocity as predicted by stokes law comes out to be 18.07 cm/sec. The plastic
squares had a diameter of 1.5±0 cm. The particles were unable to sink on any of the trials. The
plastic circle had a diameter of 1±0 millimeters and took 7.60±2.62 seconds to fall with a
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velocity of 5.49±1.63 cm/sec. The sink velocity as predicted by stokes law comes out to be 58
cm/sec. The paper circles had a diameter of .7±0 cm and took 24.27±.5.86seconds to fall with a
velocity of 1.65±.36 cm/sec. The sink velocity as predicted by stokes law comes out to be 19.21
cm/sec. Section #3 results: For the fine sediment particles, the depth of the tap water was 3.3 ± 0
cm. 90 circles of rotations were completed in a minute once entrainment started. The fine
sediment took little effort to disperse but once the particles picked up from the bottom it was
easy to keep them in the current. After the particles were left to settle a bedform in a spiral
pattern(counter-clockwise) was formed within the sediment in the same direction the stirring was
going. For the medium sediment particles, the depth of the tap water was 3.1± 0 cm. At 87 circles
of rotations were completed in a minute once disbursement started. Particles did not move as
easily as the fine sediment did. Once the stirring stopped particles settled fairly quickly and no
pattern was formed. For the coarse sediment particles, the depth of the tap water was 3.1 ±0
centimeters. 60 circles of rotations were completed in a minute once dispersion started, in the
sediment mixture there was a variety of sized particles ranging from small/fine to large/coarse.
The smaller particles were more easily dispersed while the larger ones took more force. Once the
stirring stopped the particles settled quickly and no bedform formation was formed. Section #4
results: In the Volcanic sand Bail sediment sample, you can see variously sized and shaped
sediment fractures. The sediment particles are also of different colors and textures. Small shell
particles are visible in this sample. In the Prince Edward Island sediment sample, the sediment
looks glassy and transparent and the sediment particles have a slight orange/tan hue to them.
Only lithogenic sediment is visible within the sample. The sample of sediment from Hawaiian
black sand shows particles that are completely transparent and small. There is no biogenic
sediment in this sample as everything picture is the same. This sample displays authigenic
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material, which is why the last 3 samples were identified as lithogenic. While the Acadia N.P.
barharbor main sample is a prime example of biogenic sediment. The sediment within the shot is
small fragments of sediment that were produced from living organisms such as shell particles.
There are varying shapes and colors that can be seen in multiple types of sediment are visible
such as lithogenic, which is why this sample was defined as biogenic. The sediment from
Waikiki Beach is of differing sizes, shapes, and colors. Shell fragments can be seen as well as
lithogenic sediment of weather rock. The variety in this sample is the most of the five. This
sample primarily contains biogenic sediment.
Discussion:
In the first section of this laboratory experiment, both qualitative and quantitative observations
were recorded when observing 200 milliliters of Everglade sediment settling in a water column.
Because there were different particles within the sample, each one was sinking at a different rate.
This can be compared to the second part of the experiment where different objects were used to
represent real sample particles. Between these two parts, you can see similarities as the denser
particles are the faster they will sink whereas the lighter particles sank much slower or were
stuck suspended in the water column. By the end of the 2-hour interval, it appeared that all the
particles had settled out and there were no longer suspended in the water column. By observing
this sample, we were able to discover that larger denser particles settle to the bottom first and
lighter particles stay suspended just as marine snow does. For the 2nd section of this lab,
different particle sinking rates were tested. It was discovered that the denser a particle is the
faster its sinking rate will be and vice versa for lighter particles. The particles with density sizes
acted similarly to marine snow interacting with the water column as they floated down the
column slowly or did not sink at all. While other particles with higher density sizes particles did
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not interact much with the tap water but rather just sank to the bottom. The results obtained in
this portion were due to the varying densities and sizes of the particles and these results were
further supported by the Stokes’ law equation predicting higher velocity rates for the higher
density objects such as the led ball and jewel. For the 3rd section of the lab, the stirring rate
required to disperse different types of sediment were tested. In this section, the fine sand was
able to be easily dispersed and then created a bedform pattern that followed the shape of the
current. The sand ended in a counter-clockwise spiral as that was the way the current was going.
As the current increased the bedform became more pronounced. In the sediment sample for the
medium and coarse sediments, no bedform pattern was created. This part of the lab was able to
show that larger particles cannot form bedform patterns as easily as fine sediment can. Larger
sediments also need a stronger current to be able to disperse larger particles as the force keeping
them on the bottom is stronger and must be overcome by the current. In the final section of this
experiment sediment samples from five different locations were examined under a microscope.
These samples were then observed to see the differences within their makeup. Lithogenic,
biogenic, and authigenic samples were looked at and the characteristics of each were recorded.
Lithogenic sediment samples are primarily composed of small fragments of preexisting rocks
that have made their way into the ocean. These sediments can contain an entire range of particle
sizes, from microscopic clays to large boulders, and they are found almost everywhere on the
ocean floor. Biogenic sediment samples are sediment that contains more than 30 percent skeletal
material. These sediments can be made up of either carbonate (or calcareous) ooze or siliceous
ooze. The skeletal material in carbonate oozes is calcium carbonate usually in the form of the
mineral calcite but sometimes aragonite. While authigenic samples are formed in place on the
seafloor. The most significant authigenic sediments in modern ocean basins are metal-rich
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sediments and manganese nodules. Metal-rich sediments include those enriched by iron,
manganese, copper, chromium, and lead. These sediments are common at spreading centers,
indicating that processes at the centers are responsible for their formation specifically,
hydrothermal circulation is the controlling factor.
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