Unit 8_Lab_BeachSediment (1)
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Geology
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Dec 6, 2023
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Name ________Tyler Hope___________________
Date ______________11/1/23______________
Class Day/Time ___________________
Lab 8: A Tale of Two Beach Faces – Florida Beach Sediment Comparison Lab
As a student living in the state of Florida, you have likely experienced a sandy beach before.
However, you may not have recognized that there are some significant differences between the
beaches of the west coast, along the Gulf of Mexico and the East Coast, facing the Atlantic
Ocean. The sands of each of the beaches have different grain sizes, textures, and colors – why?
The laboratory exercise objective today is to recognize the major differences between provided
lab samples of sand from the west coast and east coast of Florida. Through this, you will also
relate these differences to wave action and the angle of the beach face at each of the respective
locations.
Beach Sand and the Wentworth Scale
Sand is a reference to a specific size of sediment, ranging between 1/16 and 2 millimeters in
diameter. Most beach sand, as much as 90%, is derived from sediment-carrying rivers that
deposit materials near the coast. As the heavier materials, such as gravel, are usually deposited
upstream, much of the smaller materials are prevalent closer to the coast. The finest material,
such as silt or clay, is usually suspended in the water and carried out to the open ocean. Once
deposited, sand on beaches are distributed by wave action and a process called “longshore drift,”
where sand is carried up shorelines since waves refract when approaching the shallow depths
adjacent to shorelines.
Quartz makes up a vast majority of beach surfaces, especially along the west coast of Florida as
it is a widely abundant material that is fairly resistant to weathering. Along the east coast,
however, the beaches contain a significant amount of carbonate materials, causing the sand to
look tanner in color, than the white sand of the west. Carbonates along the east coast are mostly
made up of broken pieces of shells that have been continuously broken down and rounded off by
waves.
To adequately measure grain size, a scale is used called the Wentworth Scale of Grain Size.
Familiarize yourself with this scale below:
Sieving
In order to measure the distribution of grain sizes
from a beach sample, we will undergo a process
called, “sieving” (s-iv-ing). A sieve (siv) is a
container with a mesh base that has specific sized
openings. Sieves are stacked on top of one
another, with the largest opening mesh sieve
stacked at the top and the smallest at the bottom.
Sediment is poured into the top of the stack and shaken, to allow for the sediment to settle and be
sorted by grain size. Once complete, the sieve set is separated, and each pan is compared to the
total sample size to determine the percentage of sediment across each size in the scale.
Data Display
A histogram is created to graph the frequency distribution of the sediment sample. In this lab,
you will create histograms to represent each of the sample – west coast and east coast.
The Beach Face – Angles
The slope of the beach, which is related to wave action, is referred to as the beach face. This
angle, which is measured from the horizontal, gives us clues about the sediment grain size and
the amount of wave action that occurs in the area. Beaches with a very shallow slope, typically
contains much finer sediment. This is because a lack of intense wave action means that the finer
sediment has not been carried away from the beach. Conversely, where beaches have courser
sediment, much of the finer materials have already been eroded away due to a significant amount
of wave action in the area.
Laboratory Procedures
1.
Record the sample name (west coast or east coast). Measure out exactly 100g of your
sample using the laboratory balance.
2.
Examine your sieve set - make sure they are free from loose sediment and that they are
stacked in order from largest opening size to smallest.
3.
Pour the sediment sample into the top of the set and shake it (back and forth, not up and
down) to allow the sediment to be properly sorted for approximately 15 minutes.
4.
Carefully separate your sieve set and measure the mass of each of the sieves separately.
Record your measurements in the table.
5.
Follow steps 1-4 for the other sample.
Lab Part 1: West Coast Sample
Starting Sample Mass (g): ________100.6________
A
B
C
D
Sediment Sample Grain Size
Mass (grams)
Mass (g) / Total
Sample Mass (g)
Column C x 100
(Percent of Total)
Gravel
>2mm
0.3
0.0029
0.29%
Very Coarse Sand
1-2mm
0.5
0.0049
0.49%
Coarse Sand
500 µm – 1mm
1.5
0.0149
1.49%
Medium Sand
250 µm – 500 µm
25.8
0.256
25.6%
Fine Sand
125 µm – 250 µm
67.8
0.673
67.3%
Very Fine Sand
<125 µm
4
0.039
3.97%
Note: 1 millimeter = 1000 micrometers
Calculate the sum of the masses in Column B: _____99.9__________
Calculate your percent error (100g (Original Mass) - Sum of Masses in Column B / 100g
(Starting Sample Mass) x 100 = ______69.5%_________
What could account for the change in mass (the percent error calculated) in the steps of the
laboratory exercise?
I believe that the variation in mass could be explained by the fact that some objects were far
lighter than others and perhaps the machine did not fully account for the weight because it
was so light.
Lab Part 2: East Coast Sample
Total Sample Mass (g): ________77.2_________
A
B
C
D
Sediment Sample Grain Size
Mass (g)
Mass (g) / Total
Sample Mass (g)
Column C x 100
(Percent of Total)
Gravel
>2mm
0.5
0.0064
0.64%
Very Coarse Sand
1-2mm
1.6
0.020
2%
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Coarse Sand
500 µm – 1mm
15.8
0.204
20.4%
Medium Sand
250 µm – 500 µm
46.4
0.601
60.1%
Fine Sand
125 µm – 250 µm
9.3
0.120
12%
Very Fine Sand
<125 µm
1.2
0.015
1.6%
Note: 1 millimeter = 1000 micrometers
Calculate the sum of the masses in Column B: _______74.8________
(100g (Original Mass) - Sum of Mass Column B / 100g (Starting Sample Mass) x 100 =
_______3.1%________
Data Analysis
Generate histograms for each of the two samples. Each row in the histogram represents 5%
of the total sample.
Histogram – West Coast Sample Grain Distribution
clay and silt
very fine
sand
fine sand
medium
sand
coarse sand
very coarse
sand
gravel
Histogram – East Coast Sample Grain Distribution
clay and silt
very fine
sand
fine sand
medium
sand
coarse sand
very coarse
sand
gravel
Analysis Questions
Compare and contrast the grain size distributions presented in your histograms for the two beach
samples.
The west coast sample seems to be mainly fine sand, with a bit of medium grained sand as well.
The east coast sample consists of
mainly medium grained sand, and a bit of coarse sand.
Based on grain size distribution and the pre-reading, describe the expected differences in wave
energy of both beaches.
From looking at the west coast sample, the wave energy along the west coast must be low
energy, considering that the sample is made up of mostly fine grained sand. The east coast
sample on the other hand, shows that the wave energy is slightly higher than the west coast, but
not that high as there weren’t many larger grain sizes, only medium.
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