AHS Science Question

Name ___________________________Date ____________________________
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.
*For this lab note the initial mass shown in the demonstration video
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): _________________
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
Very Coarse Sand 1-2mm
Coarse Sand 500 µm – 1mm
Medium Sand 250 µm – 500 µm
Fine Sand 125 µm – 250 µm
Very Fine Sand 2mm
Very Coarse Sand 1-2mm
Coarse Sand 500 µm – 1mm
Medium Sand 250 µm – 500 µm
Fine Sand 125 µm – 250 µm
Very Fine Sand