Geology Unit Lab Activity
Teacher Packet
Introduction:
In this activity you will examine samples of sediments and rocks (coral and beachrock) from
Florida. The properties of these samples can help us to determine their histories and origin,
and clues to what the Florida coast and its sea level were like in the past.
Materials:
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Metric Ruler
Magnifying Lens
Dilute Hydrochloric Acid
Petri Dishes for Samples
Samples for Analysis
o Sediment Samples from East Coast of Florida
o Sediment Samples from Florida Keys
o Sediment Samples from West Coast of Florida
o Coral Sample
o Beachrock Sample
Lab Handout
Lab Layout:
There will be five stations total that each of the students will need to visit. Each station will
have a duplicate setup, so the students can be broken down into ten groups (making small
group sizes). The groups will either be rotating odd or even numbered stations.
Station 1 and 2: Sediment samples from the east coast of Florida, Samples 1 and 2
Station 3 and 4: Sediment samples from the Florida Keys, Samples 3 and 4
Station 5 and 6: Sediment samples from the west coast of Florida, Samples 5 and 6
Station 7 and 8: Rock sample from the Florida Keys, Sample 7
Station 9 and 10: Rock sample from the east coast of Florida, Sample 8
One copy of pages 2-6 of the teacher packet should be at each station (to save color printing).
Each student or group will get a black and white copy the student packet.
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Vocabulary:
Rock: Rocks are composed of two or more minerals. They also can include remains of
plants, animals or other organisms.
Beachrock: A type of sedimentary rock composed of quartz sand and shell material
cemented together by calcium carbonate. The shell material and calcium
carbonate cement will react (bubble or effervesce) with application of
hydrochloric acid. The abundance of shell material is a strong indicator that the
rock is a beachrock.
The images above are beachrock found on South Hutchinson Island in south Florida on
the east coast. The top layer of the beachrock is interpreted as a fossil subtidal worm
reef. In the bottom layer you can see planar bedding of quartz sand and shell material,
like what is found if you were to dig a trench on the beach (see the image of a beach
trench on the next page.
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Florida Beach Environment: Generally composed of quartz sand or carbonate sand
with various amounts of shell material depending on the zone of the beach.
Zones of the Beach
Trench on the Beach in the Foreshore Zone, notice the alternating horizontal layers of
shell and sand. This is known as planar bedding.
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Fossil Worm Reef: Some types of subtidal (below the tidal range, always under water)
worms make their homes by burrowing into sand and shell material. When the
material hardens (lithifies) into a rock it becomes a trace fossil.
Present day subtidal worm reef.
Fossil subtidal worm reef dated to be about 120,000 years old.
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Fossil Coral: Corals are made of calcium carbonate. Calcium carbonate dissolves in
acid. Coral material will react (bubble or effervesce) vigorously with application
of hydrochloric acid.
The images above are present day live corals. The image on the left is a coral reef with
various types of corals. The image on the right is a star coral.
The images above are fossilized corals. The image on the left is a fossilized coral reef
dated to be about 120,000 years old. The image on the right is a fossilized star coral.
Sediment: Sediment consists of materials like soil, sand, and minerals that settle to the
bottom of surface water. They are produced by the air or water erosion of land.
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Sediment Characteristics
Wentworth scale: The Wentworth scale is used to describe the size of particles found
in sediments. Cobbles are particles larger than 64 mm in diameter. Smaller types
of particles are pebbles, granules, sand, and silt. Very small particles, those less
than 0.0004 mm in diameter are clay. There are other scales that are used to
describe the size of particles in sediments, but the Wentworth scale is the one
used most often by geologists.
Roundness: The degree of roundness is generally a function of how long the grains
have been moved around. The rounder (less angular) the grains are the longer
the grains have moved around and had time to weather. Also, the more sphere
(less ellipsoidal or egg shaped) like the grains are the longer the grains have
been moved around and eroded through weathering.
Color: Sediments are also classified by their color and how light or dark they are. The
color of particles can provide clues as to what materials the sediments are made
and their location. For example, when shells or coral break up into small particles
they can form the pure white sand found at some beaches.
Grain Sorting: The sorting of a sediment is basically whether it has particles of the
same size or a mixture of different sized particles. The sorting depends on the
distance the sediment was transported and how well it was transported.
Sediments that have been transported by the wind tend to be the most uniform,
but wind only transports smaller particles. Water can transport particles of many
sized, those sediments may have many different sizes.
Types of Sediments Based on Origin:
Lithogenous: “Litho” refers to rock and “genous” to origins. Therefore,
lithogenous sediments come from land and do not contain organic
materials.
Biogenous: Similarly, biogenous sediments come from biological sources and
are made up of organic materials.
Hydrogenous: Sediments that come from the precipitation of minerals in water.
Cosmogenous: Sediments that come from space.
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Name: Answer Key
Date:
Sample
Number
Sample
Collected
From
Color
Size
(mm)
Wentworth
Classification
Texture
(Roundness)
Sand
Subangular
to rounded
Moderately
to well
sorted
Sorting
Composition
(Calcium
carbonate,
silica, or both)
Both (Silica
Grains with
calcium
carbonate shell
material)
Both (Silica
Grains with
calcium
carbonate shell
material)
Shell
Material
Depositional
Environment
Yes
(abundant)
Beach
Yes
(abundant)
Beach (Dune)
Calcium
carbonate
Yes (some)
Beach
Beach (High
energy swash)
1
Sediment
Ft. Pierce,
East Coast of
Florida,
Central FL
Tan
~0.2 to 5
mm,
mostly
0.5 mm
2
Sediment
Ft. Pierce,
East Coast of
Florida,
Central FL
Tan
0.25 to
0.5 mm
Sand
Rounded to
Well
Rounded
Well Sorted
3
Sediment
Florida Keys
Gray and
white
~0.1 to 2
mm
Sand
Subangular
to rounded
Well sorted
4
Sediment
Florida Keys
Various
colors,
mostly white
with reds
and grays
~0.2 to
20 mm,
mostly
about 5
mm
Pebbles
(gravel)
Subangular
to rounded
Poorly
sorted
Calcium
carbonate
Yes
(moderate)
abundant
coral
fragments
5
Sediment
Pensacola,
West Coast of
Florida,
Panhandle FL
Gray-white
0.25 to 1
mm
Sand
Subangular
to rounded
Well sorted
Silica (Quartz)
No
Beach
6
Sediment
Ft. De Soto,
West Coast of
Florida,
Central FL
Gray-white
with little
black
specks
~0.1 to 1
mm,
mostly
~0.25
mm
Well sorted
Both (Silica
Grains with
calcium
carbonate shell
material)
Yes (little)
Beach
Sand
Well rounded
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Name: Answer Key
Date:
Sample
Collected
From
Color
Size
(mm)
Wentworth
Classification
Texture
(Roundness)
Sorting
7
Rock
Florida Keys
White
NA
NA
NA
NA
8
Rock
South
Hutchinson,
East Coast of
Florida,
South FL
NA
Sample
Number
Tan to
orangish tan
NA
NA
NA
Composition
(Calcium
carbonate,
silica, or both)
Shell
Material
Depositional
Environment
Calcium
carbonate
No
Fossil Coral
Reef
Calcium
carbonate (has
some silica but
cannot really
tell)
Yes
(abundant)
Beachrock (you
can even see
the layers of
shell material)
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