University of South Florida



Geology Unit Lab ActivityTeacher PacketIntroduction: 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:Metric RulerMagnifying LensDilute Hydrochloric AcidPetri Dishes for SamplesSamples for AnalysisSediment Samples from East Coast of FloridaSediment Samples from Florida KeysSediment Samples from West Coast of FloridaCoral SampleBeachrock SampleLab HandoutLab 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 2Station 3 and 4: Sediment samples from the Florida Keys, Samples 3 and 4Station 5 and 6: Sediment samples from the west coast of Florida, Samples 5 and 6Station 7 and 8: Rock sample from the Florida Keys, Sample 7Station 9 and 10: Rock sample from the east coast of Florida, Sample 8One 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.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.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 BeachTrench on the Beach in the Foreshore Zone, notice the alternating horizontal layers of shell and sand. This is known as planar bedding. 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.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.Sediment CharacteristicsWentworth 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.3810-1212850Name: Answer Key00Name: Answer Key8255-829310Date: 00Date: Sample NumberSample Collected FromColorSize (mm)Wentworth ClassificationTexture (Roundness)SortingComposition (Calcium carbonate, silica, or both)Shell MaterialDepositional Environment1SedimentFt. Pierce,East Coast of Florida, Central FLTan~0.2 to 5 mm, mostly 0.5 mmSandSubangular to roundedModerately to well sortedBoth (Silica Grains with calcium carbonate shell material)Yes (abundant)Beach2SedimentFt. Pierce,East Coast of Florida, Central FLTan0.25 to 0.5 mmSandRounded to Well RoundedWell SortedBoth (Silica Grains with calcium carbonate shell material)Yes (abundant)Beach (Dune)3SedimentFlorida KeysGray and white~0.1 to 2 mmSandSubangular to roundedWell sortedCalcium carbonateYes (some)Beach4SedimentFlorida KeysVarious colors, mostly white with reds and grays~0.2 to 20 mm, mostly about 5 mmPebbles (gravel)Subangular to roundedPoorly sortedCalcium carbonateYes (moderate) abundant coral fragmentsBeach (High energy swash)5SedimentPensacola, West Coast of Florida, Panhandle FLGray-white0.25 to 1 mmSandSubangular to roundedWell sortedSilica (Quartz)NoBeach6SedimentFt. De Soto, West Coast of Florida, Central FLGray-white with little black specks~0.1 to 1 mm, mostly ~0.25 mmSandWell roundedWell sortedBoth (Silica Grains with calcium carbonate shell material)Yes (little)Beach52070-895350Date: 00Date: 47625-1278890Name: Answer Key00Name: Answer KeySample NumberSample Collected FromColorSize (mm)Wentworth ClassificationTexture (Roundness)SortingComposition (Calcium carbonate, silica, or both)Shell MaterialDepositional Environment7RockSouth Hutchinson, East Coast of Florida, South FLTan to orangish tanNANANANACalcium carbonate (has some silica but cannot really tell)Yes (abundant)Beachrock (you can even see the layers of shell material)8“Unknown” RockFlorida KeysWhiteNANANANACalcium carbonateNoFossil Coral ReefBelow is a map of the state of Florida; label each of the collection sites and which sample #’s were collected at each site. 285750025336500Look at the locations of each of the sediments, how do they differ based on the region, which they were collected?What factors besides location contribute to the differences in these sediment samples?Input data for “Unknown Sample #8” into your chart, based on your data, which region do you infer this sample came from? Be sure to provide three pieces of evidence to support your pare what you found for the location and characteristics of the unknown sample with another group, Are they the same or different, explain?Do you think you need to revise your original conclusion about the unknown, why? ................
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