B-Lab Report 02 Florida 1 - All Versions
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School
University of South Florida *
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Course
2000
Subject
Geology
Date
Feb 20, 2024
Type
Pages
8
Uploaded by BaronArtGrouse30
Report 2-1
Activity 2.1, The Landscape of Florida (11 Minutes)
O
BJECTIVE
:
To learn how the general shape of the landscape and sea floor can be read from the state topographic map.
This activity uses the State of Florida 1:750,000-scale topographic map. 1.
Based on the density of topographic contour lines, what is the hilliest part of Florida? The flattest? (2 points, ☆
) Hilliest: Flattest: 2.
The highest point in Florida is located Walton County, in the western Panhandle. Can you locate it? What is the highest elevation in Florida that can be determined from this map? (2 points, ☆
) Notice that this topographic map also indicates the shape of the land under the sea, as bathymetric
contours and color-coding. The deepest areas are colored dark blue, and the shallowest areas are pale blue. Note also (for reasons that aren’t clear) the bathymetric contours are in meters
while the elevation contours are in feet
! This is a good example why geologists need to be able to convert between units. 3.
To a geologist, ‘Florida’ includes all the continental crust that juts into the Caribbean Sea, including the portion that is submerged beneath shallow waters. The submerged portion of the continents is called the
continental shelf
and is arbitrarily defined as the portion of the ocean shallower than 200 meters. Using this definition, locate the boundaries of the geologists’ Florida, extending from edge of the Atlantic continental shelf in the east to the edge of the Gulf of Mexico continental shelf in the west. Measure this distance on the map with a ruler
–
how many inches is it? (2 points, ☆
) Distance in inches: 4.
Now use the map scale
to convert this map distance to the actual width of the Florida platform, in kilometers (km). Show all your work to get full credit. (3 points, ☆
) 5.
During the peak of the last glaciation, approximately 15,000 years ago, so much of Earth’s water was tied up in glacial ice that sea level was about 330 feet (100 meters) lower than it is today! How far away from Tampa was the western coast of Florida at that time? Give your answer in kilometers. Again, use the map scale and show your work below. (2 points, ☆
) Activity 2.2, Topographic Contours (3 Minutes)
O
BJECTIVE
:
To review the meaning of topographic contour lines.
This warm-up exercise reinforces what you learned in your introductory laboratory about topographic maps. It uses the Lee, FL 7.5-minute topographic quadrangle. The Figure 2.1 is an enlargement of the topographic map in the vicinity of Lee, Florida. Now, suppose that the town of Lee wants to put in a paved path leading from the Junior High School to Stonewall Cemetery, where a popular teacher, tragically killed in a shop accident, is buried. Also assume that the path must be perfectly flat since many students are recuperating in wheelchairs due to the same freak accident. Trace the path on Figure 2.1 that leads from the Jr. High School to the cemetery and that is as flat as possible. (3 points, ☆
) Laboratory Number Two: Florida, The Land Beneath Our Feet I Name: Partners:
Report 2-2 Figure 2-1: Topographic Map for Activity 2.2 Activity 2.3, Eloise, FL Quadrangle (9 Minutes) O
BJECTIVE
:
To review how to read elevations off a topographic map.
This is a warm-up exercise designed to make sure you know how to read elevations on a topographic map. Determine the elevations of the following lakes. (3 points each, ☆
) Lake Elevation (feet) Lake McLeod (W edge of map) Lake Myrtle Flora Lake (S of Lake Garfield) Activity 2.4, Gap Lake and Goulds Quadrangles (FL) (
4 Minutes)
O
BJECTIVE
:
To review the concept of contour interval on topographic maps.
The Gap Lake and Goulds, FL quadrangles show the range of topography observed in Florida. Answer the following questions, which explore the relationship between hilliness and contours. 1.
What is the contour interval for these quadrangle maps? (1 2.
Why do you think the mapmakers decided to use a different contour interval for these two maps? (2 points, ☆☆)
?
Activity 2.5, Brooksville SE, FL Quadrangle (7 Minutes)
O
BJECTIVE
:
To learn how to construct a topographic profile from a topographic map.
On the graph on page Report 2-3, construct a topographic profile of an area in the southwest corner of this quadrangle, just to the north and east of Irvin Lake. The profile line should go in a straight line between the two dots marked on the topographic map
(7 points,
☆
).
Activity 2.6, Brooksville SE, FL Quadrangle (8 Minutes)
O
BJECTIVE
:
To learn how to construct a fall line path on a topographic map.
The exercise in this section requires you to predict the path of a ball rolling downhill on the landscape of the Brooksville SE quadrangle. Reproduced on page Report 2-4 is an enlarged portion of the topographic map of this quadrangle in the area just north of Mundgen Hill. There are three dots located on the figure labeled A, B, and C. Starting from each dot, draw the fall line by applying the rules described in your laboratory manual. There will be three separate lines. Make sure your lines are easy to see. (8 points
, ☆
) point each, ☆
)
Quadrangle Contour Interval (feet) Gap Lake Goulds
Report 2-3 Graph for constructing topographic profile, Activity 2.5
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Report 2-4 Base map for constructing topographic fall line, Activity 2.6
Report 2-5 Activity 2.7, Florida Minerals (16 Minutes) O
BJECTIVE
:
To learn how to recognize the common minerals of Florida: calcite/aragonite, dolomite, quartz, and gypsum.
NOTE: This activity must be done before any other rock or mineral activities in the laboratory. Box 1 contains large single crystal specimens of the four minerals that are abundant in Florida: calcite, dolomite, quartz,
and gypsum
. Gypsum is sometimes replaced by the mineral anhydrite
, which has the same chemical formula as gypsum except it lacks chemically bonded water, and it has similar, but not identical, physical properties. 1.
Examine the specimens carefully and fill in the following table which summarizes their physical properties. (3 points each, all ☆
)
Cleavage? Hardness? Luster? Fizz with HCl? F-A1: Dolomite F-A2: Calcite F-A3, F-A5: Quartz F-A4: Gypsum 2.
In the table you just completed, underline the properties that you think will be most useful in identifying each mineral in hand sample. (1 point each, all ☆
)
Activity 2.8, Introduction to Florida Rocks (12 Minutes)
O
BJECTIVE
:
To learn how to recognize the important rock types found in Florida: limestone, dolostone, chert, nodular anhydrite, and limey siltstone/mudstone. Most of the rocks underlying Florida are not exposed on the surface in outcrops and can only be examined in cores
–
samples of material collected by drilling into the earth. In this activity, you will see representative samples of the rocks that make up Florida. Most of the samples are cut from 2-inch or 4-inch cores and are fragile
–
be careful with them (they are truly irreplaceable in many cases). 1.
Sample FLA-1 is a limestone from Charlotte County. What mineral makes up nearly 100% of this limestone? (1 point, ☆
) 2.
How can you easily identify limestones in this laboratory? (1 point, ☆
) 3.
Sample FLA-2 is a dolostone from Charlotte County . What mineral makes up nearly 100% of this dolostone? (1 point, ☆
) 4.
How can you easily identify dolostones in this laboratory? (1 point, ☆
) 5.
Sample FLA-3 is a sample of nodular anhydrite from Charlotte County. Describe the appearance of the polished surface on the nodular anhydrite. (2 points, ☆☆
) 6.
Sample FLA-4 is a sample of chert from the Tampa Limestone, collected on Caladesi Island, Pinellas County. It was collected from near the surface, so it isn’t a core.
What mineral makes up chert? (1 point, ☆
) 7.
List at least two properties of chert that allow it to be identified in this laboratory. (2 points, ☆☆
) 8.
Sample FLA-5 is a limey siltstone/mudstone. It is one of the most complicated rocks you will see in this laboratory and defies easy classification because it contains both quartz
–
a terrigenous clast
–
and calcite,
aragonite, or
Report 2-6 dolomite
–
chemical precipitates. Depending on the amount
of quartz versus carbonate material, these rocks will be classified either as limey siltstones/mudstones, or silty limestones! The little black specks in this rock are phosphate minerals
, and they are usually very abundant in rocks of this type. Use the inside back cover of your lab manual to estimate the percentage of phosphate in FLA-5. (2 points, ☆
) 9.
Is there any calcite or dolomite in this rock? How can you tell? (1 point, ☆☆
) Activity 2.9, Summary of Florida Rocks (16 Minutes)
O
BJECTIVE
:
To summarize the types and abundances of rocks and sediments found in Florida, as a function of depth and age.
Table II-1 summarizes the rocks found beneath Florida to a depth of approximately 3 km, including the location, depth and age, and group or formation of each core. Note that K/J means “Cretaceous/Jurassic”.). Notice that the rows in the table are arranged in terms of increasing age. For each rock sample, identify the kind of rock. (2 points each, all ☆
). Activity 2.10, Florida Minerals in Thin Section: Quartz (
5 Minutes
) O
BJECTIVES
:
(a) To learn how to recognize quartz in thin section; (b) to review the meaning of the principal terms used to describe the optical properties of minerals in thin section: opaque, isotropic, anisotropic, birefringence. The thin section for this activity (labeled Activity 2-10) is of a sandstone composed entirely of quartz
. This sandstone isn’t from Florida, but it was chosen because in this rock it is easy to see the distinctive optical properties of quartz. In most Florida rocks, quartz occurs as tiny fragments mixed with other minerals, principally calcite/aragonite and dolomite. Put check marks in the following table to summarize the optical properties of quartz: (5 points, ☆
) Cleavage visible? Pick one! Opaque? Isotropic? Anisotropic? Birefringence, if Anisotropic Grays Vivid Washed-out Table II-1, Representative Rocks and Sediments of Florida Sample Rock or Sediment? County Depth (feet) Age Group or Formation Name of Rock? Youngest
. FLA-6 Rock Dade 40 Pliocene Miami Fm. FLA-7 Rock Manatee 343 Miocene Arcadia Fm. FLA-5 Rock Clay? ≈ 250
Miocene Hawthorn Grp. Siltstone
FLA-8 Rock Hardee? ≈ 100
Miocene Hawthorn Grp. FLA-9 Rock Manatee 920 Eocene Ocala Grp. FLA-10 Rock Lafayette 300 Eocene Avon Park Fm. FLA-11 Rock Citrus 35 Eocene Ocala Grp. FLA-2 Rock Citrus 280 Eocene Avon Park Fm. Dolostone
FLA-1 Rock Charlotte 1180 Eocene Avon Park Fm. Limestone
FLA-12 Rock Escambia 15847 K/J Unknown Oldest FLA-13 Rock Charlotte >10,000 K/J Unknown FLA-3 Rock Charlotte? >15,000 Jurassic Unknown Nodular Anhydrite
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Report 2-7 Activity 2.11, Florida Minerals in Thin Section: Calcite and Dolomite (
5 Minutes
) O
BJECTIVES
:
(a) To learn how to recognize calcite or dolomite in thin section; (b) to review the meaning of the principal terms used to describe the optical properties of minerals in thin section: opaque, isotropic, anisotropic, birefringence.
The thin section for this activity (labeled Activity 2-11) is of a marble composed entirely of calcite
. This marble isn’t from Florida either, because almost all the calcite contained in Florida rocks is fine-grained, and marble doesn’t occur at all. Nonetheless, this marble displays the distinctive optical properties of calcite (or dolomite) beautifully. Calcite and dolomite cannot be distinguished in thin-section
–
but are easy to distinguish from other minerals because they are the only common minerals that exhibit washed-out birefringence
. Put check marks on the following table to summarize the other optical properties of calcite: (3 points, ☆
) Cleavage visible? Pick one! Opaque? Isotropic? Anisotropic? Birefringence, if Anisotropic Grays Vivid Washed-out EXTRA CREDIT, Florida Minerals in Thin Section: Gypsum and Anhydrite O
BJECTIVES
:
(a) To learn how to recognize gypsum and anhydrite in thin section; (b) to review the meaning of the principal terms used to describe the optical properties of minerals in thin section: opaque, isotropic, anisotropic, birefringence.
The thin section for this activity (PS9-4) is from a rock recovered from nearly 3 miles below the surface of Florida. It contains the evaporite minerals gypsum
and anhydrite
. Both of these minerals are relatively rare, but they are important in rocks that underlie the thick limestones under Florida. Both gypsum and anhydrite are anisotropic
but can be easily distinguished from each other based on their birefringence: anhydrite has vivid birefringence and gypsum has gray birefringence. Which mineral, gypsum or anhydrite is more abundant in this rock? (3 points, ☆
) Activity 2.12, Florida Rocks in Thin Section (
7 Minutes
) O
BJECTIVES
: (a) To learn how to recognize limestone in thin section; (b) to learn how to recognize silty limestone in thin section. 1.
The thin section (FLA-14) is of rock FLA-14, a piece of the important Avon Park Formation. You will notice that the
crystals in this rock are much, much smaller than the rocks you’ve seen before. Nonetheless, if you look at them carefully (and perhaps with the aid of high magnification) you can determine what they are. What mineral is FLA-14 composed of? (3 points, ☆
) 2.
The thin section (FLA-5) is of rock FLA-5, a piece of the Hawthorn Group. This is the most complicated rock you will see in this laboratory, partly because the rock is fine-grained and partly because it contains more than one mineral. Notice the black specks on this rock that can be seen in the hand sample
–
these are phosphate minerals, principally the mineral apatite
. In thin section, these phosphate minerals appear opaque. FLA-5 also contains abundant calcite and dolomite, which appear brown in thin section. The calcite and dolomite crystals are very small, and it is difficult, if not impossible, to notice the distinctive birefringence of calcite/dolomite. Nonetheless, you should be able to determine that the dusty brown material in plain-polarized light is indeed isotropic when you view it under cross-polarized light. What other mineral in addition to calcite/dolomite and phosphate can you see in FLA-5? (4 points, ☆
) Activity 2.13, Using a Sediment Card (
5 Minutes
) O
BJECTIVES
: (a) To learn how to recognize the different sizes of sand and silt; (b) to learn how to determine roundness of clasts; (c) to learn how to recognize quartz clasts.
During this activity you will use a sediment card
–
a reference tool to identify the principal sizes of sediment visible to the naked eye. In lieu of using loose sediment, these sediment cards use sandpaper to represent the range of clast sizes found in sandstones, siltstones, and mudstones. 1.
There is a wooden block that contains sediment trapped between pieces of clear tape, which you can examine with a hand lens. By comparing these trapped sediments to the sediment card, determine the clast size of each sediment and enter it into the second column of the table below. (1 point each, all ☆
):
Sediment Clast Size Clast Roundness A B C
Report 2-8 2.
Now using a hand lens, determine the roundness of the clasts for sediment A and B and enter it into the third column of the table you just used. (1 point each, all ☆
). 3.
What mineral are the clasts in sediment A made of? How can you tell? (3 points, ☆☆
) 4.
Finally, use the sediment card to determine the principal clast size in each of the following rocks: (2 points each, all ☆
) Rock Principal clast size F-E1 F-E2