ESC1000C_Rocks_LabExploration_AnswerTemplate_Summer2023_v1 (1) (1)
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Florida SouthWestern State College, Fort Myers *
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1000C
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Geology
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Feb 20, 2024
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Florida SouthWestern College
Introduction to Earth Science
Exercise 3: Rocks Answer Template
Directions:
Although you can work together as a group, each individual student should compose their own well-conceived and articulate answers on the RockLab_AnswerTemplate.docx (see Rock Exploration Activity page). Please submit
the .docx AnswerTemplate to the Rock Exploration Assignment page. Alert me by email if you have any questions or issues accessing the files. The answer form below works best in MS Word which is freely available via FSW’s Office 365, please click and then type in areas designated (“
Click or tap here to enter text”). Igneous Rock Questions 1.
Answer the questions based on the texture quality of the igneous rocks only
.
a)
The igneous rocks that have fine-grained textures are basalt, rhyolite, and andesite.
b)
The igneous rocks that have coarse grained textures are granite, diorite, and
gabbro.
c)
The igneous rock that has glassy texture is obsidian.
d)
A felsic composition is a compositional group of igneous rocks that indicates a rock is composed almost entirely of light-colored silicates. Two examples are granite and rhyolite. A mafic composition is a compositional group of igneous rocks indicating that the rock contains substantial dark silicate minerals and calcium-itch plagioclase feldspar. Two examples are gabbro and basalt.
e)
(Complete sentences) Only small to microscopic crystals grow during rapid cooling farther away from the magma chamber, as indicated by the fine-
grained texture. Large crystals form when magma cools slowly, allowing for an extended period of crystal formation, indicated by the coarse-grained texture.
2.
Locate on the diagram below where you would expect each of the igneous rocks listed above to form considering whether on average they are intrusive (cool slowly), extrusive (cool quickly), or cool instantaneously. Indicate on your worksheet where all the igneous would likely form (A, B, or C).
a)
Granite, Diorite, Gabbro
b)
Rhyolite, Basalt, Andesite
c) Obsidian
Continue to the next page…
3.
Classify (type of texture and felsic/mafic) and identify (general name (ex. “granite”) both of the igneous
rocks in the picture series below. Provide the reasons for how you know… (Example: “Felsic intrusive igneous rock, possibly a granite based on …”)
a. Mafic intrusive igneous rock, possibly a diorite based on dark-colored minerals and visible grain.
b. Felsic intrusive igneous rock, possibly rhyolite, based on the fine-grained and light-colored texture.
Sedimentary Rock Questions – use the Rocks_LabExploration.pdf for rock images (slides 6-11)
4.
By what characteristic are detrital sedimentary rocks classified? What are the specific classification categories?
Detrital sedimentary rocks are classified based on their particle size. The specific classification categories are:
Pebble, cobble, boulder, and granule-sized particles are larger than 2 millimeters.
Sand particles are between 1/16 and 2 millimeters.
Clay particles are less than 1/256 millimeters. Silt-sized particles are between 1/256 and 1/16 millimeters.
5.
Arrange the following 5 steps (Transport, Deposit, Cement, Weather, Compression) in the correct sequence starting from an exposed, pre-existing rock to the formation a detrital sedimentary rock. Weather Transport Deposit Compression Cement 6.
Answer the questions below based on the sedimentary rocks found in the rock image .pdf
a)
Sandstone is an abundant, durable detrital sedimentary rock primarily composed of sand-size grains. The individual grains in sandstone are often rounded or sub-angular. Conglomerate is a sedimentary rock composed of large, course, rounded, gravel-size particles.
b)
Heavy particles, like gravel, larger than 2 millimeters, remain at the bottom of a high-energy water environment. These kinds of particles are frequently found in conglomerates in sedimentary rocks.
7.
Answer the two questions below:
a)
The individual particles are broken into smaller and smaller pieces, each retaining the characteristics of the original material. The end result is many small rounder pieces from a single large one
.
b)
Sedimentary rock samples such as sandstone, shale and limestone are composed of individual rock particles that exhibit this long-timespan transport.
8.
Once deposited, how are the individual particles in a detrital sedimentary rock put together to make a new rock?
Lithification is the process, generally cementation and/or compaction, of converting sediments to solid rock. As sediments accumulate through time, the weight of overlying material compresses the deeper sediments. As the grains are pressed closer and closer, pore space is greatly reduced.
9.
Metamorphic Rock Questions
– (slides 12-18) Contact Metamorphism -
When rock is intruded by magma, the magma heats the adjacent rock to temperatures that cause metamorphic changes.
Regional Metamorphism - During Mountain building, great quantities of rock are subjected to pressures and high temperatures associated with large-scale deformation.
a.
Low-grade Metamorphism:
. Slate
. Anthracite Coal
High-grade Metamorphism:
. Gneiss
. Schist
. Marble
. Quartzite
High-grade metamorphism is clearly indicated by the banding. The separation of light and dark minerals into separate bands gives gneiss rocks their banded appearance.
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