Lesson 5 assignement
pdf
keyboard_arrow_up
School
Johns Hopkins University *
*We aren’t endorsed by this school
Course
101
Subject
Geology
Date
Apr 3, 2024
Type
Pages
2
Uploaded by bartman2381
Geology 101
—
Lesson 5 Assignment
1.
What is foliation? What causes it? Foliation is a type of common texture in Metamorphic rocks often exhibit. Foliation is the parallel alignment of mineral grains within the rock which is caused by differential stress and pressure during the rock's formation. This pressure and stress result in the reorientation of mineral grains, creating a layered or banded appearance in the rock. For example, when shale is subjected to heat and pressure, it transforms into slate, and the alignment of clay minerals within the rock gives rise to foliation. 2.
Distinguish between slaty cleavage and schistosity. Slaty cleavage -
Slaty cleavage refers to the parallel alignment of fine-grained minerals, such as clay minerals, within the rock, resulting in a smooth, planar structure -
Finer mineral grains -
the rock appears smooth and can be split into thin, flat sheets Schistosity -
schistosity involves the separation of minerals into distinct layers, often with visible mica grains, giving the rock a banded appearance. -
Coarser grain -
Scaly appearance 3.
How might you visually distinguish between samples of phyllite and schist? Phyllite has a somewhat shiny or satiny sheen due to the very fine-grained mica flakes, while schist has a more distinctly flaky or scaly appearance due to the coarser mica crystals that can often be seen with the naked eye. 4.
How might you distinguish a specimen of marble from one of quartzite? Think of 2 different tests you could apply. 1.
Marble will fizz with hydrochloric acid
2.
Marble is softer and can be easily scratched with a knife
5.
Is shale a metamorphic rock? Explain. No, shale is a sedimentary rock, not a metamorphic rock. It forms from compacted mud and clay particles. When shale is subjected to heat and pressure, it can metamorphose into the foliated metamorphic rocks slate, phyllite, schist, and gneiss. 6.
How is a hand specimen of gneiss distinguished from granite? How is it similar to granite? Gneiss has a banded or foliated appearance due to the segregation of light and dark mineral grains into alternating layers or lenses during high-grade regional metamorphism. Granite lacks this foliated texture. However, the overall mineralogy of gneiss (quartz, feldspar, mica) is similar to granite. 7.
Arch dams in canyons require the canyon walls to be strong and resistant to leakage of reservoir water around the dam. Which metamorphic rock would probably make the best canyon wall foundation for an arch dam such as Hoover Dam? Why? Quartzite would likely make the best canyon wall foundation rock for an arch dam like Hoover Dam. Quartzite is extremely hard, dense, impermeable, and resistant to weathering due to the interlocking quartz crystals created by metamorphism. This makes it strong enough to support the dam's weight and resistant to water leakage. 8.
What is a metamorphic index mineral? A metamorphic index mineral is a mineral that only forms under specific temperature and pressure conditions during metamorphism. The presence of certain index minerals like staurolite, kyanite, sillimanite allows geologists to determine the metamorphic grade or intensity that a rock was subjected to.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help