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GEOL 101- Adam Beyer- Exam 3
Terms in this set (61)
What is a metamorphic rock?
Rock formed by the alteration of preexisting rock underground.
What causes a parent rock to undergo metamorphism?
Heat, pressure, and/or chemically active fluids
What changes occur between the parent rock and the newly-formed metamorphic rock?
It's mineralogy, texture, and sometimes chemical composition.
Overall, what is the most important agent of metamorphism (drives recrystallization)?
What is recrystallization?
The formation of new mineral grains that tend to be larger than the original grains.
What does the 'metamorphic grade' of a metamorphic rock refer to?
The degree to which a parent rock changes during metamorphism.
What is texture when referring to metamorphic rocks?
Larger crystals and layering, or banded appearance.
What is foliation?
Flat arrangement of mineral grains or crystals.
How/Why does foliation develop in certain metamorphic rocks?
It occurs by folding, driven by compressional stress that shortens rock units.
Why might a rock never be able to develop foliation despite significant metamorphism?
Deformation is minimal and the parent rocks contain crystals.
How does grain size change with increasing foliation/higher metamorphic grade?
The grains become enlongated (flatter)
What is contact metamorphism?
Changes in a rock due to the heat of a nearby magma source.
What is the aureole of contact metamorphism?
A zone of alteration
What are the heat/pressure conditions associated with subduction zones?
High-pressure, low temperature
What are the heat/pressure conditions associated with continental collision?
High-pressure, high temperature
What are the heat/pressure conditions associated with burial metamorphism?
Confining pressure and temperature
What are index minerals and why are they helpful?
A mineral that's good for indicating metamorphic environments. They are used to distinguish different zones of regional metamorphism.
What is a metamorphic facies?
Minerals used to find the pressures and temperatures that rocks undergo metamorphism.
What are the two primary types of weathering?
Mechanical and Chemical
How do mechanical and chemical weathering work simultaneously and reinforce one another?
Mechanical weathering increases surface area available to be broken down by chemical weathering. Chemical weathering weakens the bonds of rocks aiding mechanical weathering.
What do all of the chemical weathering processes have in common?
Water is the leading role in all chemical weathering.
What climate would be best in order for chemical weathering processes to dominate?
Warm and moist.
What causes differential weathering of rock?
The components surrounding the rock change the type of weathering.
How does soil form?
Weathering and mixing with other materials
What is soil?
A combination of mineral and organic matter, water, and air.
What is regolith?
A layer of rock and mineral fragments.
What is humus?
The decayed remains of animal and plant life.
What are the different controls on soil formation?
Parent Material, Time, Climate, Plants and Animals, and Topography.
Mineral matter with some humus
Little organic matter
Accumulation of clay
Partial Parent Material
Excellent rock cleavage
Most often generated from low-grade metamorphism of shale, mudstone, or siltstone
Degree of metamorphism between slate and schist
Platy minerals are larger than slate but not large enough to see with the unaided eye
Glossy sheen and wavy surfaces
Exhibits rock cleavage
Medium- to coarse-grained
Parent rock is shale that has undergone medium- to high-grade metamorphism
The term schist describes the texture
Platy minerals (mainly micas) predominate
Can also contain porphyroblasts
Medium- to coarse-grained metamorphic rock with a banded appearance
The result of high-grade metamorphism
Composed of light-colored, feldspar-rich layers with bands of dark ferromagnesian minerals
Crystalline rock from limestone or dolostone parent rock
Main mineral is calcite
Calcite is relatively soft (3 on the Mohs scale)
Used as a decorative and monument stone
Impurities in the parent rocks provide a variety of colors
Formed from a parent rock of quartz-rich sandstone
Quartz grains are fused together
Pure quartzite is white
Iron oxide may produce reddish or pink stains
Dark minerals may produce green or gray stains
Parent rock is shale or clay-rich rocks
"Baked" by an intruding magma body
How much of Earth's surface do Sedimentary rocks cover?
Why are sedimentary rocks an important resource?
Coal, fossil fuels, drinking water or ores
What are the steps in the formation of Sedimentary rocks?
Weathering, Transportation, Deposition, Lithification.
What are detrital sedimentary rocks?
Rocks that form from the accumulation of materials that originate and are transported as solid particles.
What are common detrial sedimentary rocks?
What is sorting?
The degree of similarity in particle size in sediment or sedimentary rocks.
What is rounding?
The constant collision of rocks with other surfaces that smoothes out its edges.
What are chemical sedimentary rocks?
A rock that forms when mineral constituents in solution become supersaturated and inorganically precipitate.
What is diagenesis?
Changing sedimentary rocks into different sedimentary rocks at temperatures lower than needed to make metamorphic rock.
What is lithification?
Sediments compact under pressure and become solid rock.
Different environments for deposition of sediment?
Marine, Continental, and Transition
Metamorphism involves the transformation of pre-existing rocks by _____.
Heat and pressure
What is the definition of a parent rock?
The rock that was altered by metamorphism
Which of the following lists of metamorphic rocks places the rocks in order from lowest metamorphic grade to highest?
Slate, Phyllite, Schist, Gneiss
True or False? Metamorphism ends when the rock begins to melt.
Which of the following best describes the difference between differential stress and confining pressure?
In differential stress, the stresses on the sides are greater than the force of gravity. Stresses are the same on all sides for confining pressure.
Which of the following describes the orientation of the long axes of rocks and mineral grains in relationship to the stress applied? Choose all that apply.
The long axis of a rock is parallel to the direction of the weakest stress applied
Mineral grains are oriented parallel to the direction of the weakest stress applied.
What is the most efficient agent of metamorphism?
Contact metamorphism takes place when rocks _____.
Come in contact with a magma body
In addition to temperature, which of the following agents increases with depth in Earth?
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