MIDTERM 2 Review Flashcards
This deck covers igneous rocks, sed. rocks, weathering, metamorphic rocks and geological time.
Igneous rocks
What are granitic and basaltic rocks?
How do we differentiate them?
Granitic rocks are FELSIC while basaltic rocks are MAFIC.
Felsic rocks contain lighter coloured minerals while MAFIC rocks contain darker colored minerals.
Igneous rocks
What type of rock is mostly made of olivine with lesser amounts of pyroxene and calcium rich felspars? Where would it most likely occur?
Look over Lab with igneous rocks
It is an ultramafic rock that would occur in th earth’s mantle.
Igneous rocks
What is the dominant mineral in Felsic rocks?
Quartz and K-feldspar
Igneous rocks
What controls the texture of igneous rocks?
What does a porphyritic texture tell us?
Rock with two different crystal sizes.
The rate of cooling controls the texture of igneous rocks.
A porphrytic texture tells us that large crystals formed while the magma was cooling
Igneous rocks
Compare and contrast the processes that result in VESICULAR and AMYGDALOIDAL texture.
Vesicular rocks are formed when gas bubbles are trapped in the lava. AMYGDALOIDAL rocks form in a similar way but the gas bubbles are filled with secondary minerals.
Igneous rocks
What features do rhyolite and basalt share?
How do they differ?
They are both fine-grained rocks but basalt is a mafic rock and rhyolite is a felsic rock.
Igneous Rocks
Compare and contrast batholiths and stocks.
Both are almost always felsic or intermediate rock types that form along convergent boundaries but batholiths are larger than stocks.
Igneous Rocks
Compare and contrast dikes and sills
Both are igneous intrusions but DIKES cut across existing rocks while SILLS don’t
Weathering
What is the difference between weathering, erosion, and transport?
Weathering is the physical breakdown and chemical alteration of a rock at or near Earth’s surface.
Erosion is the physical removal of material by water, ice, or wind from a previously stationary position.
Transportation is the active movement of sediment in water ice or air
Weathering
Under what conditions does deposition occur?
When the carrying medium (water or air) of sediment slows down allowing grains to settle temporarily or permanently.
Weathering
Describe as many mechanical weathering processes as you can.
- Frost wedging
- Pressure release
- Crystal growth
Weathering
Describe as many chemical weathering processes as you can.
- Dissolution
- Hydrolysis
- Oxidation
Weathering
Which rock is more easily weathered? Granite or Basalt? Why?
Basalt weathers more easily because its minerals are more unstable to weathering.
Weathering
How does climate affect weathering?
Chemical weathering is accelerated by hot and wet climate while physical weathering is accelerated by cold dry climates.
Weathering
What two processes control lithifcation and how do they operate?
Compaction packs sediment through burial and reduces volume by 40%
Cementation is the precipitation of minerals from sediment pore fluids to bind grain together.
Sedimentary rocks
Why is quartz the most commin mineral in sed. rocks?
Quartz is the most resistant to weathering processes
Sedimentary rocks
How can you tell the different between SHALE, MUDSTONE, and SILTSTONE?
SHALE has the ability to split into thin layers
MUDSTONE breaks into chunks or blocks
SILTSTONE has silt- sized particles and contains less clay size material than shale and mudstone
Sed. Rocks
What does roundness and particle size tell us about sed. rocks?
Roundness and particle size tells us how far sediment travelled (the farther the rounded and finer grained)
Sed. Rocks
How do you determine if a rock came from a high or low energy environment? Give some examples.
- Grain size/ roundness of grain
- How sorted the grains are
Metamorphic rocks
Foliated vs Non-foliated rocks. Why are they different?
Define them and explain why they are different.
Foliated rocks have nearly flat arrangements of mineral grains. (Gneiss rock) while non-foliated rocks don’t have visible layers.
Metamorphic rocks
In what metamorphic environment does greenschist and zeolite facies occur in?
* Subduction
* Regional
* Contact
* Hydrothermal
Regional metamorphism
Geologic Time
Identify and explain the seven prinicples of dating sed.rocks
- Superposition, the youngest rocks are at the top and the oldest rocks are at the bottom
- Original Horizontality, sediment layers are deposited in a horizontal position
- Lateral Coninuity, sediments are deposited over a large area in a continous sheet - usually on the contintenal shelf
- Crosscutting relationships, geologic features that cut across rocks must form AFTER those rocks
- ** Inclusions**, Rock mass adjacent to the one with inclusions had to be there first to provide the inclusions
- Uncomformities, are missing part/ gaps of rock records. Angular, tilted or folded sed. rocks overlain by more flat-lying strata. Disconformity, a gap that represents a period of non-deposition and erosion of sed.rocks. Non-conformity, a gap that represents a priod of erosion that exposed deep rocks at the surface.
Geologic Time
What is the difference between angular unconformities, disconformities, and nonconformities.
- Angular unconformities are tilted/folded sed, rocks overlain by more flat lying strata
- A disconformity is a gap that represents a period of non-deposition and erosion of sed.rocks
- A nonconformity is a gap that represents a period of uplift and erosion that exposed the deep rocks at the surface
Geologic Time
What do xenoliths in an igneous intrusion indicate? How do you identify them?
A xenolith is a foreign piece of rock trapped in another rock.
The rock mass adjacent to the one with inclusions was there first.
Geologic Time
Why is a fossile assemblage more useful than a single fossil to date a sed.rock layer?
A fossil assemblage can tell scientists which geologic period a rock existed in because they are unique to their time period.
Geologic Time
What is an isotopic half-life? How is it used to calculate numerical ages?
- Isotopic half-life is the time required for half the nuclei in a sample to decay
- We measure the ratio of parent to daughter isotopes.
