MIDTERM 2 Review

Question 1

Igneous rocks

What are granitic and basaltic rocks?
How do we differentiate them?

Answer 1

Granitic rocks are FELSIC while basaltic rocks are MAFIC.
Felsic rocks contain lighter coloured minerals while MAFIC rocks contain darker colored minerals.

Question 2

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

Answer 2

It is an ultramafic rock that would occur in th earth’s mantle.

Question 3

Igneous rocks

What is the dominant mineral in Felsic rocks?

Answer 3

Quartz and K-feldspar

Question 4

Igneous rocks

What controls the texture of igneous rocks?
What does a porphyritic texture tell us?

Rock with two different crystal sizes.

Answer 4

The rate of cooling controls the texture of igneous rocks.
A porphrytic texture tells us that large crystals formed while the magma was cooling

Question 5

Igneous rocks

Compare and contrast the processes that result in VESICULAR and AMYGDALOIDAL texture.

Answer 5

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.

Question 6

Igneous rocks

What features do rhyolite and basalt share?
How do they differ?

Answer 6

They are both fine-grained rocks but basalt is a mafic rock and rhyolite is a felsic rock.

Question 6

Igneous Rocks

Compare and contrast batholiths and stocks.

Answer 6

Both are almost always felsic or intermediate rock types that form along convergent boundaries but batholiths are larger than stocks.

Question 7

Igneous Rocks

Compare and contrast dikes and sills

Answer 7

Both are igneous intrusions but DIKES cut across existing rocks while SILLS don’t

Question 8

Weathering

What is the difference between weathering, erosion, and transport?

Answer 8

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

Question 9

Weathering

Under what conditions does deposition occur?

Answer 9

When the carrying medium (water or air) of sediment slows down allowing grains to settle temporarily or permanently.

Question 10

Weathering

Describe as many mechanical weathering processes as you can.

Answer 10

• Frost wedging
• Pressure release
• Crystal growth

Question 11

Weathering

Describe as many chemical weathering processes as you can.

Answer 11

• Dissolution
• Hydrolysis
• Oxidation

Question 12

Weathering

Which rock is more easily weathered? Granite or Basalt? Why?

Answer 12

Basalt weathers more easily because its minerals are more unstable to weathering.

Question 13

Weathering

How does climate affect weathering?

Answer 13

Chemical weathering is accelerated by hot and wet climate while physical weathering is accelerated by cold dry climates.

Question 14

Weathering

What two processes control lithifcation and how do they operate?

Answer 14

Compaction packs sediment through burial and reduces volume by 40%
Cementation is the precipitation of minerals from sediment pore fluids to bind grain together.

Question 15

Sedimentary rocks

Why is quartz the most commin mineral in sed. rocks?

Answer 15

Quartz is the most resistant to weathering processes

Question 16

Sedimentary rocks

How can you tell the different between SHALE, MUDSTONE, and SILTSTONE?

Answer 16

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

Question 17

Sed. Rocks

What does roundness and particle size tell us about sed. rocks?

Answer 17

Roundness and particle size tells us how far sediment travelled (the farther the rounded and finer grained)

Question 18

Sed. Rocks

How do you determine if a rock came from a high or low energy environment? Give some examples.

Answer 18

• Grain size/ roundness of grain
• How sorted the grains are

Question 19

Metamorphic rocks

Foliated vs Non-foliated rocks. Why are they different?

Define them and explain why they are different.

Answer 19

Foliated rocks have nearly flat arrangements of mineral grains. (Gneiss rock) while non-foliated rocks don’t have visible layers.

Question 20

Metamorphic rocks

In what metamorphic environment does greenschist and zeolite facies occur in?
* Subduction
* Regional
* Contact
* Hydrothermal

Answer 20

Regional metamorphism

Question 21

Geologic Time

Identify and explain the seven prinicples of dating sed.rocks

Answer 21

• 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.

Question 22

Geologic Time

What is the difference between angular unconformities, disconformities, and nonconformities.

Answer 22

• 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

Question 23

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.

Answer 23

The rock mass adjacent to the one with inclusions was there first.

Question 24

Geologic Time

Why is a fossile assemblage more useful than a single fossil to date a sed.rock layer?

Answer 24

A fossil assemblage can tell scientists which geologic period a rock existed in because they are unique to their time period.

Question 25

Geologic Time

What is an isotopic half-life? How is it used to calculate numerical ages?

Answer 25

• 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.