GEOL EXAM FINAL

Divergent boundary

Plates move apart; form new crust - mid ocean ridges

Convergent boundary

Plates move together; subduction or collision occurs

Transform boundary

Plates slide past each other; cause earthquakes and fault lines.

Continent- collision

Two continental plates collide and build mts

What causes seasons?

Earths tilt, as Earth orbits the sun, changing sunlight angle and day length

What is Earth’s geothermal gradient

Temperature increases with depth, about 25-30 degrees C per km in the crust

Difference between oceanic and continental crust, and how it relates to subduction and plate tectonics? In a subduction zone, which type of crust is subducted, and why?

Oceanic crust is thinner, denser, basaltic;

Continental crust is thicker, less dense, granitic

Oceanic crust subduct because it is denser

What minerals would you expect to find in oceanic crust versus continental crust

Oceanic: olivine, pyroxene, plagioclase

Continental: quartz, feldspar, mica

What does the words lithosphere refer to?

The rigid outer layer of Earth (crust + uppermost mantle)

What is a polymorph

Minerals with the same chemical composition but different crystalline structure

What are the 5 criteria that define a mineral?

Naturally occurring

Inorganic

Solid

Def chemical composition

Orderly crystal structure

What is Bowens reaction series

The sequence minerals crystallize from cooling magma

What does mineral hardness refer to

Resistance to scratching

With regard to minerals, what is the difference between cleavage and fracture

Cleavage = breaks along flat planes

Fracture = irregular breakage

Along what type of tectonic boundary would you find arcs

Ocean convergent boundaries

How fast is earth spinning at the equator? How does that change as you move north/south

About 1670 km/hr (1040 mph) at the equator; slower toward the poles

The Appalachians are an old version of what type of plate boundary

Continent convergent boundary

How fast approx do Earths tectonic plates move

Cm/year - about as fast as fingernails grow

The Pacific Ring of Fire is a consequence of what type of plate boundary

Convergent/subduction boundaries

What type of rock is the mantle made of?

Periodtite

What is magma?

Molten rock beneath Earth’s surface

What is the difference between lava and magma?

Magma is underground; lava is at the surface

What is one mechanism for melting the mantle. Name the plate boundary where it occurs

Decompression melting at divergent boundaries

What is a second way to melt the mantle? Name the plate boundary where it occurs

Flux melting at convergent/subduction boundaries

What is a third way to melt the mantle? Name the plate boundary where it occurs.

Heat transfer melting at hotspot/continental curst settings

What are volatiles?

Substances with low boiling points like water and CO2

What is the difference between intrusive and extrusive igneous rocks

Intrusive cool underground and extrusive cool at the surface

What is the differnece between the sill and dike

Sill = horizontal intrusion; dike = vertical/cross-cutting intrusion

Name the 3 broad categories of sedimentary rocks

Clastic, chemical, biochem/organic

How are clastic sedimentary rocks classified

By grain size

Explain maturity and descriptive characteristics that contribute to it

Maturity reflects weathering/transport

Sediments are rounded, sorted, quartz -rich

Explain why fossils are found in sedimentary rocks - Example

Sediment bury and preserve remain EX: shells in limestone

What is the difference between body fossils and trace fossils

Body fossils are remains

Trace fossil are evidence of activity

What is the difference between breccia and conglomerate in terms of maturity

Breccia has angular clasts (immature) ; conglomerate has rounded clasts (more mature)

What is the law of superposition

Oldest layers are at the bottom, youngest at the top

What is the key component of limestone

Calcite

What are the two principle drivers of metamorphism

Heat and Pressure

3 types of metamorphism and how they relate to heat and pressure

Regional = heat + pressure over large areas

Contact = mainly heat near magma

Hydrothermal = hot fluids altering rocks

Protolith

The original rock before metamorphism

In what plate tectonic environment would you find blueschists and eclogites

Subduction zones

What is the protolith of marble and how does it form

Limestone; forms through recrystallization during metamorphism

What is a porphyroblast? EXAMPLE

a large metamorphic crystal; garnet

What does “high grade” mean in a metamorphic sense

Metamorphism under high temp and pressure

How does a metamorphic foliation form

Minerals align under directed pressure

How old is Earth is millions of years

4540 million

4.6 billion years ago

What geologic Eon are we currently living in

Phanerozoic Eon

When did the dinosaurs extinction happen

66 million years ago

Thinking about geochronology, if my zircon crystal had 100 uranium atoms to start with, how many does it have after 1 half life

05 uranium atoms

Thinking about geochronology, if my zircon crystal had 100 uranium atoms to start with, how many does it have after 3 half lives?

12.5

What was the cambrian explosion, and when did it happen on Earth

Rapid diversification of life about 541 million years ago

What is the difference between Eons, Eras, and Periods - Give example of each

Eons (largest and longest) ex: phanerozoic

Era: (eons subdivided, dramatic global changes like extinction) Mesozoic

Period: (a specific measurable stretch) - Jurassic Period

You are studying 2.5 Ga rocks. Why is U-Pb zircon geochronology more useful than C dating?

Carbon dating only works to ~50,000 years; U-Pb works for billions of years.

What happened during the Cryogenian Period

Major “snowball earth” glaciations occured

Can you explain the formation of the Moon? Impact on Earth

Giant impact with early earth - it stabilized Earths tilt and strong tides

Unconformity and how does it form

A gap in the geologic record - forms by erosion or non deposition followed by new deposition

What is the diff between stress and deformation

Stress is force on rocks; deformation is the resulting change in shape

Tension vs Compression

T: pulls apart

C: squeezes together

What is the diff between brittle and ductile deformation? EXAMPLES

B: breaks rocks = faults

D: bends rocks (folds)

Antiform and Synform

Antiform arches upward

Synform bends downwards

Anticline vs Antiform

Cline = has oldest rocks in center

Form = describes shape only

Faults, what does the hanging-wall refer to

The block above the fault plane

What is the diff between normal and reverse fault

Normal fault = hanging-wall moves down; reverse fault = hangingwall moves up

What is location at the surface of Earth where earthquake is centered

Epicenter

Location within the Earth where EQ happens

Hypocenter (focus)

P vs S waves

P waves travel faster than S waves

How can we use this velocity difference to identify the location of earthquakes?

differences in arrival times help calculate EQ location

4 factors that influence the human costs associated with an EQ

1. Magnitude

2. Population Density

3. Building quality

4. EQ depth

5. Time of day

What scale is used to measure the magnitude of EQ

moment magnitude scale

How does a magnitude 8 EQ compare to a magnitude 5 EQ in terms of energy

8 releases about 1000x more energy than a mag 5

Where does Erosion and deposition occur

Outside = erosion

Inside = deposition

Aquifers vs Aquitards

Aquifers: water storing rock layers

Aquitards: low permeability layers that block/slow water

An increase in oxygen-18 in ocean sediments implies what?

Earth was getting cooler

What is bornite and chalcopyrite?

Purple copper mineral
Gold copper mineral

Which is cheaper, surface mining or underground

surface

Which is more environmental damaged - surface or underground

surface

How does magma composition affect viscosity

More silica = thicker = explosive

What increases water density

low temp, high salinity, high pressure

4 main steps to get cooper into technology

1. The formation of a Copper
2. Mineral Exploration
3. Mining
4. Mineral Processing

What are critical metals

- improrant for tech/economy
- Limited supply
- Hard to replace
- Expensive/unstable supply