midterm 1

Question 1

approx. how long ago did the supercontinent pangea exist?

Answer 1

200M years ago

Question 2

T/F minerals in phaneritic rocks are visible to the naked eye

Answer 2

True

Question 3

there are 23,000 yr old footprints discovered at white sands national park and are examples of what type of sedimentary structure?

Answer 3

trace fossil

Question 4

in which of the following volcanic settings are you most likely to find pillow basalts

Answer 4

mid-ocean ridge volcano

Question 5

lithospheric plates move at a velocity approx. equivalent to:

Answer 5

fingernails grow

Question 6

which of the following physical properties are used to identify minerals?

Answer 6

hardness, density, cleavage, luster, streak

Question 7

while vacationing on the beautiful papakolea green sand beaches of hawaii, you reach down and pull up a hand full of olive-green material?

Answer 7

olivine

Question 8

rank these sedimentary rocks by the transport energy of their depositional environment: conglomerate, sandstone, shale, siltstone

Answer 8

low energy: (more fine grained)
shale, siltstone, sandstone, conglomerate
high energy (more coarse)

Question 9

how is magma produced at the subduction zone?

Answer 9

water reduces the melting temp along with the subduction interface

Question 10

T/F deposition refers to the processes that dislodge particles of rock produced by weathering

Answer 10

False

Question 11

gold miners in northern california used hydraulic mining to concentrate gold from which type of ore deposit in the sierra nevada mountains?

Answer 11

placer deposits

Question 12

which type of metamorphism is defined by high temperature and low pressure conditions?

Answer 12

contact metamorphism

Question 13

match the plate boundary type to the appropriate descriptor.
- convergent (ocean-ocean subduction)
- convergent (continent-continent collision)
- transform
- divergent

Answer 13

• destructive
• destructive
• conservative
• constructive

Question 14

T/F the earth’s crust includes the entire lithosphere and part of the upper mantle

Answer 14

False

Question 15

whats the approx temperature magnitude at which rocks begin to melt

Answer 15

1000C

Question 16

according to bowen’s reaction series, which mineral is the first to crystallize from a melt?

Answer 16

olivine

Question 17

which calcium-magnesium carbonate mineral is rarely, if ever, observed in modern depositional environments

Answer 17

dolomite

Question 18

which kind of volcanic eruption produced the rope-like, low-viscosity pahoehoe lava?

Answer 18

hawaiian

Question 19

which of the following atomic properties are most important for element substitution in a mineral lattice?

Answer 19

atomic charge

Question 20

what is the primary difference between a breccia and a conglomerate

Answer 20

angularity, breccias are angular and conglomerates are round

Question 21

T/F color is the most reliable way to identify a mineral

Answer 21

False

Question 22

what is the most abundant group of mineral in the crust and mantle

Answer 22

silicates

Question 23

what is the typical geothermal gradient in a stable continental interior (i.e a “craton” away from an active plate boundary)?

Answer 23

30˚C/km

Question 24

which of the following processes are part of sedimentary lithificaiton?

Answer 24

cementation, compaction

Question 25

a figure illustrates magnetic anomalies along the axis of the mid-atlantic ridge, south of iceland. why are the magnetic anomalies symmetric?

Answer 25

the spreading velocity is equal on both sides of the ridge

Question 26

whats the primary difference between chert and flint?

Answer 26

no difference, these are two names for the same rock

Question 27

whats the name for the preexisting rock into which magma is intruded?

Answer 27

country rock

Question 28

alfred wegener's evidence for his theory of continental drift was derived from... (4 answers)

Answer 28

- fossil assemblages - geologic structures (orogens) - glacial deposits - rock types and ages

Question 29

T/F a granoblastic rock texture forms in metamorphic rocks subject to high differential stresses

Answer 29

False

Question 30

the primary difference between a stock and a batholith is:

Answer 30

area extent, batholiths are > 100km2

Question 31

T/F metasomatism is a type of metamorphism where rock chemistry changes primarily due to fluid alteration

Answer 31

True

Question 32

grain sorting in a sediment can be understoof as what statistical property of a sediment's particle size (or grain size)?

Answer 32

variance (or std)

Question 33

the silicate tetrahedron, building block of silicate minerals, has a chemical formula SiO4. if the mineral quartz is composed entirely of silica tetrahedra, why is the chemical formula for quartz SiO2?

Answer 33

the oxygen atoms are covalently bonded between silicate tetrahedra

Question 34

which of the following characteristics define a mineral: - usually inorganic - specified chemical composition - naturally occurring - rare - solid crystalline

Answer 34

- usually inorganic - specified chemical composition - naturally occurring - solid crystalline

Question 35

why is there no active volcanism in the himalaya today?

Answer 35

subduction of the indian plate is too shallow

Question 36

T/F evidence from seismic tomography favors whole mantle convection instead of stratified mantle convection

Answer 36

True