Geology 101 Midterm

What kind of plate margin exists today in East Africa?

divergent margin (continental rifting)

Why are andesitic rocks usually porphyritic?

two staged cooling history for andesitic magmas

What are the two most common elements comprising the ocean crust?

Silicon (Si) and Oxygen (O)

Which of the following answers is not correct regarding metallic bonds and properties of metals?

Strength doesn't depend on atomic radius and the type of crystal lattice

Divergent margins typically originate under continents because

The insulating property of thick continental lithosphere retains more heat than ocean lithosphere

Why do seismic waves decelerate as they enter the low velocity zone

The low velocity zone is at the pressure melting temperature for the Earth's mantle

What mechanism have geologists proposed to explain the uplift of the Colorado Plateau and the rifting of Nevada and Utah?

a spreading ridge was subducted under California and is now upwelling beneath the Basin and Range

S-waves are _______ as they travel through the outer core

absorbed

Which of the following answers is not a characteristic of a metal

all metals are anions (negatively charged ions)

Mount Fuji, Japan

andesite

Mount Rainier

andesite

Phillipines

andesite

The Olympic and Coast Mountains are composed of

andesite formed from a partial melt of the basaltic oceanic crust

Columbia plateau

basalt

Iceland

basalt

Valencies within the silicate tetrahedra of the mica structure are satisfied __________

by covalent bonds between adjacent oxygen atoms by ionic bonds with available cations

Source of lime for cement / marine limestone

carbonate

Primary waves are made up of______ waves, also known as push-pull waves. S waves are_____ waves, which means they vibrate up and down, perpendicular to the motion of the wave as they travel.

compression, transverse

Which tectonic margin would tend to have deep and shallow focused earthquakes

convergent

P-waves _________ as they travel through the outer core

decelerate

Following differentiation the Earth became compositionally zoned according to

density of constituent matter

Diamond is harder than graphite because

diamonds have covalent bonds between its constituent atoms while graphite has vanderwahl bonds

Transform plate boundaries are typically associated with ___________.

divergent margins where the rate of spreading is different along segments of the spreading ridge

P waves travel ______ than S waves

faster

Pheoncryst Crystals ______ and at a _________ temperature than the minerals within the ground mass in porphyritic rocks.

first, higher

Ural

granite

Mineral group vital to proper cell function in human beings

halide

What is the significance of (OH) in the mica crystal structure?

it is water likely incorporated during the subduction process

S waves are generally ______ than P waves and are often responsible for the damage that an earthquake may cause.

larger

Which of the following statements below is incorrect regarding metallic bonds?

metallic atoms have a strong connection to their electrons, which are fixed around the nucleus AND metals are generally poor conductors of heat and electricity

The most widely accepted explanation for the earth's magnetic field is

movement of electrons in the molten iron of its outer core

Andes mountains

ocean-continental subduction

What formed during the differentiation process?

oceans and atmosphere

silicate tetrahedron has a net charge of

-4

During differentiation of the Earth, heat was generated from

-Kinetic energy of impacting planetesimals -Compressional heating during condensation of planetesimals -Radioactive heating

What evidence have geologists/ geophysicists used to support the contention that the core is metallic and has a liquid component?

-Seismic wave studies, specifically the S-wave shadow zone -The presence of the earth's magnetic field

What scientific observations of the solar system indicate that the sun and planets formed from a rotating, disk-shaped, nebular dust cloud?

-The planets all revolve in a counter clockwise direction around the sun -Most all of the planets and their moons rotate on their axes in a counter clockwise direction -The planetary orbits are aligned along the suns equatorial plane

How can one best explain the seismic wave properties shown in the above diagram.

-refraction of seismic waves due to density changes -absorption of seismic waves due to phase change from a solid to a liquid

Quartz ratio

1 : 2

Mica crystal structure ratio silicate

1 : 2.5

Amphibole ratio of Si:O in the tetrahedral structure

1 : 2.75

How can we best explain the fact that the inner and outer cores are both composed of metallic iron (Fe) and nickel (Ni) yet the outer core is a liquid and the inner core solid?

The melting temperature for iron nickel is lower than the geothermal gradient temperature in the outer core

Which of the following bond strength rankings are in the correct order from weakest to strongest

Van der Waal, metallic, ionic, covalent

Magnetic minerals that crystallize in a lava flow erupted at polar latitudes today will

be oriented parallel to the surface of the lava flow, will have a normal polarity and point north

How does the silicate tetrahedron achieve charge balance in the mineral quartz?

it will share electrons between oxygen atoms, it will form ionic bonds with available cations, it will form metallic bonds with available cations

Source of iron

oxide

Why do the large Jovian planets have molecular hydrogen in their atmospheres, but the smaller terrestrial planets do not?

the Jovian planets are further from the sun and the hydrogen gas can condense and be held by gravity

A partial melt of the asthenosphere will not rise toward the surface because

the above statement is false because an asthenospheric melt will rise towards the surface

Why is there a low velocity zone for seismic waves entering the asthenosphere?

the asthenosphere is a partial melt and seismic wave decelerate as they enter the phase change

What kind of tectonic setting is represented by the Ural Mountains, which separate Asia from Europe?

Ancient collision margin (continent-continent)

Which zone of the Earth is also described as the "low velocity zone?"

Asthenosphere

Volcanic arc

Cascades

Backarc basin

Columbia Plateau

Arrange the compositional zones of earth according to their respective density (lightest to densest)

Continental crust, ocean crust, mantle, outer core, inner core

Two most common elements comprising the outer core

Iron (Fe) and Nickel (Ni)

Meteorites that strike the Earth are predominantly composed of

Iron-nickel and silicate minerals

Australia has unique faunal (animal) assemblages compared to the other continents because __________.

It has been tectonically isolated from other continents for a very long period of time.

The melting temperature of _______ must be reached in order for the Earth to become compositionally zone:

Metallic Fe and Ni

Which volcanic gas was not added to the Earth's atmosphere during early differentiation of the planet?

O2

Accretionary wedge with coastal mountains

Olympic or coastal mountains

Why are P-waves completely absorbed as they enter the outer core?

P-WAVES ARE NOT COMPLETELY ABSORBED IN THE OUTER CORE

Forearc basin

Puget lowland

Yellowstone

Rhyolite

What are the mechanisms that likely drive subduction of the ocean lithosphere?

Ridge push AND Plate Sliding AND Slab pull

P waves can travel through any kind of material, whether it is a solid, liquid or gas because of their wave movement.

S waves, on the other hand, can only move through solids and are stopped by liquids and gases.

What type of seismic wave shadow zone is shown in the image above?

S-wave

Why is the S-wave shadow zone larger than the P-wave shadow zone?

S-waves ARE completely absorbed by the liquid outer core

Why are S-waves completely absorbed as they enter the "low velocity zone" (asthenosphere)?

S-waves are not completely absorbed by the asthenosphere

How are minerals produced on earth

only answers a and c are correct a- minerals can crystallize directly from a magmatic melt c- minerals can precipitate from aqueous solutions

asthenosphere

peridotite

Source of lead (metallic ore bodies)

sulfide

What makes the asthenosphere unique relative to the lowermost lithosphere and the uppermost mesosphere (upper mantle)?

the asthenosphere is at the pressure melting temperature for the upper mantle composition

When two ocean plates converge

the older plate will be subducted

Why do terrestrial planets have so little molecular (gaseous) hydrogen?

the terrestrial planets are close to the sun and the low density hydrogen was lost to space

Why does quartz develop six cleavage planes?

this mineral does not cleave

Why does sodium-rich plagioclase develop cleavage planes yet it is a framework silicate mineral with all its oxygen atoms shared between tetrahedra?

this mineral does not cleave

Why does Ca-rich plagioclase develop cleavage planes yet it is a framework silicate mineral with all its oxygen atoms shared between tetrahedra?

this mineral may have an Al atom in its tetrahedra which requires additional ionic bonds with Ca atoms