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