Geo 303 Exam 1

What is the age of the oldest intact rocks that have been found on Earth?

4 Ga

How does the Doppler Effect tell us about the motion of galaxies?

Light from galaxies moving away from us has a lower frequency (I.e. looks redder) than light from galaxies that are moving towards us.

The earliest matter in the universe was composed of mostly

hydrogen and helium

The earth is referred to as a layered planet because

differentiation during and following planetary accretion allowed the materials making up the early Earth to separate based upon their density

What is the most probable origin of earth's moon?

condensed from material expelled from a gigantic collision between the proto-earth and a Mars-size impacting body

According to current scientific understanding, the age of our universe is

about three times older than the age of the earth

All of the following statements about the atmosphere of the early Earth are correct except one. Which statement is incorrect?

The development of Earth's magnetic field caused the atmosphere at that time to be driven off.

The Earth's layers are composed of which of the following, from outside to inside

(Si,Al,O); (Mg,Fe,Al,O); (Fe,Ni)

What information can meteorites provide about Earth?

the composition of Earth's core, Earth's age, the average composition of the whole Earth

According to nebular theory, the progression from planetesimal to full-fledged planet is propelled mainly by which of the following?

gravity

Alfred Wegner is best remembered for

being the first to put together a hypothesis for continental drift based on a variety of scientific data sources

Which part of the earth do geophysicists think generates it magnetic field? The earth's

core

Which statement about magnetic reversals is correct?

Reversals are random; we cannot predict when the next reversal will occur.

Magnetic declination refers to

the angular difference between a compass reading at a certain location and the direction of the True, or Geographic North Pole

Why can the earth's inner core not act as a permanent magnet?

Its temperature is far hotter than the Curie temperature for any magnetic material

If a flow of basalt were to cool and crystallize at the magnetic South Pole, what would be the orientation of its locked-in magnetic lines of force?

vertical to the earth's surface

Over the past 30 thousand years, what has been the relationship between the North magnetic pole and North geographic (rotational) pole?

Although the geographic pole is constantly moving in random directions, it always stays near to the magnetic pole

The geodynamo generates currents within the liquid outer core that are responsible for

generating most of the earth's magnetic field

Which one of the following is not a piece of evidence used by Wegner to argue for continental drift?

magnetic reversals in ocean floor basalts show a mirror imagine across mid ocean ridges

The difference between a theory and a hypothesis is

a theory is well tested

What takes place in convergent boundaries?

Deep and shallow earthquakes, recycling of old oceanic crust, and volcanic arcs

What takes place in divergent boundaries?

New oceanic crust and shallow earthquakes and volcanic activity

What takes place in transform boundaries?

Earthquakes but no volcanic activity

1st step of continental rift formation

The lithospheric mantle begins to stretch horizontally and thin vertically

2nd step of continental rift formation

The crust fractures, and faults develop

3rd step of continental rift formation

Large fault blocks of crust slide down into the widening rift

4th step of continental rift formation

Magma erupts as lava, creating volcanoes along and near the center of the rift

What is true about Hawaii's Hot Spot

It produced the Hawaiian Islands and it produced the Emperor Seamounts

What formed the Red Sea?

rifting followed by seafloor spreading

transfrom boundary

slides past each other

convergent boundary

moves toward each other; subduction

divergent boundary

moves away from each other; rifting/ seafloor spreading

1st event that occurs between the mid-ocean ridge and deep-ocean trench

oceanic crust created

2nd event that occurs between the mid-ocean ridge and deep-ocean trench

sediment accumulates on oceanic crust

3rd event that occurs between the mid-ocean ridge and deep-ocean trench

oceanic crust scraped off plate to form accretionary wedge

4th event that occurs between the mid-ocean ridge and deep-ocean trench

oceanic crust recycled into mantle

1st step on how scarps typically form at a mid-ocean ridge

asthenosphere rises beneath the ridge and begins to melt

2nd step on how scarps typically form at a mid-ocean ridge

magma rises and accumulates under the ridge axis

3rd step on how scarps typically form at a mid-ocean ridge

cooling causes the formation of gabbro and basalt dikes

4th step on how scarps typically form at a mid-ocean ridge

oceanic crust moves (spreads) away from the ridge axis

5th step on how scarps typically form at a mid-ocean ridge

tension causes breaks and results in the formation of faults

6th step on how scarps typically form at a mid-ocean ridge

slipping causes divergent-boundary earthquakes

The oldest seafloor is generally less than 200 million years old. Why?

All oceanic lithosphere eventually gets subducted beneath the continents by the time it is 200 million years old.

Three types of ion configurations

Tetragonal, octahedral, and cubic

Why do the minerals in a geode form euhedral crystals rather than anhedral grains?

The crystals have abundant room to grow within a rock cavity.

What is the prime characteristic that geologists use to separate minerals into classes?

Chemical composition - specifically, the anions in the chemical formula

Outer atoms in a silica-oxygen tetrahedron

4 oxygen

Inner atom in a silica-oxygen tetrahedron

silicon

the silica-oxygen tetrahedra is the building block of which chemical class of minerals?

Silicates

Which of the following classes of minerals are most abundant in the Earth's crust and mantle?

silicates; 95%

Adjectives for mineral luster

earthy, glassy, metallic

The hardness of a mineral is determined by

its ability to resist being scratched by other substances; Mohs hardness scale

Obsidian is a volcanic glass that forms when lava cools very quickly and consists of a solid mass of glass through and through. Why is obsidian not classified as a mineral?

The atoms or molecules in obsidian do not have a crystalline structure.

The smallest structural unit describing the repeating pattern in a minerals crystal structure is the unit cell. Is the following true or false? The chemical formula for the unit cell is the same as that of the mineral.

False

The structural arrangement of atoms in the crystal lattice of a mineral is most strongly determine by

the size of anions

Isomorphic minerals share which of the same properties

crystal structure

Compounds with the same chemical formula are always the same mineral

False

Of the bonds we talked about, the strongest in minerals is the

Covalent

Compounds made up of 2 nonmetals from which kind of bond?

covalent

Olivine, a high temperature mineral, is highly susceptible to weathering because

individual covalently bonded silicate structures are linked via weak, ionic bonds with metal ions

According to the periodic table, an element has the following electron shell configuration: {2, 8, 7}. Which type of bond is it most likely to form with a nonmetal?

covalent

Bowen's reaction series describes

the relationship between mineral crystallization from a melt and temperature and composition

The presence or absence of cleavage in a mineral indicates

whether there are planes through the crystal structure with relatively sparse and/or weak atomic bonds

What composition of magma is produced by melting at lower temperatures?

felsic and intermediate

What composition of magma is produced by melting at higher temperatures?

mafic and ultra-mafic

What happens when a rock moves up in the Earth?

It is subjected to slightly lower temperatures and much lower pressures, and it begins to melt.

Identify the factors that cause melting and thus the formation of magma.

addition of volatiles, heat transfer, and decompression

1st step in fractional crystallization

magma, after entering through the bottom of the magma chamber, reaches the top of the chamber

2nd step in fractional crystallization

magnesium- and iron-rich minerals begin to crystallize

3rd step in fractional crystallization

Mineral crystals, having a higher density than liquid magma, sink to the bottom of the magma chamber

4th step in fractional crystallization

The magma shifts toward a more intermediate composition

What does grain size generally indicate about the cooling of a melt?

larger crystals indicate the melt cooled gradually

Which factors control the cooling time of magma within the crust?

the volume of the intruded magma and the depth at which the magma cools

intrusive igneous rock

igneous rock that formed below Earth's surface

extrusive igneous rock

Rock that forms when magma cools above the surface of Earth

Four tectonic settings of igneous activity

continental rift, hot-spot volcano, mid-ocean ridge, and subduction zone

Pluton creates what kind of texture of igneous rock?

Crystalline texture

Explosive eruption creates what kind of texture of igneous rock?

Fragmental texture

Lava flow creates what kind of texture of igneous rock?

Glassy texture

The image shows Mount St. Helens two years after its 1980 eruption. Given the shape of the volcano and presence of a lava dome (source of the steam), what is the most likely composition of the associated magma?

felsic to intermediate

An explosive volcanic eruption does not produce lava flows because

the sudden release of accumulated gas pressure blasts the lava upwards, forming pyroclastic debris

Viscosity

A liquid's resistance to flowing

Scientists estimate the recurrence interval of eruptions at Yellowstone caldera is about 730,000 years. Which of the following statements best describes the recurrence interval of Yellowstone caldera?

Yellowstone erupts on average about every 730,000 years, but it may erupt sooner or later than that.

How can you tell when polarity reverses or moves?

Based on the polarity of old rocks; once rocks cool below the curie temperature, their polarity is locked in and can't change, making it relatively easy to connect the dots on when the magnetic field flipped or the poles moved.

Alfred Wegner is best remembered for

being the first to put together a hypothesis for continental drift based on a variety of scientific data sources

Which part of the earth do geophysicists think generates its magnetic field? The earth's:

core

3. Which statement about magnetic reversals is correct?

Reversals are random; we cannot predict when the next reversal will occur.

Magnetic declination refers to:

the angular difference between a compass reading at a certain location and the direction of the True, or Geographic North Pole

Why can the earth's inner core not act as a permanent magnet?

Its temperature is far hotter than the Curie temperature for any magnetic material

If a flow of basalt were to cool and crystallize at the magnetic South Pole, what would be the orientation of its locked-in magnetic lines of force?

vertical to the earth's surface;

The geodynamo generates electric currents within the liquid outer core that are responsible for:

generating most of the earth's magnetic field;

Over the past 30 thousand years, what has been the relationship between the North magnetic pole and North geographic (rotational) pole?

Although the geographic pole is constantly moving in random directions, it always stays near to the magnetic pole.

Which one of the following is not a piece of evidence used by Wegner to argue for continental drift?

magnetic reversals in ocean floor basalts show a mirror image across mid ocean ridges

the difference between a theory and a hypothesis is

a theory is well tested