Ch2 practice questions

Boundaries between Earth's layers: are unreachable to humans, so they must be studied by indirect methods. are defined by abrupt changes in earthquake wave velocities. are places where there's abrupt change in the density of rock. divide the Earth into three major layers (crust, mantle, and core) and several sublayers. All of the above are true statements.

All of the above are true statements.

Identify the TRUE statement. Most meteoroids are fragments derived from the Oort Cloud, Kuiper Belt, or asteroid belt; some are chips of the moon or Mars. Meteoroids that explode into fireballs are termed bolides. Catastrophic collisions of meteoroids with Earth are rare, but have happened during Earth's past and probably will happen again. A glowing streak of atmospheric gas roughly 150 km high is termed a meteor ("shooting star"). All of the above are true statements.

All of the above are true statements.

Which of the following statements concerning density is TRUE? Earth's density is a little over 5 g/cm3. The density of crustal rock is between 2.2 and 2.5 g/cm3. Mafic rock is denser than felsic rock. Changes in density can be detected by changes in seismic wave velocity. All of the above are true statements.

All of the above are true statements.

Which of the following statements is TRUE? Peridotite: is rare at Earth's surface. is the most abundant rock of Earth. is ultramafic. is very rich in iron and magnesium, very poor in silica. All of the above are true statements.

All of the above are true statements.

Which of Earth's layers account for the least of the volume of Earth?

Crust

A rock is a solid organic substance in which atoms are arranged either in an orderly pattern (crystalline) or as irregularly shaped grains; a mineral is an aggregate (mixture) of rocks.

False (A rock is an aggregate of minerals; a mineral is a solid inorganic crystalline substance.)

A vacuum is an area that contains absolutely no matter.

False (A vacuum is an area with very little matter. For example, interstellar space is a vacuum with less than 1 atom per liter, and interplanetary space is also a vacuum but with about 5,000 atoms per liter. )

The geothermal gradient increases as you go deeper into the Earth.

False (Although the temperature increases with depth, the geothermal gradient decreases from about 15 to 50°C per km near the surface to 10°C per km or less in the core.)

Silicon is by far the most abundant elements of Earth's crust; oxygen is the second most abundant.

False (Because oxygen bonds to other elements to form many minerals, it accounts for about half (by weight) and more than 90% (by volume) of Earth's crust.)

Lithosphere and crust are synonymous.

False (Lithosphere means all of the rock that lies on top of the asthenosphere, and this includes the crust and the uppermost part of the mantle.)

Iron, oxygen, silicon, and potassium make up most of the mass of the whole Earth.

False (Potassium does not belong in the list; magnesium does.)

Roughly 50% of Earth's surface is covered by hydrosphere.

False (Roughly 70% of the Earth's surface is covered by hydrosphere.)

The asthenosphere is largely liquid and flows at rates of 10 to 15 km per year.

False (The asthenosphere is largely solid, but it's hot and soft enough to flow very slowly, roughly 10 to 15 cm per year.)

A cross-section cut through the Earth would reveal a very thin atmosphere surrounding a thin crust of low-density rock, all shifting around slowly on an internal sea of semi-liquid rock (magma)

False (The interior of Earth is essentially solid; only the outer core is liquid.)

The inner core is so hot, it's liquid, and therefore some seismic waves can't travel through it.

False (The outer core, not the inner core, is liquid and impedes travel of some seismic waves. )

The core accounts for most of the volume of Earth.

False The mantle accounts for most of the volume of Earth. (Section refs: 2.5, p. 46)

The deepest well ever drilled penetrates the upper half of the continental crust.

False (Continental crust is at least 35 km thick; the deepest well, in northern Russia, is only 12 km deep. (Section refs: 2.4, p. 42))

The Moho lies below the lithosphere-asthenosphere boundary.

False (Since the Moho is the boundary between the crust and the mantle, and the lithosphere consists of the crust and the top part of the mantle (down to the asthenosphere), the Moho must lie above the lithosphere-asthenosphere boundary. (Section refs: 2.5, p. 46))

Which of the following statements concerning density is false?

Felsic rock is denser than mafic rock

Identify the TRUE statement

Hot molten rock that cools and hardens produces igneous rocks

Identify the FALSE statement: Metamorphic rocks form when preexisting rocks undergo changes in response to heat and pressure. Hot molten rock that cools and hardens produces igneous rocks. Sedimentary rocks form when preexisting rock grains are cemented together. Sedimentary rocks form when minerals precipitate out of a water solution. Magma is the term for very hot rock that is molten; when it cools and hardens, it's called lava.

Magma is the term for very hot rock that is molten; when it cools and hardens, it's called lava. (Both magma and lava are terms that denote molten rock. Lava is molten rock that has flowed out on Earth's surface; magma is molten rock that remains beneath the surface. )

The two most common gases of Earth's atmosphere and their percentages are

Nitrogen (N2) 78%, and Oxygen (O2) 20%

Which of the following statements is FALSE? The Moho marks the boundary between the lithosphere and the asthenosphere. Continental crust can be four times as thick as ocean crust. Continental crust is less mafic than ocean crust. Ocean crust is denser than continental crust. Ocean crust consists of basalt and gabbro; continental crust consists of a great variety of rock types.

The Moho marks the boundary between the lithosphere and the asthenosphere. (The Moho marks the boundary between the crust and the mantle.)

Identify the FALSE statement. The geothermal gradient is the rate of change in temperature with depth in Earth. The temperature at Earth's center may almost equal the temperature of the Sun's surface. The pressure at Earth's center is millions of times greater than normal atmospheric pressure. The calculated density at Earth's center makes scientists almost certain the inner core is composed of gold. Since land surface does not rise and fall as ocean surface does, Earth's interior cannot be largely liquid.

The calculated density at Earth's center makes scientists almost certain the inner core is composed of gold. (Unfortunately, density calculations and studies of metallic meteorites suggest a core of iron alloy, not gold.)

Which of the following statements about the crust is FALSE? The crust is the top of the mantle that has cooled and hardened. The upper portion of the crust contains microscopic pores that contain groundwater. The crust plus the upper part of the mantle make up the lithosphere. There are two different types of crust: oceanic and continental. The crust-mantle boundary occurs at different depths in different locations.

The crust is the top of the mantle that has cooled and hardened. (The crust is not simply cooled mantle; rather, it consists of rocks created from elements brought to the surface in magma.)

Mantle rock becomes soft enough to flow at about 1,280°C.

True

Basalt, gabbro, and peridotite are all mafic or ultramafic, but basalt has small grains and the others have large grains.

True (Basalt is a fine-grained mafic rock; gabbro and peridotite are coarse-grained mafic and ultramafic rocks respectively.)

Earthquakes are generated when rock moves along faults.

True (Movement along faults is the most common cause of major earthquakes. )

The Van Allen radiation belts serve as a trap for cosmic rays and thus shield life on Earth from excessive radiation.

True (The Van Allen radiation belts trap cosmic rays and shield Earth from excessive radiation. (Section refs: 2.2, p. 38))

Boundaries between the earth's layers

are places where there is an abrupt change in the density of rock

Which of the following statements is FALSE? Peridotite is

felsic

Choose the list that shows rock composition decreasing in silica and increasing in iron and magnesium. granite, basalt, peridotite peridotite, basalt, granite basalt, peridotite, granite granite, peridotite, basalt The question is invalid; they're all equally rich in iron and magnesium.

granite, basalt, peridotite (Granite is a felsic (rich in silica) rock; basalt is a mafic rock; and peridotite is an ultramafic rock. (Section refs: 2.3, p. 42))

Which of the following would you consult to predict the effect of sea level changes on the amount of exposed land areas? seismic velocity graphs hypsometric curve ship's log of the Glomar Challenger readings of a magnetosphere All would be relevant.

hypsometric curve (The hypsometric curve shows at a glance what percentage of land lies at what elevation.)

Which of the following groups of elements make up the most mass of the whole earth?

iron, oxygen, silicon, magnesium

The two most common gases of Earth's atmosphere and their percentages are: carbon dioxide (CO2) 21%, and oxygen (O2), 78%. water (H2O), 21%, and oxygen (O2), 78%. oxygen (O2), 21%, and carbon dioxide (CO2), 78%. nitrogen (N2), 21%, and oxygen (O2), 78%. nitrogen (N2), 78%, and oxygen (O2), 21%.

nitrogen (N2), 78%, and oxygen (O2), 21%. (Earth's atmosphere consists of 78% nitrogen and 21% oxygen, with minor amounts of argon, carbon dioxide, neon, methane, ozone, carbon monoxide, and sulfur dioxide.)

Identify the FALSE statement. Earth's surface varies in composition and elevation: 70% is surface and subsurface water (the hydrosphere). extensive regions are ice covered (the cryosphere). the topography (ups and downs of the land surface) varies from 1,300 feet below sea level to 29,035 feet above sea level. most land lies less than 1 km (0.6 miles) above sea level. only the sea floor is a relatively flat surface.

only the sea floor is a relatively flat surface. (Although most of the sea floor lies between 4 and 5 km below sea level, in places it reaches a depth of 11 km below sea level. It definitely is not flat. (Section refs: 2.3))

Identify the FALSE statement. The categories of materials that constitute Earth include: glasses; solids in which atoms are not in any orderly pattern. volatiles; materials that easily become gases at ordinary Earth surface temperatures. organic chemicals; all carbon-containing compounds, including oil, protein, carbon dioxide, and calcium carbonate. alloys; mixtures of more than one type of metal atom. melts; solid materials that have melted due to heat.

organic chemicals; all carbon-containing compounds, including oil, protein, carbon dioxide, and calcium carbonate. (Organic chemicals are a category of Earth material, but they include only the carbon compounds that occur in living organisms. Carbon dioxide and calcium carbonate are not considered organic. )

Earth's magnetic field is generated in the

outer core

Choose the list that accurately shows rock composition increasing in silica and decreasing in iron and magnesium

peridotite, basalt, granite

Which of the following is caused by the interaction of the solar wind with magnetic lines of force and gases in polar regions? the Van Allen belts the aurorae a vacuum a dipole the heliosphere

the aurorae (Contrary to answer A, the Van Allen belts are areas composed of solar wind particles and cosmic rays. Contrary to answer C, a vacuum is an area that contains very little matter. Contrary to answer D, a dipole is a magnetic field that has a north pole and a south pole. Contrary to answer E, the heliosphere is a region of space far beyond Earth's orbit in which the few atoms present come from the solar wind)