Quiz 17: Earths Interior and Geophysical Properties

Geologists study the composition of the Earth's crust using deep drill holes.

The asthenosphere may be a partially melted crystal and liquid slush.

Seismic tomography uses earthquake waves and computers to study cross sections of the mantle.

The Moho separates the crust from the mantle.

The force of gravity between two objects decreases as the square of the distance between the objects increases.

Seismic waves travel faster in oceanic crust than in continental crust.

Generally, seismic wave velocity decreases with depth.

Geologists think that the asthenosphere is molten.

The composition of the upper mantle is the ultramafic rock peridotite.

Most of the evidence for magnetic reversals comes from lava flows on the continents.

The average density of the Earth is 2.7 gm/cm³.

The presence of an S-wave shadow zone implies that the Earth's core is liquid.

The way that P-waves are refracted within the core suggests that there is a solid inner core.

The average heat flow of the continents is the same as the average heat flow of the sea floor.

The Earth's core is made up of equal parts cobalt and iron.

A gravity meter can be used to explore for metallic mineral deposits.

The concept of isostatic adjustment implies that all mountains extend to the same depth in the mantle.

The rise of the surface of the crust after removal of glacial ice is known as isostatic rebound.

A region held down out of isostatic equilibrium produces a negative gravity anomaly.

The greatest negative gravity anomalies in the world are found over oceanic trenches.

_____ is the branch of geology that applies physical laws and principles to study Earth. A) Earthquakology B) Physicalogy C) Geophysics D) Palentology E) Environmental geology

Recently, geologists have been analyzing ____ generated by tidal friction, ocean waves, and storms to gain an even more detailed image of the crust and upper mantle. A) energy waves B) light sources C) water movement D) evaporation E) ocean currents

Detailed images provided by _____ suggest that the mantle is heterogeneous, probably due to variations in temperature, composition, and density. A) p-waves B) shadow zone C) deep drill holes D) seismic reflection E) seismic tomography

_____ is a circulation pattern in which low-density material rises and high-density material sinks. A) Conduction B) Convection C) Density flow D) Refraction E) Reflection

A ____ is a tool used to study the gravitational attraction between Earth and a mass within the instrument. A) seismic reflection study B) sonograph C) gravitation recorder D) seismograph E) gravity meter

A region of magnetic force, called the ______ surround Earth. A) magnetic force B) magnetic field C) magma field D) magnetic poles E) magnetism

A gravity reading lower than the normal regional gravity indicates that a region is ____. A) actively being uplifted B) under a high magnetic field C) being held down D) a good prospect for an ore deposit E) undergoing elastic rebound

The study of ancient magnetic fields is called ____. A) paleontology B) old magnetism C) Curie point D) paleomagnetism E) magnetic polarities

A deviation from average reading is called a(n) ____. A) deviant B) negative C) anomaly D) above or below average E) positive

High _____ is usually an indication of a magma body or still-cooling pluton near the surface. A) geothermal gradient B) heat loss C) convection D) conduction E) heat flow

The bending of seismic waves as they pass from one material to another is called seismic ____. A) refraction B) reflection C) deflection D) attenuation E) waves don't bend when they pass through different materials.

The boundary that separates the crust from the mantle is the ____. A) mantle discontinuity B) Mohorovicic discontinuity C) lithospheric discontinuity D) athenospheric discontinuity E) shadow zone

The crust and upper mantle form the ____. A) lithosphere B) athenosphere C) core D) outer core E) Moho discontinuity

_____ is the return of some of the energy of a seismic wave to the Earth's surface after it bounces off a rock boundary. A) Seismic reflection B) Seismic refraction C) Seismic attenuation D) Seismic adjustment E) Seismic shadow zone

Seismic P-waves _____ through continental crust relative to oceanic crust. A) travel faster B) travel slower C) stay the same velocity D) are refracted E) are reflected

The upper mantle consists of _______. A) granite B) basalt C) ultramafic rocks D) metamorphic rocks E) sedimentary rocks

What is the asthenosphere? A) It is the surface that separates the crust from the mantle. B) It is the zone that separates the continental crust from the oceanic crust. C) It is in the surface that separates the inner and outer core. D) It is the zone of weakness in the mantle on which the lithosphere moves. E) It is the same as the Gutenberg Discontinuity.

The rise of the crust after removal of ice is called ____. A) crustal rebound B) tectonic uplift C) upheaval D) subduction E) dynamic adjustment

Continental crust is ___ relative to oceanic crust. A) the same thickness B) thinner C) thicker D) hotter E) of unknown relation

The P-wave shadow zone can be explained by the refraction of P-waves at the ___. A) core-mantle boundary B) asthenosphere-lithosphere boundary C) Moho D) inner core-outer core boundary E) 670 km depth limit

Iron-nickel meteorites are an important source of information regarding the composition of Earth's ______. A) oceanic crust B) core C) mantle D) asthenosphere E) continental crust

The ____ is the transition zone at the core-mantle boundary. A) Moho B) asthenosphere C) D layer D) perovskite zone E) unnamed surface

___ indicates that the core of the Earth is a liquid. A) Density calculations B) Studies of meteorites C) The P-wave shadow zone D) The S-wave shadow zone E) The Earth's heat flow

At a pressure equivalent to a depth of 670 km the mineral olivine collapses to form ____. A) perovskite B) quartz C) mica D) calcite E) zircon

The boundary between the core and the mantle is marked by great changes in ____. A) seismic velocity B) density C) temperature D) Both seismic velocity and density are correct. E) Seismic velocity, density, and temperature are all correct.

Hot mantle rock rising slowly by convection under parts of the ocean explains ____. A) mid-oceanic ridges B) underwater volcanoes C) the unexpectedly high heat flow under the oceans D) the thickness of the continents E) the location of earthquakes

_____ predicts that the higher a mountain range extends above sea level the deeper it extends into the mantle. A) Isostatic adjustment B) Crustal rebound C) Mantle convection D) Mohorovicic discontinuity E) Subducting oceanic lithosphere

Oceanic crust is _____ continental crust. A) thinner than B) thicker than C) the same thickness as D) the same composition as E) the same seismic velocity as

A cavity or body of low-density material causes a _____ pull on a gravity meter relative to average crust. A) stronger B) greater than the surrounding rock C) weaker D) rapidly increasing E) Gravity can't be measured.

A gravity meter registers _____ over ore bodies. A) zero gravity readings B) constant gravity C) decreased gravity D) increased gravity E) You can't explore for metallic deposits with a gravity meter.

As lava cools below the _____ point, a record of the Earth's magnetic field is permanently trapped in the rock. A) freezing B) burning C) boiling D) melting E) Curie

The rock record for tens of millions of years indicates that the Earth's magnetic field ____. A) reverses polarity about every 500,000 years B) is constant in strength and polarity C) did not come into existence until about 1 million years ago D) is a monopole magnet E) has steadily weakened and will be gone in another 10 million years

The ____ is a low velocity seismic zone. A) asthenosphere B) lower crust C) core D) outer core E) Mohorovicic discontinuity

Heat flow ______ the crest of the mid-oceanic ridges. A) increases away from B) decreases away from C) does not change relative to D) is unknown on E) is the highest on Earth on

The gradual loss of heat through the Earth's surface is called ___. A) thermal decay B) cooling trend C) heat flow D) thinning of the heat E) convection

Because _____ can be accurately calculated, the size and shape of the core can be determined. A) P-wave paths B) surface wave paths C) gravitational anomalies D) heat flow conditions E) magnetic anomalies

One widely accepted hypothesis is that the Earth's magnetic field is created by electric currents within the ______. A) asthenosphere B) crust C) lower mantle D) liquid outer core E) sun

_______ is a balance or equilibrium of adjacent blocks of brittle crust floating on the upper mantle. A) Density adjustment B) Isostasy C) Gravity adjustment D) Inertial adjustment E) Thermohaline flow

The average temperature increase in the shallow crust (the geothermal gradient) is about ______ degrees C per kilometer. A) 2 B) 5 C) 10 D) 15 E) 25

The magnetic poles are displaced about ______ degrees from the geographic poles. A) 5½ B) 11½ C) 16½ D) 30½ E) 45½