Chapter 03 Continental Drift

All basalts younger than 700,000 years old ____________. a. are found on the continents b. have normal magnetic polarity c. are found on the ocean floor very far from mid-ocean ridges d. have reverse magnetic polarity

The apparent tendency of the north (or south) magnetic pole to vary in position over time is termed ____________. a. magnetic declination b. dipole c. magnetic inclination d. polar wander

Limestone reefs and salt deposits are important rocks in the reconstruction of Earth history because they ____________. a. automatically provide age information; all such deposits occurred between 200 and 400 million years ago b. are deposited in warm climates today, but there is good reason to think that they were deposited in cold climates millions of years ago c. imply that ancient human societies had access to good snorkeling and premium margaritas d. can be used to infer the ancient climate of the Earth; they are deposited in environments that are restricted to warm climate

It is not the continents that move relative to a fixed pole, but rather it is the pole that moves relative to fixed continents. a. false b. true

Sea-floor spreading is driven by volcanic activity ____________. a. along mid-ocean ridges b. in the middle of abyssal plains c. at the edges of continental shelves d. along fracture zones

The apparent polar wander path obtained from magnetite crystals in basalts on the North American continent is now interpreted to be the result of ____________. a. drifting of the North American continent b. wandering of the geomagnetic North Pole

Evidence of paleomagnetism can be found in _________________. a. basalt that has cooled from lava b. any rock with magnetic minerals present c. sedimentary rocks where minerals form from ion-bearing groundwater d. All of the above are correct.

The oldest basalts on the ocean floor are about ____________ years old. a. 4 billion b. 2.5 million c. 50 thousand d. 200 million

If a geologist discovered coal in a modern-day cold, snowy location, he or she could conclude that _____________. a. this discovery was anomalous b. the area was once covered with an ocean c. the area was once covered with swamps and/or jungles d. a meteorite must have struck the area

The term and concept of sea-floor spreading (see figure below) was developed by _____________. a. Wegener and Dietz b. Hess and Wegener c. Hess and Dietz d. Wegener

The age of oceanic crust ____________ with increasing distance from a mid-ocean ridge. a. decreases b. increases

Volcanoes that have submerged beneath the surface of the sea are termed ____________. a. fracture zones b. guyots c. mid-ocean ridges d. continental rises

The thickness of clay and planktonic microskeletons is greatest ____________. a. along fracture zones b. along mid-ocean ridges c. in the center of abyssal plains d. at the edges of ocean basins

Regions of the sea floor with positive magnetic anomalies were formed during times when Earth's magnetic field ____________. a. was exceptionally strong b. was exceptionally weak c. had reversed polarity d. had normal polarity

A compass today points directly to geographic north. a. true b. false

Wegener proposed continental drift after he observed evidence from fossils, glacial deposits, and the fit of the continents that suggested all of the continents were once ____________. a. combined to form a supercontinent (he termed Pangaea) in the Late Paleozoic through the Mesozoic b. combined to form a supercontinent (he termed Rodinia) in the Proterozoic c. aligned east to west along the equator during the Late Mesozoic through the Cenozoic d. aligned north to south along the prime meridian during the Late Cenozoic

In Wegener's evidence for continental drift, continents were proposed to fit together, such as the east coast of South America with the __________________ and the upper west coast of Africa with the _______________. a. west coast of Europe; east coast of South America b. lower west coast of Africa; east coast of South America c. west coast of Europe; east coast of North America d. lower west coast of Africa; east coast of North America

If you were using both a compass and a map marked with latitude and longitude to navigate, you might note the angle difference between your compass and what is marked on the map, called _____________. a. magnetic declination b. magnetic inclination c. magnetic reversal d. magnetic dipole

Currently, most geologists ____________. a. agree that continental drift occurs; the mechanisms that drive drift are at work in the lower mantle and outer core and were unknown in Wegener's time b. continue to reject continental drift c. agree that continental drift occurs; the mechanisms that drive drift are at work in the ocean basins and upper mantle and were unknown in Wegener's time d. agree that continental drift occurs, but they still do not understand why it occurs

If we mentally align the continents to fit Wegener's concept of Pangaea, evidence of Late Paleozoic glacial deposits ____________. a. is more difficult to explain than in the modern continental configuration b. makes very little sense in either the Pangaea configuration or the modern configuration c. is much more readily explained than in the modern continental configuration

An average everyday compass depicts inclination. a. false b. true

The theory of plate tectonics is a theory because it _____________. a. was discovered so long ago b. is widely accepted c. is not widely accepted d. cannot be directly proven

According to the figure below, fracture zones lay roughly ___________ to mid-ocean ridges. a. adjacent b. at an obtuse angle c. parallel d. perpendicular

A great boost in sea-floor exploration and a greater understanding of sea-floor bathymetry was a result of _______________. a. military needs in World War II b. military needs in World War I c. scientific advances in the 1920s d. scientific advances in the 1950s

Spreading rates along mid-ocean ridges have ____________. a. been remarkably constant through time b. changed through time, and today vary between 1 and 10 m/yr c. changed through time, but are the same everywhere on Earth today d. changed through time, and today vary between 1 and 10 cm/yr

What mineral is integral to paleomagnestim? a. magnetite b. potassium feldspar c. iron d. quartz

This map depicts earthquakes, which coincide with areas where ___________. a. volcanoes also regularly occur b. movements of the crust take place c. rocks break and move d. All of the above are correct.

By deep-sea drilling, the Glomar Challenger proved the theory that if the model of sea-floor spreading was correct, then sea-floor sediment should be ____________ and ____________ as one moves away from the spreading axis. a. thinner; younger b. thinner; older c. thicker; older d. thicker; younger

Distinctive rock sequences on South America terminate at the Atlantic Ocean but reappear on the continent of ____________. a. Africa b. Australia c. Europe d. North America

Marine magnetic anomaly belts run parallel to ____________. a. continental coastlines b. mid-ocean ridges c. continental shelves d. fracture zones

Evidence for a united Pangaea comes from the fossil record of which type(s) of organisms? a. plants b. large terrestrial animals c. freshwater animals d. All of the above are correct.

According to the figure below, the Earth's magnetic reversals are likely due to ______________. a. lightning strikes b. changes in circulation patterns in the outer core c. meteorite impacts d. changes in circulation patterns in the inner core

Marine magnetic anomalies result from sea-floor spreading in conjunction with ____________. a. magnetic storms on the surface of the Sun b. global warming c. magnetic polarity reversals d. apparent wander of the magnetic poles

According to the figure below, Earth's magnetic poles move constantly, but don't seem to stray farther than about ____________ from the geographic poles. a. 500 km b. 1,000 km c. 1,500 km d. 2,000 km

Which plant genus dominated glaciated regions during the Late Paleozoic and Early Mesozoic? a. Neuropteris b. Glossopteris c. Quercas d. Ginkgo

The magnetic field of Earth in the geologic past is ____________. a. known to have experienced numerous polarity reversals, due to remnant magnetization of iron-rich minerals in rocks b. known to have been constant through geologic time, due to remnant magnetization of iron-rich minerals in rocks c. known to have been constant through time, on the basis of theoretical calculations d. unknown, but it is assumed to have been identical to today's

The discovery that each continent had different and separate polar wander paths proved that _____________. a. both the poles and continents move b. the poles move c. Wegener was right: continents move

Within the sea floor, the rate of geothermal heat flow is greatest ____________. a. at the edges of ocean basins b. along mid-ocean ridges c. along fracture zones d. in the center of abyssal plains

Wegener's idea of continental drift was rejected by American geologists because ____________. a. his English was too poor to be understood by them b. he had relatively little evidence supporting the existence of a supercontinent c. he could not conceive of a valid mechanism that would cause continents to shift positions d. the apparent fit of continental coastlines is blurred when the margins are defined by the edges of continental shelves rather than sea level

Where Earth's magnetic dipole intersects with the surface of the planet is called the ___________. a. geographic pole b. magnetic dipole c. magnetic inclination d. magnetic pole

Late Paleozoic glacial deposits are NOT found in which of the following places? a. India b. South America c. North America d. southern Africa

Consult the figure below. Abundant swamps led to the formation of coal during the Late Paleozoic in which of the following places? a. southern Africa b. India c. South America d. North America

Evidence that glaciers once covered an area might include ______________. a. backwash and grabens b. backwash and striations c. till and striations d. till and grabens

According to Wegener, puzzle pieces are to a jigsaw puzzle as ____________ is/are to Pangaea. a. plate tectonics b. sea-floor spreading c. continental drift d. continents

Wegener's evidence for a united Pangaea was so compelling that virtually all geologists agreed with the idea of continental drift during his lifetime. a. true b. false

Beneath a blanket of sediments, oceanic crust is primarily composed of two rocks, ____________ and ____________. a. gabbro; basalt b. granite; diorite c. sandstone; shale d. slate; gneiss

Consult the figure below. Marine magnetic anomaly belts are widest when and where ____________. a. sea-floor spreading rates are relatively slow b. sea-floor spreading rates are relatively rapid c. continents are joined to form supercontinents

Without plate tectonics, we would not have _______________. a. plates in constant motion b. mountain building c. formation of new oceans d. All of the above are correct.