Module 13

True or False: Rock samples taken near ocean ridges are older than rock samples taken near deep-sea trenches

False

Earth's continents were once joined as a single landmass called

Pangaea

Subduction results in the formation of

a deep-sea trench.

At which tectonic plate boundary do plates slide horizontally past each other?

transform boundary

Convergent boundaries are classified according to the

type of crust involved.

Which of the following best describes what happens when an oceanic plate converges with a continental plate?

A trench and a mountain range with many volcanoes can form.

German meteorologist __________________ was the first to propose a scientific hypothesis about the movement of continents.

Alfred Wegener

Rock layers that were once likely joined and then separated as continents drifted apart include those in North America and ______.

Europe Greenland

True or False: The thickness of ocean-floor sediments decreases with distance from an ocean ridge.

False

How does fossil evidence support the hypothesis of continental drift?

Fossils of the same land-dwelling animals have been found on widely separated continents.

What occurs during convection?

Thermal energy is transferred by the movement of heated material from one place to another.

True or False: Earthquake activity and volcanism are common along ocean ridges.

True

True or False: Maps made from sonar and magnetometer data led to the discovery of ocean ridges and deep-sea trenches.

True

True or False: Sonar uses sound waves to measure water depth.

True

True or False: The magnetic patterns on either side of a deep-sea trench are mirror images of each other.

True

True or False: The theory of seafloor spreading explains that Earth's continents move because they ride atop ocean crust as it moves away from ocean ridges.

True

True or false: Scientists do not fully understand the force or forces that cause tectonic plates to move.

True

Continental drift was not widely accepted when it was first proposed because

Wegener couldn't explain why or how the continents moved.

Which question has remained unanswered since Wegener first proposed continental drift?

What force causes tectonic plates to move?

The magnetic pattern of ocean-floor rocks on one side of an ocean ridge is

a mirror image of that of the other side.

Which of the following landforms results from divergence of continental crust?

a rift valley

Wegener's hypothesis of _________stated that Earth's continents had once been joined as a single landmass.

continental drift

Which hypothesis states that Earth's continents were once joined as a single landmass that broke apart and sent the continents adrift?

continental drift

Based on observations of fossils of Glossopteris, Wegener concluded that

continental rocks containing these fossils had once been joined

What mechanism is believed to drive the movement of tectonic plates?

convection currents in Earth's mantle

Most scientists at the time rejected Wegener's hypothesis of continental drift because he

couldn't explain how or why the continents moved.

The Mid-Atlantic Ridge is an example of a

divergent boundary.

which direction does cool material move?

down

Was constructed from data gathered from continental basalt flows

geomagnetic time scale

Minerals containing this act like small compass needles and record the orientation of Earth's magnetic field at the time of their formation

iron

This type of line connects points on a map that have the same age

isochron

Fossil evidence that supported Wegener's idea of continental drift included

land-dwelling animals.

Based on the glacial deposits he observed, Wegener argued that

landmasses drifted away from the South Pole

To support his hypothesis of continental drift, Alfred Wegener did NOT use

magnetic field data

A change in Earth's magnetic field is called a(n)

magnetic reversal

Device that can detect small changes in magnetic fields

magnetometer

detects small changes in Earth's magnetic field.

magnetometer

The driving forces of tectonic plates are related to convection currents in Earth's

mantle.

Early mapmakers thought continents might have moved based on their observations of

matching coastlines

Many early mapmakers thought Earth's continents had moved based on

matching coastlines.

Each cycle of spreading and magma intrusion along an ocean ridge results in the formation of this

new ocean crust

Each cycle of spreading and intrusion of magma during seafloor spreading results in

new ocean crust.

Features found at divergent boundaries include

ocean ridges.

Where are most divergent boundaries found?

on the seafloor

Coal beds in Antarctica indicated to Wegener that this continent was

once located closer to the equator.

Fossils of aquatic reptiles found in freshwater rocks suggested to Wegener that these reptiles

probably did not cross the oceans.

What is the source of thermal energy for convection in Earth's mantle?

radioactive decay

Which tectonic process associated with convection currents in Earth's mantle occurs when the weight of an elevated ridge pushes an oceanic plate toward a subduction zone?

ridge push

a process whereby the weight of an uplifted ocean ridge pushes an oceanic plate toward a subduction zone.

ridge push

A long, narrow, fault-bounded, continental depression is a(n)

rift valley

In addition to the puzzlelike fit of the continents, what evidence did Wegener use to support his continental drift hypothesis?

rock data climate data fossil data

explains how new ocean crust is created at ocean ridges and destroyed in deep-sea trenches.

seafloor spreading

Which tectonic process associated with convection currents in Earth's mantle occurs as the weight of a subducting plate pulls the trailing lithosphere into a subduction zone?

slab pull

a process that occurs at convergent boundaries.

slab pull

occurs when one tectonic plate descends beneath another.

subduction

Which of the following features forms when two oceanic plates converge?

subduction zones

huge pieces of crust and rigid upper mantle that fit together to cover Earth's surface.

tectonic plates

Crust is neither destroyed nor formed along which of the following boundaries?

transform

places where plates slide horizontally past each other.

transform boundaries

Continental-continental plate collisions produce

very tall mountain ranges.

Which is not a force causing plates to move?

volcanism

Which of the following is NOT associated with transform boundaries?

volcanoes

Compared to ocean crust near deep-sea trenches, crust near ocean ridges is Multiple choice question.

younger.

Isochron maps of the seafloor indicate that ocean crust is

youngest near ocean ridges.

What happens along a divergent boundary on the seafloor?

New ocean crust forms.

What is true of ridge push and slab pull?

Ridge push occurs when the weight of the uplifted ridge pushes an oceanic plate toward a subduction zone. Slab pull occurs when weight of the relatively cool, dense subducting plate pulls a trailing slab into a subduction zone.

Pangaea was an ancient supercontinent made up of

all of Earth's continents.

Plates come together at

convergent boundaries

Places where plates move apart

divergent boundaries

A map line connecting points that have the same age is

isochron

The study of Earth's magnetic record is known as

paleomagnetism