Chapter 17 - Plate Tectonics Review

ocean ridges

Features found at divergent boundaries include

boundaries

Tectonic plates interact at places called plate

reversed polarity

A field that is opposite the present field has _______.

normal polarity

A field with the same orientation as today's field is said to have

rift valley

A long, narrow, fault-bounded, continental depression

Slab pull

A process that occurs at convergent boundaries

transform boundary

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

continental rocks containing these fossils had once been joined

Based on observations of fossils of Glossopteris, Wegener concluded that

landmasses drifted away from the south pole

Based on the glacial deposits he observed, Wegener argued that

once located closer to the equator

Coal beds in Antarctica indicated to Wegener that this continent was

younger

Compared to ocean crust near deep-sea trenches, crust near ocean ridges is

type of crust involved

Convergent boundaries are classified according to the

transform

Crust is neither created or destroyed along which of the following boundaries?

magnetometer

Device used to map the ocean floor that detects small changes in magnetic fields.

new ocean crust

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

magnetic field

Earth's ____ has changed over time.

subduction zones

Forms when two oceanic plates converge

land-dwelling animals

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

probably did not cross the oceans

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

youngest near ocean ridges

Isochron maps of the seafloor indicate that ocean crust is

matching coastlines

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

True

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

couldn't explain how or why the continents moved

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

all of Earth's continents

Pangaea was an ancient supercontinent made up of

divergent boundaries

Places where plates are pulling apart

convergent boundaries

Places where tectonic plates are coming together

Transform boundaries

Places where tectonic plates slide along beside one another as they move

a deep-sea trench

Subduction results in the formation of

divergent boundary

The Mid-Atlantic Ridge is an example of a

mantle

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

a mirror image of that of the other side

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

Pangaea

The name of the single landmass that broke apart 200 million years ago and gave rise to today's continents

seafloor spreading

The theory that explains how new ocean crust is formed at ocean ridges and destroyed at deep-sea trenches

convection

The transfer of thermal energy by the movement of heated matter is

magnetic field data

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

False

True or False. Deep-sea trenches are vast, underwater mountain chains.

True

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

False

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

True

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

False

True or False. The magnetic patters 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 the ocean ridges.

continental drift

Wegener's hypothesis that all continents were once connected in a single large landmass that broke apart about 200 million years ago and drifted slowly to their current positions

Melted magma erupts and forms an arc of islands

What can happen when two oceanic plates converge and one is subducted into the mantle?

New ocean crust forms

What happens along a divergent boundary?

A trench and a mountain range with many volcanoes form

What happens when an oceanic plate converges with a continental plate?

on the seafloor

Where are most divergent boundaries found?

a mountain range

Which feature is associated with a continental-continental late boundaries?

volcanoes

Which of the following is NOT associated with transform boundaries.

a rift valley

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

plate tectonics

Which theory states that Earth's crust and rigid upper mantle move in different directions and at different times over Earth's surface?

magnetic reversal

a switch in the direction of Earth's magnetic field so that the magnetic north pole becomes the magnetic south pole and the magnetic south pole becomes the magnetic north pole.

Subduction

occurs when one tectonic late descends beneath another

theory of plate tectonics

states that Earth's crust and rigid upper mantle are broken into enormous slabs called plates that slowly move over Earth's surface

Ridge push

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