Chapter 17

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

a rift valley

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 form.

The thickness of ocean sediments that are close to a mid-ocean ridge is __________ the thickness of ocean sediments that are far from mid-ocean ridges.

less than

What is the study of Earth's magnetic record?

paleomagnetism

Wegener proposed that the continents were __________.

plowing through oceanic crust

What can form when two continental plates collide?

Fold Mountains

Where are most divergent boundaries found?

On the SeaFloor

Where do tectonic plates interact?

at plate boundaries

What is the name of Alfred Wegener's hypothesis about moving landmasses?

continental drift

Formed when an ocean basin between converging oceanic and continental plates is entirely subducted.

continental-continental convergent plate boundary

What is thought to be the driving mechanism of plate movement?

convection currents in the mantle

Why did Wegener think that the Antarctic continent had been closer to the equator in the geologic past?

existence of coal beds

What evidence did Wegener use to estimate the time of Pangaea's break up?

fossil data

When a divergent plate boundary forms on continents, a __________ forms.

rift valley

Which type of information was NOT collected by Wegener to support his continental drift hypothesis?

seafloor magnetic data

How are the convection currents set in motion?

slab push and ridge pull

The __________ states that Earth's crust and ridged upper mantle are broken into plates that move at different rates and in different directions.

theory of plate tectonics

Convergent boundaries are classified according to the what? Name the types.

type of crust involved. ocean-ocean, ocean-continental, continental-continental

Rocks close to mid-ocean ridges are __________ rocks far from mid-ocean ridges.

younger than

Harry Hess' theory of __________ explained how ocean crust is generated and destroyed.

Seafloor Spreading

A place where two plates slide laterally past each other is called a __________.

Transform Boundary

What two topographic features of the ocean floor were discovered only with the use of sonar?

mid-ocean ridges and deep-sea trenches