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