Earth Science - Chapter 17

How are the convection currents set in motion?

Slab push and ridge pull

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

Fossil data

Where do tectonic plates interact?

At plate boundaries

The supercontinent from Wegener's theory of continental drift is called __________

Pangaea

The tremendous amount of heat within Earth powers _________

Plate tectonics

An expedition finds a sample in the rock on the seafloor thought to be 4 million years old. What was the polarity of the Earth at that time, according to the figure?

Reversed

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

Rift valley

The geologic features on the ocean floor in this region resulted from _______

Rising convection currents in the magma

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

Convection currents in the mantle

According to the data shown in the figure, what was Earth's magnetic polarity like 5 million years ago?

The reverse of today

Much of Earth's internal heat comes from ___________________

The decay of radioactive elements

What is an isochron?

A line on a seafloor map tat connects points of equal age

What is the study of Earth's magnetic record?

Paleomagnetism

What causes the seafloor to spread?

Rising molten magma

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

Younger than

Where are the youngest rocks on the seafloor located?

At the mid-ocean ridges

The subduction of an oceanic plate beneath a continental plate produces a(n) _________

Chain of volcanic mountains

Wegener proposed that the continents were __________

Formed at mid-ocean ridges

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 polarity of a magnetic field that has the same polarity as the present magnetic field?

A normal polarity

According to the figure, where is an earthquake's focus most likely to occur?

Along the west coast of North America

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

Continental drift

Identify the subduction zone in the figure.

D (the figure has label D on it)

The map shows where the continents are likely to move in the next 50 million years. The shaded area represents their present position. According to the data on this map, what kind of boundary is found between the Americas and Africa?

Divergent

Places where two tectonic plates are moving away from each other are called __________.

Divergent boundaries

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

Glacial deposits

What was one reason that Wegener's hypothesis of continental drift was rejected?

He could not explain where the continents had moved

During the time of Pangaea, what had the greatest impact on Earth's climate?

It was a time of a giant global ocean

Which mineral may preserve magnetic patterns on the ocean floor which would help support tectonic plates?

Magnetite

__________ is a device that can detect changes in the strength of the magnetic field.

Magnetometer

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

Mid-ocean ridges and deep-sea trenches

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

Seafloor spreading

What is the process called when one plate is forced beneath another at a convergent plate boundary?

Subduction

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

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

Transform boundary

An expedition brings up a piece of rock from the Gauss normal epoch. According to the figure, what is the probability that it came from a time when the magnetic field is the same as today?

Very likely