Plate Tectonics

The geological creature on the ocean floor in this region resulted from__

Rising convection currents in the magma

What causes the seafloor to spread?

Rising molten magma

Harry Hess' Theory of ____ explained how ocean crust is created and destroyed.

Seafloor spreading

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

Subduction

How are the convection currents set in motion?

Slab push and ridge pull

Earthquakes focus point is most likely to occur

Along the west coast of North America

The subduction of an oceanic plate beneath a continental plate produces a ___

Chain of volcanic mountains

What was Earth's magnetic polarity like 5 million years ago?

Reverse of today

What was the polarity of the Earth 4 million years ago, according to the figure?

Reversed

Much of Earth's internal heat comes from___

The decay of radioactive elements

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

mid-ocean ridges and deep-sea trenches

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

Divergent boundaries

When a divergent plate boundary forms on continents, a ___ forms

Rift valley

What is isochron?

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

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

A normal polarity

Where are the youngest rocks on the seafloor located?

At the mid-ocean ridges

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

Continental drift

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

Convection currents in the mantle

Identify the subduction zone in the figure.

D

What boundary is between the Americas and Africa?

Divergent

Wegener proposed that continents were ____

Formed at mid-ocean ridges

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

Fossil data

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 has moved

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

It was a time of a giant global ocean

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

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

Magnetite

A device that can detect changes in the strength of the magnetic field.

Magnetometer

What is the study of Earth's magnetic record?

Paleomagnetism

The super continent from Wegener's theory of continental drift is called ___

Pangaea

Where do tectonic plate interact?

Plate boundaries

The tremendous amount of heat within Earth powers

Plate tectonics

The ___ states that Earths crust and ridged upper mantle are broken into places 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

Probability that it came from a time when the magnetic field is the same as today.

Very likely

Rocks close to mid-ocean ridges are __ rocks far from mid-ocean ridges

Younger than