Exam 6: The Active Earth: Plate Tectonics

Oceanic crust is thicker than continental crust.

The San Andreas Fault is an example of a/an __________ plate boundary.

The Mid-Atlantic Ridge is a leg of the Mid-Oceanic Ridge system that divides the Atlantic Ocean.

A portion of a plate with continental crust composing its uppermost layer is thicker than one bearing __________ crust.

A divergent plate boundary is also called a/an __________ __________ or a/an __________ __________.

Continental crust is composed mainly of:

A mantle plume is a vertical column of plastic rock rising from the mantle.

The first supercontinent formed by collisions of microcontinents and island arcs probably about __________ years ago.

The lithosphere floats on the asthenosphere.

The Mid-Oceanic Ridge forms along transform plate boundaries.

The Hawaiian Islands are an example of:

The __________ __________ system is an undersea mountain chain encircling the planet that forms at divergent plate boundaries.

The asthenosphere extends from a depth of about __________ km down to a depth of about __________ km below the surface of the Earth.

Tectonic plates typically move at rates of 1 to 16 __________ per year.

Magnetic orientation that is the same as that of the Earth's current magnetic field is known as __________ __________ __________.

According to the theory of isostasy, the __________ is in floating equilibrium on the __________.

The __________ includes Earth's crust and the uppermost strong and rigid part of the mantle.

The entire mantle-lithosphere system circulates in great __________ cells.

At a divergent boundary between spreading tectonic plates in oceanic crust:

__________ have occurred on average every 500,000 years over the past 65 million years of Earth's history.