Module 6 - The Active Earth: Plate Tectonics

Continental drift

Alfred Wegener's ____ theory hypothesized that Earth's continents were once joined together and later split, and drifted apart.

Changes in the Moon's orbit due to shifting plates

All of the following are evidence supporting the theory of plate tectonics except for ________.

Subduction zones along convergent plate boundaries

Cooler, older, oceanic lithosphere sinks into the mantle at ________.

Hot spot

A very long-lived stationary magma plume located deep in the mantle is called a ________.

Metallic elements

In order to measure the orientation of Earth's magnetic field a rock would need to contain ______.

Centimeters

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

Convergent

The Himalayan Mountain Range is an example of a ____ boundary.

Lithosphere

The _______ includes Earth's crust and the uppermost strong and ridgid part of the mantel.

Ridge push

The downslope sliding of the lithosphere away from a spreading center is called a ____.

Convection

The entire mantle-lithosphere system circulates in large ____ cells.

Rift valley / divergent

The feature created in this diagram is called a ________ and is produced at ________ plate boundaries.

Older

The seafloor and oceanic crust at the Mid-Atlantic Ridge becomes ____ with increasing distance from the ridge axis.

Isostatic adjustment

The weight of an ice sheet can cause the continental lithosphere to sink into the underlying asthenosphere due to ____.

The Mid-Oceanic Ridge is elevated above surrounding seafloor because it is made of hotter and less dense lithosphere than oceanic crust farther away from the divergent boundary.

True or False:

True

True or False: A single plate can carry both oceanic and continental crust.

True

True or False: Continental crust does not normally sink into the mantle because continental crust is of lower density than mantle material.

False

True or False: Continental rifting occurs when two continental plates converge.

True

True or False: The Himalayan Mountains are the tectonic product of a collision between India and Eurasia that began in Eocene time and still continues.

False

True or False: The inner core is molten.

False

True or False: The interior of lithospheric plates are normally tectonically active with occurrences of earthquakes and volcanoes.

True

True or False: The lithosphere floats on the asthenosphere.

True

True or False: The oldest rocks of the oceanic crust are found in deep ocean trenches far away from active, mid-ocean ridges.

False

True or False: The reaction among the scientific community to Wegener's supercontinental theory was very positive.

False

True or False: Young oceanic crust is more dense than older oceanic crust.

The oceanic plate sinks beneath the continental plate and dives into the mantle

When a plate carrying continental crust converges with a plate carrying oceanic crust ____.

Huge mountain ranges

When two continental plates converge, they form ____.

huge mountain ranges

When two continental plates converge, they form ____.

The older, denser plate sinks into the mantle

Where two plates carrying oceanic crust converge ____.

A. continents

Which of the following contains the oldest rocks? A. continents B. seafloors C. spreading centers D. ocean ridges

Fossil records

Which of the following provided evidence for Wegener's theory?

Mid-ocean ridges and rift valleys

Which two features are commonly found at divergent plate boundaries?

Magnetic reversals

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