1. Plate Tectonics

What percentage of earthquakes occurs at active plate boundaries?

95%

How are normal polarity and reverse polarity of Earth's magnetic field different?

A compass points toward the North Pole during normal polarity and to the South Pole during reverse polarity.

In general, what is our best evidence that the orientation of Earth's magnetic field has changed over time?

A record of Earth's magnetic field is recorded in oceanic rocks, which show a clear pattern of changes in Earth's magnetic polarity.

A cross-section through a plate boundary shows earthquakes in groups at shallow, intermediate, and deep locations descending at an angle away from the boundary. What feature do these earthquakes delineate?

A subducting oceanic lithospheric plate

Continued movement of the continental crust on the west side of the San Andreas fault could result in which of the following features?

An island

In studies of rock obtained from ocean basins all over Earth, the oldest ages obtained are approximately 200 million years before the present. Why have no older oceanic rocks been discovered?

Due to tectonic activity, rocks on the ocean floor are continually recycled.

Which of the following statements about Earth's magnetic field is most accurate?

Earth's magnetic field switches polarity at irregular time intervals

How do reversals in the Earth's magnetic field support plate tectonic theory?

Mirror images of matching magnetic reversals in oceanic crust generated at spreading centers

Which of the following statements regarding transform plate boundaries is not correct?

New oceanic crust is formed at transform plate boundaries.

Which of the following regions was not part of the large Southern Hemisphere continent of Gondwana?

North America

Which of the following techniques can be used to recreate the configuration of supercontinents that existed before Pangaea?

apparently wandering polar paths

Australia is composed of relatively old and thick .

continental crust

What geologic process initiated the breakup of Pangaea approximately 165 million years ago?

continental rifting

How often does the Earth's magnetic field switch polarity?

every 100,000 to several million years

The earthquakes that occur in Southern California generally occur along a

fault

Which of the following processes can be observed at the margins of lithospheric plates?

faulting, earthquakes, volcanoes, and mountain building.

Old Faithful Geyser at Yellowstone National Park in the United States acquires its energy from a

hot spot

Where would you expect to see alternating bands of rock with different magnetic polarities?

on both sides of the mid-ocean ridge

Intervals of paleomagnetic ___________ is/are characterized by the alignment of the magnetic south pole and the geographic north pole.

reversed polarity

found in the Atlantic Ocean between North America and Europe is composed of dense and relatively young rock.

seafloor crust

The slowly increasing distance between South America and Africa is due to

seafloor spreading

Layered exposed by erosion can be seen when looking at the Grand Canyon in the United States.

sedimentary rock

The extremely deep ocean Marianas Trench is a result of .

subduction

Which of the following lithospheric plates is not included among the seven largest?

the Philippine plate

The timing of plate tectonic motions can be calculated by all of the following except __________.

the maximum depth of earthquakes at a subduction zone

Earth's lithospheric plates are composed of crust and which of the following layers?

the outermost portion of the mantle

What type of plate boundary forms where two plates slide past one another horizontally?

transform

Which of the following geologic processes and/or phenomena is not found at transform plate boundaries?

volcanoes

Would NOT be found at a divergent boundary

volcanoes producing andesitic lavas thrust faults

Would be found at a divergent boundary

volcanoes producing mafic lavas normal faults

Since the breakup of Pangaea approximately 165 million years ago, a new supercontinent cycle has begun with the collision of which of the following continents?

India and Asia

Currently the Juan de Fuca plate is interacting with the North American plate where inland volcanoes and deep focus earthquakes are occurring. What type of plate boundary is this?

a convergent plate boundary

Which type of plate boundary is most closely associated with the formation of new ocean floor?

a divergent