Chapter 2 Mastering Geology

Which of the following is a layer of the Earth that is classified NOT by composition, but by physical properties? Core Mantle Geosphere Asthenosphere Crust

-Asthenosphere

In the mid-20th century, researchers dredging the seafloor could not find any materials older than ________.

180 million years

A typical rate of seafloor spreading in the Atlantic Ocean is ________.

2 centimeters per year

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.

______ is a feature of a divergent plate boundary.

An oceanic ridge A rift valley

describes Wegener's idea of continental drift?

Continents were formerly in different positions on the Earth and have shifted to their present locations over time.

What generates the heat necessary for convection in the Earth?

Decay of radioactive materials

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

Divergent

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

Earth's magnetic field switches polarity at irregular time intervals.

The earthquakes that occur in Southern California generally occur along a

Fault

How was the fossil record of ancient life used to support Wegener's hypothesis about Pangaea?

Fossils of identical organisms were found on several continents, indicating the continents were once joined.

____ is an example of a feature associated with an oceanic-continental convergent plate boundary?

The Cascade Mountain Range

How is the thickness of the lithosphere going to change as it moves away from a divergent plate boundary?

Lithosphere will thicken as more mantle is added.

What is the main material being subducted at an ocean-continent convergent boundary?

Oceanic lithosphere

____ is an example of a transform plate boundary

The San Andreas Fault

Which statement about the theory of plate tectonics is correct?

The rigid lithosphere plates overlay the hotter and weaker asthenosphere.

Which of the following pieces of evidence supports the plate tectonic theory? Ocean-floor sediments are thickest at the ridge crest. The polar wandering paths of Europe show that the magnetic north pole has migrated from near Hawaii to its current position over the Arctic Ocean. The stripe patterns of high- and low-intensity magnetism are the same on both sides of an oceanic ridge. The sea floor is oldest at the ridge crest. The volcanoes that make up the Hawaiian Island chain are the same age.

The stripe patterns of high- and low-intensity magnetism are the same on both sides of an oceanic ridge.

Why are volcanoes NOT found at transform boundaries?

Transform boundaries do not cause changes to the pressure, temperature, or composition of the mantle.

Late Paleozoic sedimentary rocks often contain extensive coal seams that were used to support the existence of Pangaea. What would the climate have been at that time and at the location where the coal deposits were formed, and what would it indicate about the continent's past latitude?

Warm, humid climate near the Equator

Why are the mid-ocean ridges higher in elevation than the surrounding ocean floor?

Warmer material near the ridge is less dense, so floats higher on the mantle

Which feature of Wegener's idea of continental drift contributed to its rejection by the scientific community?

Wegener proposed that gravitational forces from the Sun and Moon could move continents.

How will the age and temperature of the subducting plate affect its angle of descent?

Younger and warmer plates will have a shallow angle of descent

The East African rift is a divergent plate boundary that is splitting the continent of Africa into two pieces. What will eventually form around this divergent boundary?

an ocean

Australia is composed of relatively old and thick_______

continental crust

In general, where do earthquakes AND volcanic eruptions occur

divergent plate boundaries

How do plates move at divergent plate boundaries?

Plates move apart.

How do plates move at convergent plate boundaries?

Plates move toward one another.

How do plates move at transform plate boundaries?

Plates slide past one another.

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

SeaFloor Crust

Which of the following rock types is most abundant on Earth's land surface?

Sedimentary rocks

What evidence supports that the glaciers on the southern continents were once part of a single, massive ice sheet?

Striations

What forms at divergent plate boundaries?

new oceanic lithosphere

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

on both sides of the mid-ocean ridge

In general, where do volcanoes form in subduction zones?

on the overriding plate, away form the convergent boundary

Oceanic lithosphere contains oceanic crust and the __________.

outermost part of mantle beneath the oceanic 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

measure the rate of plate motion?

GPS satellites The age of the sea floor

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

Hot spot

What are two differences between oceanic crust and continental crust?

The continental crust is thicker and less dense than oceanic crust.

When matching up once-joined continents such as South America and Africa, the coastlines do not fit together as nicely as the continental shelves. Why might this be the case?

The continental shelves are the edges of the continent. The shoreline simply shows where the sea level is in relation to topography.

Which war was indirectly responsible for the development of the more modern tools that made the theory of Plate Tectonics possible?

World War II