Oceanus BQ 2

If two oceanic plates collide and one is older and cooler (and therefore, denser) than the other, what will happen?

A deep trench will form.

The Hawai'ian Islands formed as they pass over a hot spot in the middle of the ____.

Pacific Plate

Earlier than 200 million years ago, the continents were joined into one supercontinent called ____.

Pangaea

The hot, partially melted, slowly flowing layer of Earth is called the ____.

asthenosphere

The Himalayan Mountains were formed as a result of ____.

continent-continent convergence

The rigid outer layer of Earth that comprises the continental crust, oceanic crust, and the uppermost mantle is called the ____.

lithosphere

The ____ accounts for 83 percent of Earth's volume.

mantle

Japan is located along the "Pacific Ring of Fire" and experiences many earthquakes. The majority of the earthquakes around Japan occur ____.

only on the east side of the island where the Pacific plate subducts

What are the primary elements in Earth's continental crust?

oxygen, silicon, and aluminum

The magnetic striping of the seafloor is considered evidence of seafloor spreading and ____.

periodic reversals in the polarity of Earth's magnetic field

A boundary in which crustal plates slide laterally past one another is called a ____.

transform fault

California's San Andreas fault is which type of plate boundary?

transform plate boundary

Scientists believe the breakup of Pangaea occurred about ____.

200 million years ago

About how many kilometers (miles) is it from the center of Earth to the crust?

6,370 kilometers (3,980 miles)

The largest known mantle plume is located beneath ____.

Africa

As early as the 1700s, scientists and observers noticed a remarkable coincidence of shape of the Atlantic coasts of Africa and ____.

South America

What is the primary reason for the inside of Earth being hot?

The decay of radioactive elements is creating heat in Earth's inner layers.

Roughly how fast do most lithospheric plates move?

about 5 centimeters per year

The mid-ocean ridges are ____.

divergent plate boundaries

A cross section of Earth reveals a layered structure that has different thicknesses and densities. How do geologists know this?

from observing the transit times through Earth of seismic waves generated by earthquakes