OCE1001 - Chapter 3

Subduction zones are areas where new seafloor is created. True False

False

A cross section of Earth reveals a layered structure that has different thicknesses and densities. How do geologists know this? From comparisons with drill cores taken by robot spacecraft on Mars and Venus From observing the transit times through Earth of waves generated by earthquakes From drilling and digging down into the various layers From observing the characteristics of lava and gas issuing from volcanic vents

From observing the transit times through Earth of waves generated by earthquakes

If two oceanic plates collide and one is older and cooler (therefore more dense) than the other, what will happen? A deep trench will form. A mid-ocean ridge will form. Continental mountains will form. A hot spot will form.

A deep trench will form.

Which statement with regard to hot spots is true? Hot spots are always located along plate boundaries. Hot spots are relatively stationary features. Hot spots can only exist beneath oceanic crust. The Aleutian Islands in Alaska formed due to a hot spot.

Hot spots are relatively stationary features.

The Hawaiian Islands formed as they pass over a hot spot in the middle of the ____. Pacific Plate Mariana Trench Nazca Plate Mid-Atlantic ridge

Pacific Plate

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

Pangaea

One piece of evidence that suggests the existence of Pangaea is the discovery of Mesosaurus fossils in Argentina and Africa, but nowhere else. True False

True

The oceanic crust is primarily made of basalt. True False

True

The Himalayan Mountains were formed as a result of ____. continent-continent divergence continent-continent convergence ocean-continent divergence ocean-continent convergence

continent-continent convergence

A "mystery" in our understanding of plate tectonics has been, until recently, the nature of the power source capable of moving the plates and the continents embedded within them. Recent evidence indicates the power source to be ____. the action of ocean currents is dragging along the seafloor, causing the seafloor and the continents to move convection currents within Earth's mantle is moving the plates the continual vibration from earthquakes and volcanoes slowly moves the continents equator-ward under the influence of centrifugal force the readjustment of the surface to continual shrinking of the whole Earth

convection currents within Earth's mantle is moving the plates

The rigid outer layer of Earth that comprises both continental and oceanic crust is called the ____. lithosphere asthenosphere outer core hydrosphere

lithosphere

The ____ accounts for 83% of Earth's volume. crust inner core mantle outer core

mantle

Japan is located along the Pacific Ring of Fire and experiences many earthquakes. Almost all of the earthquakes around Japan occur ____. only on the east side of the island where the Pacific plate subducts near the Pacific spreading center only on the west side of the island where the Eurasian plate subducts near the Mid-Atlantic ridge

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

The magnetic striping of the seafloor is considered evidence of seafloor spreading and ____. periodic interruptions in mantle convection subduction occurring in rift valleys changes in Earth's axis of rotation periodic reversals in the polarity of Earth's magnetic field

periodic reversals in the polarity of Earth's magnetic field

California's San Andreas fault is which type of plate boundary? ocean-continent convergent plate boundary continent-continent convergent plate boundary transform plate boundary divergent plate boundary

transform plate boundary

About how many kilometers (miles) is it from the center of Earth to the outer edge of the outer core? 2,880 kilometers (1,800 miles) 1,264 kilometers (790 miles) 12,523 kilometers (7,827 miles) 6,370 kilometers (3,980 miles)

6,370 kilometers (3,980 miles)

Convection within the inner core facilitates continental drift. True False

False

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

South America

What is the primary reason for the inside of Earth being hot? A nuclear process like that found in stars is at work in Earth's interior. Huge quantities of oil and natural gas occasionally burn deep within Earth. No heat is being generated, but Earth's outer layers have prevented the escape of heat trapped during the planet's initial formation. The decay of radioactive elements is creating heat in Earth's inner layers.

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

Which statement is true with regard to subduction zones? They are sites where lithospheric plates are diverging or pulling apart. They are marked by the presence of mid-ocean ridges. They are zones where old seafloor descends into the crust and mantle. They are also referred to as "hot spots."

They are zones where old seafloor descends into the crust and mantle.

Roughly how fast do most lithospheric plates move? about 5 kilometers per year about 5 centimeters per hour about 5 centimeters per year about 5 kilometers per thousand years

about 5 centimeters per year

Buoyancy is the ability of an object to float in a fluid by ____. displacing a volume of water which weighs slightly less than its own weight displacing a volume of water equal in weight to its own weight weighing less than the water surrounding it displacing a volume of water which weighs slightly more than its own weight

displacing a volume of water equal in weight to its own weight

The mid-ocean ridges are ____. convergent plate boundaries transform or lateral plate boundaries divergent plate boundaries subduction zones

divergent plate boundaries