Ch. 6: The Earth

Why isn't the Earth a perfect sphere? A) Rotation causes the equator to bulge out. B) Rotation causes the poles to bulge out. C) The Earth's magnetic field causes the equator to bulge out. D) The Earth is perfectly round.

A) Rotation causes the equator to bulge out.

What is happening when two plates are smashing into one another? A) Subduction causes mountains to be built up; earthquakes and volcanoes may also occur. B) Rifting causes mountains to be built up; earthquakes and volcanoes may also occur. C) Precession causes mountains to be built up; earthquakes and volcanoes may also occur. D) Nothing.

A) Subduction causes mountains to be built up; earthquakes and volcanoes may also occur.

Our knowledge of the composition of the Earth's core comes from A)...analysis of earthquake waves. B)... x-ray pictures taken with a powerful device in Russia. C)...samples obtained by drilling deep holes. D)... analysis of the material erupted from volcanoes. E)... Both (c) and (d).

A)...analysis of earthquake waves.

How do we know the Earth has a liquid core? A) Both S and P waves pass through it. B) S waves pass through it, but P waves do not. C) P waves pass through it, but S waves do not. D) Because we have used X-rays to probe it.

B) S waves pass through it, but P waves do not.

Why is the inner core solid even though it is hotter than the outer liquid core? A) This is not unusual: hotter things tend to be more solid. B) The great pressure at Earth's center forces the atoms in the core together, causing it to solidify. C) Radioactivity cause liquid materials to become solid. D) The dynamo effect causes ions in the Earth's interior to become solid.

B) The great pressure at Earth's center forces the atoms in the core together, causing it to solidify.

Currents in the Earth's molten iron core create the planet's magnetic field. These current are probably caused by A) rotational motion and radioactivity. B) rotational motion and convection. C) radioactivity and convection. D) rifting and subduction.

B) rotational motion and convection.

The interior of the Earth is very hot because of _______. A) fusion reactions B) the radioactive decay of elements C) oxidation D) internal combustion

B) the radioactive decay of elements

The ozone layer protects us from A) infrared radiation. B) ultraviolet radiation. C) gamma rays. D) cosmic rays.

B) ultraviolet radiation.

About how hot is the core of the Earth? A) 15 million K. B) 15,000 K. C) 6500 K. D) 300 K.

C) 6500 K.

How is the age of the Earth measured? A) By counting tree rings. B) By analyzing the strength of the Earth's magnetic field. C) By studying the ratios of radioactive materials in rocks. D) By measuring the amount of heat the planet emits into space.

C) By studying the ratios of radioactive materials in rocks.

On what plate of the crust is North America located? Which way is it moving? A) Pacific; East. B) Pacific; West. C) North American; East. D) North American; West.

C) North American; East.

What are the most common elements composing the Earth? A) Hydrogen and helium. B) Carbon and nitrogen. C) Oxygen and silicon. D) Uranium and plutonium.

C) Oxygen and silicon.

If the shape of the Earth's orbit was unaltered but its rotation axis was shifted so that it had no tilt with respect to the orbit, seasons would be A)... essentially as they are now. B)... more extreme, with colder winters and hotter summers. C)...essentially nonexistent, with little temperature change at a given place throughout the year. D)... Not enough information is given to make a reasonable guess. E)... Either (a) or (b) is most likely.

C)...essentially nonexistent, with little temperature change at a given place throughout the year.

What does the Greenhouse Effect cause? A) It shields us from the Sun's ultraviolet rays. B) It causes the Earth's surface and atmosphere to be warmer than they would be otherwise. C) It is the main source of the Earth's oxygen. D) All of the above

D) All of the above

How are the auroras related to the Earth's magnetic field? A) The Earth's magnetic field "channels" solar particles toward our poles, so that is where auroras are most common. B) Auroras are a glow of the magnetic field caused by its vibration. C) Solar particles directed into our atmosphere by the Earth's magnetic field excite atoms in our upper atmosphere. These atoms then emit light, which we see as auroras. D) Both A and C

D) Both A and C

What are the main constituents of the Earth's atmosphere? A) Carbon dioxide and water vapor. B) Hydrogen and helium. C) Methane and ozone. D) Nitrogen and oxygen.

D) Nitrogen and oxygen.

The shifting of large blocks of the Earth's surface is usually referred to today as what? A) The Dynamo Effect. B) Continental Drift. C) The Corilolis Effect. D) Plate Tectonics.

D) Plate Tectonics.

What evidence indicates that part of the Earth's interior is liquid? A)...With sensitive microphones, sloshing sounds can be heard. B)... We know the core is lead, and we know the core's temperature is far above lead's melting point. C)... Deep bore holes have brought up liquid from a depth of about 4000 kilometers. D)... No S type of seismic waves are detectable at some locations after an earthquake. E)... S type of waves are especially pronounced at all locations around the Earth after an earthquake.

D)... No S type of seismic waves are detectable at some locations after an earthquake.

The slow shifts of our planet's crust are believed to arise from A)... the gravitational force of the Moon pulling on the crust. B)... the gravitational force of the Sun pulling on our planet's crust. C)... the Earth's magnetic field drawing iron in crustal rocks toward the poles. D)... heat from the interior causing convective motion, which pushes on the crust. E)...the great weight of mountain ranges forcing the crust down and outward from their bases.

D)... heat from the interior causing convective motion, which pushes on the crust.

Scientists think the Earth's core is composed mainly of A).. silicate rocks. B).. uranium. C).. lead. D)..iron. E)..sulfur.

D)..iron.