Name: __________________________  Date: _____________

1.	The major constituents of the Earth's atmosphere are	
A)	95% carbon dioxide and some water vapor.	
B)	methane, ammonia, water vapor, and carbon dioxide in about equal amounts.	
C)	77% oxygen and 21% nitrogen.	
D)	77% nitrogen and 21% oxygen.	

2.	Billions of years ago, the Earth's atmosphere was composed primarily of carbon dioxide. What happened to much of this carbon dioxide?	
A)	It is still in the atmosphere.	
B)	It was dissolved into the Earth's oceans.	
C)	It was broken down into carbon and oxygen by solar ultraviolet light.	
D)	It was lost to space.	

3.	The presence of oxygen in the Earth's atmosphere is thought to result directly from what type of process?	
A)	Volcanic eruptions	
B)	Out-gassing of the oceans	
C)	The original condensation of interplanetary gas clouds	
D)	Biological activity of plants and animals	

4.	An “ozone hole” is	
A)	a region centered on the equator where ozone levels are always very low because of destruction by the direct sunlight received there.	
B)	a region of the stratosphere above the South Pole where ozone levels occasionally drop to very low levels.	
C)	the name given to small pits or holes on the aluminum surface of an aircraft, etched there by the corrosive ozone encountered in the stratosphere, requiring regular maintenance.	
D)	a permanent region of very low ozone content in the stratosphere centered over the south pole that has been there for thousands of years, the resulting transparency to UV radiation accounting for the lack of life forms there.	

5.	What is the most important reason why we need the ozone layer above us?	
A)	It protects us from the solar wind.	
B)	It allows long-distance radio communication by reflecting radio waves back to the Earth's surface.	
C)	It shields us from harmful solar ultraviolet radiation.	
D)	It provides a convenient dumping site for chlorofluorocarbon chemicals, which are harmful to life.	

6.	In which layer of the Earth's atmosphere does all of the weather occur?	
A)	The stratosphere	
B)	The mesosphere	
C)	The thermosphere	
D)	The troposphere	

7.	How was the Mid-Atlantic Ridge formed?	
A)	Two crustal plates slid past each other in a transverse fault.	
B)	The weight of sediments caused the ocean floor to sink, and the ridge resulted from slumping toward the center of this basin.	
C)	Molten rock pushed up from the Earth's interior and forced two crustal plates apart.	
D)	Two crustal plates collided, causing one plate to buckle, forming the ridge, while the other plate was thrust down beneath it.	

8.	What is the cause of the great mountain ranges on the Earth, such as the Rockies, the Andes, and the Himalayas?	
A)	The carving of continents during ice ages, the mountains being left behind as “islands” in a sea of glaciers	
B)	Heat from the Earth's interior causing the Earth's crust to expand and then crumple.	
C)	Two tectonic plates being pushed apart by molten rock that is being forced up between them	
D)	A collision of two tectonic plates that are moving at different velocities across the face of the Earth	

9.	On the Earth, the majority of earthquakes occur	
A)	along regions of greatest thermal stress in arctic and antarctic regions.	
B)	in the centers of tectonic plates (e.g., North American continent).	
C)	along the boundaries of major tectonic plates.	
D)	along the zone of maximum tidal stress around the equator.	

10.	The motions of large portions of the Earth's surface, the “plates,” are caused by	
A)	pressure variations in the Earth's atmosphere, both daily and seasonal.	
B)	tidal flow in oceanic waters.	
C)	flexing of the Earth's surface due to solar heating and night-time cooling.	
D)	convective flow of material in the Earth's interior.	

11.	The Earth's mantle, the semi-molten layer below the crust, is composed largely of what chemical materials?	
A)	Iron-poor rocks and minerals	
B)	Almost pure iron	
C)	Solid hydrogen and helium	
D)	Minerals rich in iron and magnesium	

12.	What is believed to be the composition of the Earth's core?	
A)	About 80% iron and 20% lighter elements	
B)	About  iron and  lighter elements	
C)	About  iron and  lighter elements	
D)	Essentially pure iron	

13.	What is the relationship between the mantle and the crust of the Earth?	
A)	The crust sits motionless on top of the mantle and does not interact with it.	
B)	Convection in the mantle moves the continents around, but there is no transfer of material from the mantle to the crust or vice-versa.	
C)	New layers of crust are formed when magma from the mantle flows out over old crust, and this old crust remains as the lowest level of the crust.	
D)	New crust is formed by magma rising from the mantle in some places, and old crust is pushed back down into the mantle in other places.	

14.	The magnetic field of the Earth is caused by	
A)	a solid iron magnet inside the Earth.	
B)	electric currents flowing in the molten core.	
C)	the motion of electrically charged particles in the solar wind blowing around the Earth.	
D)	electric currents flowing in the high atmosphere (ionosphere) of the Earth.	

15.	What causes the phenomenon of the aurora?	
A)	Solar ultraviolet light excites ozone molecules in the ozone layer.	
B)	Charged particles from the magnetosphere strike atoms in the upper atmosphere, causing them to emit characteristic colors of light.	
C)	Light from solar flares reflects from high-altitude clouds in the Earth's atmosphere.	
D)	Charged particles emit light as they spiral along magnetic field lines in the magnetosphere.	

16.	What is the diameter of the Moon compared to that of the Earth?	
A)	About 1/4 of the diameter of the Earth	
B)	Less than 1/100 of the diameter of the Earth	
C)	About 1/10 of the diameter of the Earth	
D)	Just over 1/2 the diameter of the Earth	

17.	Most of the craters on the Moon were formed by	
A)	water erosion, followed by evaporation early in the Moon's history, leaving behind the empty basins, the maria, and craters.	
B)	a nuclear war in which the lunar inhabitants wiped themselves off the face of the Moon.	
C)	bombardment by interplanetary meteoritic material.	
D)	volcanic action, the craters being the old calderas of volcanoes.	

18.	Maria are	
A)	ancient riverbeds, now dry.	
B)	uplifted regions surrounding large volcanoes.	
C)	heavily cratered highland regions.	
D)	ancient lava flood-plains.	

19.	What is the name of a long, winding crack in a lunar mare?	
A)	A rille	
B)	A caldera	
C)	A rift zone	
D)	A regolith	

20.	Most of the mountain ranges on the Moon are	
A)	the result of the build-up of meteoritic dust by winds on the Moon.	
B)	the result of water flow and erosion on the Moon's soft surface.	
C)	the circular edges and rims of large maria that have been formed by impacts from large objects.	
D)	the result of plate tectonic movement, similar to that on the Earth.	

21.	A regolith is	
A)	an extremely large, isolated rock on the surface of a planet or other object.	
B)	a lithospheric plate, moved slowly by geologic processes.	
C)	a heavily cratered region on a planet or other object.	
D)	a layer of pulverized rock on the surface of a planet or other object.	

22.	Water has recently been discovered on the Moon in the form of	
A)	ice in deep craters near the north pole, perpetually shaded from sunlight.	
B)	thin, hazy clouds overlaying the dark polar regions, where they are shaded from the Sun's heat.	
C)	permafrost embedded in the centers of the large, dark maria, their darker color showing the presence of frost.	
D)	fluid water flowing in deep tunnels (some of which have collapsed to form rilles on the lunar surface), where it is protected from solar radiation.	

23.	Which of the following theories is now considered to be the most likely for the formation of our Moon?	
A)	Fission theory, in which a passing planetesimal body pulled material out of the still-molten Earth and left it in orbit to form the present-day Moon	
B)	Co-creation theory, in which the Earth and the Moon were formed at the same time out of the same material	
C)	Capture theory, in which the Earth's gravity drew the Moon into orbit around it	
D)	Collision-ejection theory, where an interplanetary collision knocked material into orbit around the Earth that eventually formed into the present-day Moon	

24.	How many “tidal bulges” are there on the Earth caused by the Moon's gravity?	
A)	One, facing (almost) directly toward the Moon	
B)	One, on the side of the Earth facing away from the Moon	
C)	Two, one facing (almost) directly toward the Moon and one (almost) directly away from the Moon	
D)	Four, one facing (almost) directly toward the Moon and the other three at 90° intervals from this one	

25.	Which of the following describes the dynamics of the Earth-Moon system?	
A)	The Earth's rotation is speeding up, whereas the Moon is moving slowly outward away from the Earth.	
B)	The Earth's rotation is slowing down, whereas the Moon is moving slowly outward away from the Earth.	
C)	The Earth's rotation is speeding up, whereas the Moon is moving slowly toward the Earth.	
D)	The Earth's rotation is slowing down, whereas the Moon is slowly approaching the Earth by spiraling inward.	

Answer Key

1.	D	
2.	B	
3.	D	
4.	B	
5.	C	
6.	D	
7.	C	
8.	D	
9.	C	
10.	D	
11.	D	
12.	D	
13.	D	
14.	B	
15.	B	
16.	A	
17.	C	
18.	D	
19.	A	
20.	C	
21.	D	
22.	A	
23.	D	
24.	C	
25.	B