Deck 7: Earth and the Moon

Question 1

The basic color(s) of Earth as seen from outer space (see Figure 7-1 in the text) is (are)

A) brown.
B) blue, white, and brown.
C) green and brown.
D) gray and white.

Answer 1

blue, white, and brown.

Question 2

One of the major differences between Earth and its neighboring planets Venus and Mars is the lack of large quantities of CO₂ in its atmosphere. If all three planets were originally formed with significant quantities of this gas in their atmospheres, where is the majority of this CO₂ on Earth at the present time?

A) dissociated by UV and visible sunlight into carbon and oxygen that now exists in abundance as separate chemicals
B) concentrated high in the atmosphere where it contributes to the greenhouse effect
C) dissolved in seawater, a situation that cannot arise on the neighboring planets
D) locked up in carbonate and carbon-rich rocks and minerals formed in the sea and on Earth's surface

Answer 2

locked up in carbonate and carbon-rich rocks and minerals formed in the sea and on Earth's surface

Question 3

What percentage of the sunlight that falls on Earth is reflected into space?

A) almost 100% because of the significant cloud cover
B) 31%
C) almost none-most of the energy is absorbed to maintain the present surface temperature of Earth
D) 69%

Answer 3

31%

Question 4

"It has a cool, solid surface with an atmosphere of nitrogen and oxygen and clouds of water vapor." Which of the planets fits this description?

A) Mars
B) Mercury
C) Venus
D) Earth

Question 5

Which is the MOST abundant gas in Earth's atmosphere?

A) oxygen
B) nitrogen
C) hydrogen
D) carbon dioxide

Question 6

How does Earth's albedo compare with those of Mars and Venus?

A) All terrestrial planets have about the same albedo.
B) Earth has the highest albedo of the three.
C) Earth has the lowest albedo of the three.
D) Earth's albedo is less than that of Venus but greater than that of Mars.

Question 7

Earth's "albedo" is the fraction of radiant energy from the Sun that Earth re-radiates into space. This number

A) is constant; it does not vary on a daily or seasonal basis.
B) varies as Earth rotates, but the daily variation does not change with the seasons.
C) varies with the seasons but is constant during any 24-hour rotation.
D) varies both daily and seasonally.

Question 8

What happened to the first major atmosphere to develop on the early Earth, which consisted of hydrogen and helium?

A) The molecules reacted chemically with Earth's hot surface and were absorbed into the newly formed rocks.
B) The molecules were quickly absorbed into the ocean since they have high solubility in water.
C) The molecules combined chemically with one another to become molecules that were heavy enough for Earth's gravity to pull into the surface rocks, where they are now found.
D) The atmosphere drifted off into space as Earth's gravity was too weak to hold the light molecules of hydrogen and helium.

Question 9

If Earth is known to have an average albedo of 0.31, what percentage of the sunlight hitting Earth is absorbed by it?

A) 100% - 0.31% = 99.69%-that is, most of it
B) 31%
C) 0.31%, or very little-most of it is reflected into space.
D) 69%

Question 10

The atmosphere breathed now is the _____ atmosphere Earth has had.

A) third
B) second
C) seventh
D) first

Question 11

The major constituents of Earth's atmosphere are

A) 95% carbon dioxide and some water vapor.
B) about equal amounts of methane, ammonia, water vapor, and carbon dioxide.
C) about 80% oxygen and 20% nitrogen.
D) about 80% nitrogen and 20% oxygen.

Question 12

Earth's secondary atmosphere was a hundred times as dense as its present atmosphere, yet the temperature was only sufficient to keep liquid water from freezing and not high enough to vaporize liquid water. Why wasn't the temperature higher?

A) Earth formed beyond the snow line and migrated inward, and at this time it was too far from the Sun to be warm enough to vaporize water.
B) The developing Sun was not as hot as it is now.
C) The secondary atmosphere contained very little carbon dioxide, so there was not enough of a greenhouse effect to enhance the temperature.
D) The dense secondary atmosphere enhanced Earth's albedo. With less radiation striking Earth, the temperature did not rise substantially.

Question 13

What is the approximate ratio of nitrogen to oxygen in Earth's atmosphere?

A) 1 part nitrogen to 2 parts oxygen
B) 4 parts nitrogen to 1 part oxygen
C) 1 part nitrogen to 4 parts oxygen
D) equal parts nitrogen and oxygen

Question 14

What is the approximate ratio of the number of oxygen to nitrogen molecules in Earth's lower atmosphere?

A) 1 oxygen molecule to every 4 nitrogen molecules
B) 4 oxygen molecules to every 1 nitrogen molecule
C) equal numbers of oxygen and nitrogen molecules
D) only 1 oxygen molecule to every 100 nitrogen molecules, or about 1%

Question 15

Why did Earth's earliest atmosphere, composed primarily of hydrogen and helium, NOT last long?

A) Hydrogen is highly reactive, and it soon became bound into chemical compounds in Earth's rocks.
B) Hydrogen and helium are light gases, and they soon escaped into space.
C) Biological activity very quickly combined the hydrogen with oxygen to form water.
D) The hydrogen soon became dissolved in Earth's oceans.

Question 16

What happened to Earth's first atmosphere?

A) It remains part of its present atmosphere, although it has been mixed with nitrogen and oxygen.
B) It was blown away by an early flare-up of the evolving Sun.
C) Its molecules were moving too rapidly to be held by Earth's gravitational pull.
D) It dissolved in the oceans as soon as these were formed.

Question 17

What were the dominant gases in Earth's earliest atmosphere after it first formed?

A) methane and ammonia
B) hydrogen and helium
C) nitrogen and oxygen
D) carbon dioxide and nitrogen

Question 18

The terrestrial planet whose atmosphere is composed primarily of nitrogen is

A) Mars.
B) Venus.
C) Jupiter.
D) Earth.

Question 19

What percentage of the sunlight that falls on Earth is absorbed by Earth rather than reflected into space?

A) almost 100%-the energy contributes significantly to the maintenance of the present surface temperature of Earth.
B) 69%
C) 31%
D) almost none-most of the energy is reflected out into space since the albedo of Earth is relatively high.

Question 20

What would be perhaps the most striking feature that a visiting traveler from outer space would notice on approaching Earth, having examined the rest of the solar system?

A) distinctive and impressive mountain ranges
B) large quantity of liquid water on the surface
C) earthquakes occurring on the solid parts of the surface
D) evidence of volcanoes and lava flow

Question 21

What were the dominant gases in Earth's second atmosphere?

A) nitrogen and oxygen
B) carbon dioxide and water vapor
C) methane and ammonia
D) hydrogen and helium

Question 22

An "ozone hole" is

A) a region centered on the equator where ozone levels are always very low because of destruction by direct sunlight.
B) a region of the stratosphere, often 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 by the corrosive ozone encountered in the stratosphere and 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 accounts for the lack of life-forms there.

Question 23

Billions of years ago, Earth's atmosphere was composed primarily of carbon dioxide. What happened to much of this carbon dioxide?

A) still in the atmosphere
B) dissolved into Earth's oceans
C) broken down into carbon and oxygen by solar ultraviolet light
D) lost to space

Question 24

Ozone in the stratosphere performs an important task that protects life on Earth. What is it?

A) Ozone absorbs the solar wind as it streams into Earth, thereby protecting life from dangerous ionizing radiation.
B) Ozone absorbs much of the dangerous solar ultraviolet light.
C) Ozone acts as a disinfectant, killing dangerous viruses and bacteria that drift in all the time from space before they can reach Earth.
D) Ozone absorbs infrared radiation, thereby providing a comfortable atmospheric temperature on the surface of Earth.

Question 25

Which major constituent of the atmospheres of Venus and Mars is present in only very small amounts in Earth's atmosphere?

A) methane, CH₄
B) carbon dioxide, CO₂
C) nitrogen, N₂
D) oxygen, O₂

Question 26

The large amount of free oxygen in Earth's present atmosphere is primarily a result of

A) outgassing by volcanoes and other geological processes.
B) biological processes such as photosynthesis.
C) splitting of carbon dioxide into carbon and oxygen by solar ultraviolet light.
D) carbon dioxide becoming dissolved in the oceans, releasing oxygen.

Question 27

One of the major differences between Earth and its neighboring planets Venus and Mars is the lack of large quantities of carbon dioxide in its atmosphere near the surface of the planet. If all these planets were originally formed with significant quantities of this gas in their atmospheres, where is this carbon dioxide on Earth at the present time?

A) concentrated high in the atmosphere, where it contributes to the greenhouse effect
B) dissociated by solar UV light into carbon and oxygen, which now exist in abundance as separate chemicals
C) locked up in rocks such as limestone, formed by life-forms in the sea and on Earth's surface
D) dissolved in seawater, a situation that cannot arise on Venus or Mars

Question 28

Photosynthesis in plants on Earth maintains a balance between which of the two atmospheric gases?

A) carbon dioxide and water vapor
B) oxygen and water vapor
C) nitrogen and oxygen
D) oxygen and carbon dioxide

Question 29

The molecular oxygen in Earth's present atmosphere was MOST likely produced

A) at the formation of Earth and has always been present.
B) from volcanic eruptions as the primitive Earth cooled down.
C) from volcanoes, by outgassing.
D) by biological activity such as photosynthesis from green plants.

Question 30

Billions of years ago, Earth's atmosphere was composed primarily of carbon dioxide. Where might one go on Earth to find a large fraction of this carbon dioxide today?

A) nowhere-most of the carbon dioxide has escaped into space
B) anywhere-most of the carbon dioxide is still in the atmosphere, but nitrogen and oxygen have since been added to it
C) to extinct volcanoes, which are composed of rock from Earth's interior that absorbed the carbon dioxide earlier in Earth's history
D) to mountain ranges such as the Rocky Mountains of North America, which are composed largely of limestone

Question 31

Photosynthesis is a chemical process that takes place in green plants. What is its effect on Earth's atmosphere?

A) Photosynthesis consumes carbon dioxide from its atmosphere but produces carbon dioxide at the end of the process and thus has little effect on its atmosphere.
B) Photosynthesis consumes carbon dioxide from its atmosphere and produces oxygen.
C) Photosynthesis consumes oxygen from its atmosphere and produces carbon dioxide.
D) Photosynthesis consumes both water vapor and carbon dioxide from its atmosphere and produces nitrogen.

Question 32

Earth's secondary atmosphere contained a great deal of carbon dioxide, but its present atmosphere contains comparatively little. Where did this carbon dioxide go? Which of these statements does NOT explain what happened to a substantial fraction of this carbon dioxide?

A) The carbon dioxide escaped into space.
B) The carbon dioxide dissolved in the oceans.
C) The carbon dioxide became part of carbonate rocks.
D) The carbon dioxide was trapped underground

Question 33

Which of these is true of the oxygen in Earth's atmosphere?

A) Oxygen is the most abundant gas in Earth's atmosphere.
B) Oxygen is very chemically reactive.
C) The oxygen in Earth's atmosphere exists not as pure oxygen but only in chemical combination with hydrogen in water, carbon in carbon dioxide, and nitrogen in nitrogen oxides.
D) Oxygen is the heaviest molecule in Earth's atmosphere.

Question 34

Where did the majority of the large amount of carbon dioxide (CO₂) from the second major atmosphere to form on the early Earth end up?

A) as nitrogen oxides and carbon, after chemical reactions with the majority component of the atmosphere, the nitrogen molecules
B) absorbed by plant life and transformed into solid carbon and gaseous oxygen
C) dissolved in the oceans and, via the shells of living creatures, in the limestone of many mountain ranges
D) still in the atmosphere, but the quantity of nitrogen and oxygen has since risen to make these constituents the most abundant and relegate carbon dioxide to a minor constituent

Question 35

The presence of oxygen in Earth's atmosphere is thought to result directly from what type of process?

A) volcanic eruptions
B) outgassing of the oceans
C) original condensation of interplanetary gas clouds
D) biological activity of plants and animals

Question 36

Roughly how much more massive was Earth's second atmosphere compared with today's atmosphere?

A) same mass as the present atmosphere
B) 1/10 as massive
C) twice as massive
D) 100 times as massive

Question 37

Which of these processes was NOT important in helping to remove carbon dioxide from Earth's early atmosphere?

A) biological activity
B) dissolving of carbon dioxide into the oceans
C) sedimentation of carbon compounds on the ocean floors
D) escape of carbon dioxide into space

Question 38

Which of these statements about Earth is true?

A) The oxygen in Earth's atmosphere was created by the evaporation of seawater and its dissociation into hydrogen and oxygen by solar UV light.
B) Earth has always had an oxygen-rich atmosphere, which was one reason that life could develop on Earth.
C) Outgassing by volcanic eruptions converted the carbon dioxide-rich atmosphere into an oxygen-rich atmosphere, thus creating conditions in which life could develop.
D) Life developed in a carbon dioxide-rich atmosphere and then converted it into an oxygen-rich atmosphere.

Question 39

Which one of these statements about ozone is NOT correct?

A) It is triple oxygen, O₃.
B) It comprises most of Earth's stratosphere.
C) It absorbs intermediate wavelength ultraviolet radiation from the Sun.
D) It causes the temperature in the stratosphere to rise with altitude.

Question 40

What are ozone holes?

A) small voids on Earth's ozone layer that occur randomly over the entire planet
B) regions of larger-than-normal ozone concentration that appear near the poles
C) regions of smaller-than-normal ozone concentration that appear near the poles
D) seasonal drops in ozone density scattered around the equator

Question 41

The gas temperature in the stratosphere of Earth's atmosphere reaches a maximum at about 50 km. The cause is

A) the absorption of solar ultraviolet radiation by ozone (O₃)_.
B) heating by auroral activity higher in the atmosphere.
C) the ionization of oxygen and nitrogen by solar ultraviolet radiation.
D) turbulence, caused by wind and weather.

Question 42

How does the temperature of Earth's atmosphere vary with height over the range 0-80 km?

A) The temperature decreases, then increases, then decreases again.
B) The temperature rises steadily until it reaches a high and constant value above 80 km.
C) The temperature increases, then decreases, then increases again.
D) The temperature decreases steadily until it reaches a minimum at 80 km.

Question 43

What is the MOST important reason for Earth's need for the ozone layer?

A) The ozone layer protects Earth from the solar wind.
B) The ozone layer allows long-distance radio communication by reflecting radio waves to Earth's surface.
C) The ozone layer shields Earth from harmful solar ultraviolet radiation.
D) The ozone layer provides a convenient dumping site for chlorofluorocarbon chemicals, which are harmful to life.

Question 44

Which of these terms does NOT label a region of Earth's atmosphere or near-Earth environment?

A) ionosphere
B) troposphere
C) stratosphere
D) chromosphere

Question 45

What is the lowest layer in Earth's atmosphere?

A) thermosphere
B) magnetosphere
C) troposphere
D) stratosphere

Question 46

The lowest temperature in Earth's atmosphere occurs at an altitude of about

A) 80 km.
B) 50 km.
C) 10 km.
D) 0 km (the surface of Earth).

Question 47

What is the current status of Earth's ozone layer?

A) The ozone layer is being irreversibly depleted and will probably disappear entirely within the next 200 years.
B) The ozone layer has been distorted-too thin at the poles and too thick over the equatorial regions.
C) The ozone layer has been somewhat depleted, but if left alone, it could restore itself in a century.
D) The ozone layer has become too thick and is moving downward toward the surface, where its heating qualities contribute to global warming.

Question 48

The lowest temperature in Earth's atmosphere is about

A) 3 K.
B) 20 K.
C) 200 K.
D) 273 K.

Question 49

Ozone is a gas consisting of

A) molecules containing combinations of oxygen and nitrogen atoms and electrons.
B) a mixture of several chlorofluorocarbon gases (CFCs).
C) molecules containing 3 oxygen atoms.
D) ionized oxygen atoms, positively charged.

Question 50

Earth's thermosphere is the

A) outermost atmospheric layer in which ultraviolet light from the Sun ionizes atoms.
B) intermediate atmospheric layer in which ultraviolet light from the Sun is absorbed by ozone (O₃) molecules.
C) region of the magnetosphere in which trapped high-energy charged particles spiral along magnetic field lines.
D) layer of molten iron and nickel below the mantle.

Question 51

The chemical constituent that absorbs UV radiation in the stratosphere of Earth's atmosphere, thereby heating these layers to relatively high temperatures, is

A) N₂, nitrogen.
B) CO_2, carbon dioxide.
C) H₂O, water vapor.
D) O₃, ozone.

Question 52

In which layer of Earth's atmosphere is the ozone layer located?

A) mesosphere
B) stratosphere
C) thermosphere
D) troposphere

Question 53

What are the major layers of Earth's atmosphere in the correct order from the surface upward?

A) stratosphere, mesosphere, thermosphere, troposphere
B) mesosphere, troposphere, thermosphere, stratosphere
C) thermosphere, mesosphere, troposphere, stratosphere
D) troposphere, stratosphere, mesosphere, thermosphere

Question 54

Why does the temperature in the stratosphere increase with increasing altitude?

A) The stratosphere is heated by solar ultraviolet radiation absorbed by the ozone layer.
B) Charged particles from the magnetosphere collide with atoms in the stratosphere, depositing energy.
C) Higher altitudes are closer to the Sun and are therefore heated more by it.
D) The stratosphere is heated by solar infrared radiation absorbed by carbon dioxide and water vapor.

Question 55

The coldest layer of Earth's atmosphere is located between the

A) mesosphere and ionosphere.
B) troposphere and Earth's surface.
C) stratosphere and mesosphere.
D) troposphere and stratosphere.

Question 56

The hottest part of Earth's atmosphere is the

A) lowest layer of the troposphere (near Earth's surface).
B) boundary of the upper troposphere with the stratosphere.
C) upper mesosphere.
D) upper ionosphere.

Question 57

Which of these events would NOT be a consequence of the destruction of the ozone layer on Earth?

A) large-scale (perhaps total) destruction of life on Earth
B) large-scale freezing of the oceans
C) drastic increase in ultraviolet radiation at Earth's surface
D) elimination of the rise in temperature in the stratosphere

Question 58

Earth's stratosphere is warmer than the layers above and below it because

A) the methane released when fossil fuel is burned collects in this layer and absorbs infrared light.
B) warm air heated by contact with the ground rises into the stratosphere and heats it.
C) ozone in the stratosphere absorbs specific wavelengths of ultraviolet radiation from the Sun.
D) carbon dioxide in the stratosphere absorbs infrared light radiated outward by the ground.

Question 59

What is the basic structure of Earth's atmosphere?

A) single layer of smoothly decreasing temperature with increasing altitude
B) four layers of alternating temperature profiles: temperature decreasing, then increasing, then decreasing, then increasing with altitude
C) single layer of smoothly increasing temperature with increasing altitude
D) two layers: temperature decreasing with increasing altitude in the lower layer, then increasing with increasing altitude in the upper layer

Question 60

In which layer of Earth's atmosphere does weather occur?

A) stratosphere
B) mesosphere
C) thermosphere
D) troposphere

Question 61

A person is on a commercial airliner flying across the North Atlantic. They are MOST likely near the top of the

A) troposphere.
B) stratosphere.
C) mesosphere.
D) ionosphere.

Question 62

The Mid-Atlantic Ridge is being produced by

A) the weight of the Atlantic Ocean on the thin seabed.
B) tidal flows of ocean water meeting in the mid-Atlantic.
C) two tectonic plates pushing together, producing upthrust.
D) two tectonic plates moving apart because of volcanic upflow.

Question 63

The troposphere of Earth is the

A) atmospheric layer closest to the ground.
B) atmospheric layer above the mesosphere.
C) uppermost layer of solid rock below the planet's crust.
D) atmospheric layer that contains the highest concentration of ozone.

Question 64

In the modern theory of crustal motion on Earth's surface, the process of seafloor spreading is described as the

A) motion of plates toward mid-oceanic ridges and away from continental boundaries.
B) motion of plates away from mid-oceanic ridges and toward continental boundaries.
C) northward motion of some plates and the southward motion of others, causing earthquakes where they slide past each other.
D) rotation of plates around axes that remain stationary on Earth causing plate-edge collisions.

Question 65

The pressure in the atmosphere of Earth varies with altitude by

A) decreasing smoothly with altitude, dropping by about half for every 5.5 km.
B) increasing over a small altitude range above the surface of Earth (about 1 km) and then decreasing smoothly with increasing altitude.
C) remaining a constant up to the height of the highest mountains, then decreasing rapidly.
D) decreasing and increasing several times with increasing altitude, following the temperature variation.

Question 66

The idea of continental drift, as proposed by Wegener around 1915, had one major flaw, which was

A) the absence of a source for the forces and energy required to move the continents.
B) the lack of any evidence that Africa and the Americas had ever been joined.
C) the recent discovery of seafloor spreading, which contradicted the theory.
D) the measured rate of continental motions, which were far greater than predicted.

Question 67

How has the CO₂ concentration in Earth's atmosphere changed over the past thousand years?

A) There are no means of measuring the CO₂ concentration in Earth's atmosphere for times so far past.
B) The CO₂ concentration has remained absolutely constant.
C) The CO₂ concentration has increased steadily.
D) The CO₂ concentration was relatively constant for about 800 years but has increased significantly since 1800 A.D.

Question 68

The pressure in the atmosphere of Earth (or of any other planet) is related to altitude above the planet's surface in what characteristic way?

A) The pressure remains constant with increasing altitude.
B) The pressure decreases by a fixed fraction of each interval of altitude (down by half every 5.5 km on Earth).
C) The pressure decreases and increases several times with increasing altitude, following the temperature variation.
D) The pressure decreases by a fixed amount per unit altitude interval (20% of surface pressure every 5.5 km on Earth).

Question 69

The Mid-Atlantic Ridge is an example of

A) a transformation-fault boundary.
B) a divergent boundary.
C) a convergent boundary.
D) None of these answers is correct.

Question 70

The Mid-Atlantic Ridge in Earth's crust is a region where

A) two tectonic plates are pushing against one another, forcing the ridge upward.
B) two tectonic plates are slowly spreading apart.
C) one tectonic plate is moving below another in a process known as subduction.
D) a single hot plume is pushing molten magma or lava through a break in the crust.

Question 71

What fraction of the total mass of Earth's atmosphere is contained in the troposphere, the lowest layer of Earth's atmosphere?

A) 50%
B) 25%
C) 10%
D) 75%

Question 72

Air pressure falls by roughly a fraction of one-half its pressure for every 5.5-km increase in altitude. What, then, is the air pressure at the top of the troposphere, 11 km above Earth's surface?

A) 33% of that at Earth's surface
B) zero
C) 50% of that at Earth's surface
D) 25% of that at Earth's surface

Question 73

Which fact first gave Alfred Wegener the idea that continents have drifted and are still drifting over Earth's surface?

A) The ocean floors were much younger than the continents, indicating that they were still being formed.
B) The shapes of the east coasts of North and South America fit nicely against those of the west coasts of Europe and Africa.
C) A system of mountains and faults running up the middle of the Atlantic seafloor showed evidence that the crust was spreading apart there.
D) Volcanoes and earthquakes were localized into a well-defined "ring of fire" around the Pacific Ocean and other areas.

Question 74

What is pressure?

A) force times the area over which the force acts
B) force times the distance over which the force acts
C) same as force but expressed in different units
D) force divided by the area over which the force acts

Question 75

The temperature decreases as one moves upward in the troposphere. This is also true in

A) no other atmospheric layer.
B) the stratosphere.
C) the mesosphere.
D) the ionosphere.

Question 76

What happens to the temperature as one goes upward in Earth's ionosphere?

A) The temperature drops as one gets farther from the warm Earth.
B) The temperature drops because the faster (warmer) molecules escape into space, leaving behind the slower (colder) molecules.
C) The temperature rises because of the absorption of ultraviolet energy by the ozone layer.
D) The temperature rises because of the absorption of ultraviolet energy ionizes molecules.

Question 77

The San Andreas fault in California is an example of

A) two tectonic plates pushing directly against one another.
B) an upthrust due to a hot spot in Earth's mantle.
C) a spreading center, where two tectonic plates are being pushed away from each other.
D) two tectonic plates sliding past each other.

Question 78

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 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.

Question 79

Who first postulated that continents drift around over Earth's surface?

A) Charles Darwin
B) Alfred Wegener
C) J. Tuzo Wilson
D) James Van Allen

Question 80

About how much has Earth's surface temperature increased since 1000 A.D.?

A) It has remained absolutely constant.
B) 5°C
C) 0.6°C
D) 15°C