Early in its history, Earth was molten and had neither atmosphere nor oceans. However, as the gradually cooling surface began to solidify into rock, intense heat trapped below Earth’s outer crust had to get out somehow. The result was surely volcanoes, geysers, earthquakes, and a variety of other geological events that literally blew off steam and pent-up heat through cracks in the surface. “Outgassing” of this sort happens even today: though at only a few locations on Earth and rather infrequently at that.But several billion years ago, this type of geological activity was surely more widespread and frequent. Scrutiny of modern volcanoes shows that lots of steamy water vapor, carbon dioxide, and nitrogen would have then undoubtedly emerged, along with vast quantities of ash and dust. Smaller amounts of hydrogen, oxygen, and other gases doubtless accompanied these early planetary eruptions. Calculations imply that over the course of Earth’s history enough gas was exhaled through fissures from Earth’s interior to create much of our current atmosphere. The rest presumably came from comets and meteorites that could have scattered large quantities of matter on young Earth. Even today, some 40 thousand tons of extraterrestrial matter falls to Earth each year almost all of it burning in the air or splashing in the ocean.
The origin of our present atmosphere is therefore a combination of terrestrial outgassing and interplanetary assault (further changed by later biological events). In truth, Earth’s atmosphere is perhaps still adjusting, as present-day volcanoes occasionally sputter gas and heat amid incoming debris arriving from space. Todays atmosphere was not, however, derived directly from a mixture of interstellar gases The composition of Earth’s atmosphere thus differs considerably from the average cosmic abundance of the elements.
Since the atmosphere and oceans of planet Earth are so closely linked, they almost certainly originated, at least partly, from the same sources—our planet’s interior and materials from space As regards the ocean, geologists argue that as the surface cooled sufficiently, the first store of liquid water pooled as water vapor condensed After all, steam is the main component of volcanically vented matter, and the hydrated rocks (mostly silicates: with water trapped inside) that today make up Earth’s mantle (the layer immediately below the crust) store several times more water than in all the seas combined. But outgassing from within may not be the whole story since our planet’s water has chemical subtleties implying that some of it may have come from beyond.
Debate swirls among geologists concerning the rate and timing of ocean formation. We are unsure whether Earth’s mantle outgassed the global seas all at once early in our planet’s history— known among geologists as the “big burp” theory. Or perhaps the seas took some time to form; having secreted from Earth’s interior in a series of volcanic events that occurred more gradually. Researchers argue that some of the waters of Earth have resulted from a rain of water-rich comets and meteorites that collided with our planet in great numbers during its first billion years A minority of researchers go so far as to argue that all of Earth’s water originated in this way, but this extreme view does not fit with the fact that the makeup of water on Earth does not match that trapped in interplanetary bodies. Three comets that recently bypassed Earth—Halley’s in 1986, Hyakutake in 1996, and Hale-Bopp in 1997—all emitted radiation that revealed a higher concentration of water with heavy hydrogen atoms than is found in Earth’s oceans.
Most likely—as with many other aspects of the cosmic evolutionary story that are neither black nor white, neither solely this nor clearly that—Earth’s large bodies of seawater emerged from both within and without, and then, as the rate of outgassing and bombardment declined, a global recycling system began to operate. Water locked in rocks was expelled back into the ocean whenever the rocks were heated, such as those near volcanoes. To be sure: most of today’s seawater is thought to have been recycled many times, perhaps as frequently as every ten million years. Recently, water has been directly observed emanating from certain underwater vents Whether this is “juvenile” water still originating directly from Earth’s mantle and incrementally adding to the world’s supply or merely existing seawater cycling through the vents is not yet known.
题目：
1
Early in its history, Earth was molten and had neither atmosphere nor oceans. However, as the gradually cooling surface began to solidify into rock, intense heat trapped below Earth’s outer crust had to get out somehow. The result was surely volcanoes, geysers, earthquakes, and a variety of other geological events that literally blew off steam and pent-up heat through cracks in the surface. “Outgassing” of this sort happens even today: though at only a few locations on Earth and rather infrequently at that.But several billion years ago, this type of geological activity was surely more widespread and frequent. Scrutiny of modern volcanoes shows that lots of steamy water vapor, carbon dioxide, and nitrogen would have then undoubtedly emerged, along with vast quantities of ash and dust. Smaller amounts of hydrogen, oxygen, and other gases doubtless accompanied these early planetary eruptions. Calculations imply that over the course of Earth’s history enough gas was exhaled through fissures from Earth’s interior to create much of our current atmosphere. The rest presumably came from comets and meteorites that could have scattered large quantities of matter on young Earth. Even today, some 40 thousand tons of extraterrestrial matter falls to Earth each year almost all of it burning in the air or splashing in the ocean.
The word “Scrutiny” in the passage is closest in meaning to
Abasic knowledge
Bfrequent comparison
Cpowerful eruption
Dclose observation
2
Early in its history, Earth was molten and had neither atmosphere nor oceans. However, as the gradually cooling surface began to solidify into rock, intense heat trapped below Earth’s outer crust had to get out somehow. The result was surely volcanoes, geysers, earthquakes, and a variety of other geological events that literally blew off steam and pent-up heat through cracks in the surface. “Outgassing” of this sort happens even today: though at only a few locations on Earth and rather infrequently at that.But several billion years ago, this type of geological activity was surely more widespread and frequent. Scrutiny of modern volcanoes shows that lots of steamy water vapor, carbon dioxide, and nitrogen would have then undoubtedly emerged, along with vast quantities of ash and dust. Smaller amounts of hydrogen, oxygen, and other gases doubtless accompanied these early planetary eruptions. Calculations imply that over the course of Earth’s history enough gas was exhaled through fissures from Earth’s interior to create much of our current atmosphere. The rest presumably came from comets and meteorites that could have scattered large quantities of matter on young Earth. Even today, some 40 thousand tons of extraterrestrial matter falls to Earth each year almost all of it burning in the air or splashing in the ocean.
The word “undoubtedly” in the passage is closest in meaning to
Acertainly
Bslowly
Cforcefully
Dpredictably
3
Early in its history, Earth was molten and had neither atmosphere nor oceans. However, as the gradually cooling surface began to solidify into rock, intense heat trapped below Earth’s outer crust had to get out somehow. The result was surely volcanoes, geysers, earthquakes, and a variety of other geological events that literally blew off steam and pent-up heat through cracks in the surface. “Outgassing” of this sort happens even today: though at only a few locations on Earth and rather infrequently at that.But several billion years ago, this type of geological activity was surely more widespread and frequent. Scrutiny of modern volcanoes shows that lots of steamy water vapor, carbon dioxide, and nitrogen would have then undoubtedly emerged, along with vast quantities of ash and dust. Smaller amounts of hydrogen, oxygen, and other gases doubtless accompanied these early planetary eruptions. Calculations imply that over the course of Earth’s history enough gas was exhaled through fissures from Earth’s interior to create much of our current atmosphere. The rest presumably came from comets and meteorites that could have scattered large quantities of matter on young Earth. Even today, some 40 thousand tons of extraterrestrial matter falls to Earth each year almost all of it burning in the air or splashing in the ocean.
According to paragraph 1, all of the following are true of out gassing EXCEPT:
AIt involves volcanoes, geysers, earthquakes, and other geological activities.
BToday it can take place at any location on Earth’s surface.
CThe gases that emerged as a result of it billions of years ago included some hydrogen and oxygen.
DIt occurred more frequently in the past than it does today
4
Early in its history, Earth was molten and had neither atmosphere nor oceans. However, as the gradually cooling surface began to solidify into rock, intense heat trapped below Earth’s outer crust had to get out somehow. The result was surely volcanoes, geysers, earthquakes, and a variety of other geological events that literally blew off steam and pent-up heat through cracks in the surface. “Outgassing” of this sort happens even today: though at only a few locations on Earth and rather infrequently at that.But several billion years ago, this type of geological activity was surely more widespread and frequent. Scrutiny of modern volcanoes shows that lots of steamy water vapor, carbon dioxide, and nitrogen would have then undoubtedly emerged, along with vast quantities of ash and dust. Smaller amounts of hydrogen, oxygen, and other gases doubtless accompanied these early planetary eruptions. Calculations imply that over the course of Earth’s history enough gas was exhaled through fissures from Earth’s interior to create much of our current atmosphere. The rest presumably came from comets and meteorites that could have scattered large quantities of matter on young Earth. Even today, some 40 thousand tons of extraterrestrial matter falls to Earth each year almost all of it burning in the air or splashing in the ocean.
According to paragraph 1, which of the following is true of comets and meteorites?
ADuring the planet’s early history: they deposited about 40 thousand tons of material each year.
BThey are probably responsible for beginning many of the outgassing events in Earth’s early history.
CMost of the gases they brought to Earth burned off long ago.
DThey probably made a significant contribution to the formation of Earth’s atmosphere.
5
Since the atmosphere and oceans of planet Earth are so closely linked, they almost certainly originated, at least partly, from the same sources—our planet’s interior and materials from space As regards the ocean, geologists argue that as the surface cooled sufficiently, the first store of liquid water pooled as water vapor condensed After all, steam is the main component of volcanically vented matter, and the hydrated rocks (mostly silicates: with water trapped inside) that today make up Earth’s mantle (the layer immediately below the crust) store several times more water than in all the seas combined. But outgassing from within may not be the whole story since our planet’s water has chemical subtleties implying that some of it may have come from beyond.
According to paragraph 3, how do geologists think Earth’s oceans initially formed?
AHydrated rocks released a portion of their water to the surface of Earth.
BMaterials from space formed pools of water on Earth’s surface.
CSteam in the atmosphere condensed and pooled once the planet cooled enough.
DVolcanoes created areas on Earth’s surface where water could pool.
6
Since the atmosphere and oceans of planet Earth are so closely linked, they almost certainly originated, at least partly, from the same sources—our planet’s interior and materials from space As regards the ocean, geologists argue that as the surface cooled sufficiently, the first store of liquid water pooled as water vapor condensed After all, steam is the main component of volcanically vented matter, and the hydrated rocks (mostly silicates: with water trapped inside) that today make up Earth’s mantle (the layer immediately below the crust) store several times more water than in all the seas combined. But outgassing from within may not be the whole story since our planet’s water has chemical subtleties implying that some of it may have come from beyond.
Which of the following can be inferred from paragraph 3 about the water trapped within Earths’mantle?
AIt differs chemically in some respects from the water in Earth’s oceans.
BIt is a relatively small amount compared to the amount of water on Earth’s surface.
CIt is released into the oceans at a higher rate than into the atmosphere.
DIts release by volcanoes cannot explain the volume of water found in the oceans
7
Debate swirls among geologists concerning the rate and timing of ocean formation. We are unsure whether Earth’s mantle outgassed the global seas all at once early in our planet’s history— known among geologists as the “big burp” theory. Or perhaps the seas took some time to form; having secreted from Earth’s interior in a series of volcanic events that occurred more gradually. Researchers argue that some of the waters of Earth have resulted from a rain of water-rich comets and meteorites that collided with our planet in great numbers during its first billion years A minority of researchers go so far as to argue that all of Earth’s water originated in this way, but this extreme view does not fit with the fact that the makeup of water on Earth does not match that trapped in interplanetary bodies. Three comets that recently bypassed Earth—Halley’s in 1986, Hyakutake in 1996, and Hale-Bopp in 1997—all emitted radiation that revealed a higher concentration of water with heavy hydrogen atoms than is found in Earth’s oceans.
Why does the author make the statement “Three comets that recently bypassed Earth—Halley’s in 1986, Hyakutake in 1996, and Hale-Bopp in 1997—all emitted radiation that revealed a higher concentration of water with heavy hydrogen atoms than is found in Earth’s oceans” ?
ATo provide evidence against the claim that all of Earth’s water might have come from comets and meteorites
BTo demonstrate that the chemical makeup of interplanetary bodies has changed significantly since Earth’s early history
CTo argue that the heavy-water content of Earth’s oceans is likely to increase as more comets and meteors hit the planet
DTo support the claim that the water on comets has a unique chemical makeup not found elsewhere in the solar system
8
Most likely—as with many other aspects of the cosmic evolutionary story that are neither black nor white, neither solely this nor clearly that—Earth’s large bodies of seawater emerged from both within and without, and then, as the rate of outgassing and bombardment declined, a global recycling system began to operate. Water locked in rocks was expelled back into the ocean whenever the rocks were heated, such as those near volcanoes. To be sure: most of today’s seawater is thought to have been recycled many times, perhaps as frequently as every ten million years. Recently, water has been directly observed emanating from certain underwater vents Whether this is “juvenile” water still originating directly from Earth’s mantle and incrementally adding to the world’s supply or merely existing seawater cycling through the vents is not yet known.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
AAlthough the cosmic evolutionary story remains somewhat unclear, it seems likely that Earth’s oceans formed and began to recycle before outgassing and bombardment declined.
BEarth’s oceans probably originated from a combination of outgassing and bombardment, and its waters began recycling when these activities became less frequent.
COnce the rate of outgassing and bombardment declined, it seems likely that a global system of ocean water recycling began.
DThe global system of recycling probably began once Earth’s oceans grew large from water sources within and outside the planet.
