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The motion of ocean water ______ at different depths below the surface.
A．modifies
B．varies
C．alters
D．differs
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更多“The motion of ocean water ______ at different depths below the surface.A．modifiesB．variesC”相关的问题
We know from the author's suggestions that
A．we can bargain about the ocean cruises.
B．people with motion sickness should not travel by ships.
C．passengers might be the cause of Norwalk-like viruses.
D．wash hands is a good habit.
A．The upper mantle of the earth behaves as a dense solid.
B．Movements usually occur along lines.
C．Sinking plates cool the surface of the earth.
D．The rising motion currents keep exact pace with them.
Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
No very satisfactory account of the mechanism that caused the formation of the ocean basins has yet been given. The traditional view supposes that the upper layer of the earth behaves as a liquid when it is subjected to small focus for long periods and that differences in temperature under oceans and continents are sufficient to produce movements in the upper layer of the earth with rising currents under the mid- ocean ridges (山脊) and sinking currents under the continents. Theoretically, these movements would carry the continental plates along as though they were on a conveyor belt and would provide the forces needed to produce the split that occur along the ridge. This view may be correct. It has the advantage that the currents are driven by temperature differences that themselves depend on the position of the continents.
On the other hand, the theory is unconvincing because the movements do not normally occur along lines, and it certainly does not occur along lines broken by frequent changes in direction, as the ridge is. Also, it is difficult to see how the theory applies to the plate between the Mid-Atlantic Ridge and the ridge in the Indian Ocean. This plate is growing on both sides, and since there is no intermediate trench, the two ridges must be moving apart. An alternative theory is that the sinking part of the plate, which is denser than the hotter surroundings, pulls the rest of plate after it. Again it is difficult to see how this applies to the ridge in the South Atlantic, where neither the African nor the American plate has a sinking part.
Another possibility is that the sinking plate cools the neighboring mantle (地幔) and produces motion currents that move the plates. This last theory is attractive because it gives some hope of explaining the neighboring mantle and produces motion currents that move the plates. This last theory is attractive because it gives some hope of explaining the enclosed seas. These seas have a typical oceanic floor, except that the floor is overlaid by several kilometers of sediment (沉积物). Their floors have probably been sinking for long periods. It seems possible that a sinking current of cooled material on the upper side of the might be the cause of such deep basins. The enclosed seas are an important feature of the earth's surface and seriously require explanation.
Which of the following titles would best describe the content of the text？
A．Several Theories of Ocean Basin Formation.
B．The Traditional View of the Oceans.
C．Temperature Differences Among the Oceans.
D．Motions and Ocean Currents.
The basic source of most water vapor is the ocean, evaporation, vapor transport, and precipitation (陈雨) make up the continuous movement of water from ocean to atmosphere to land and back to the sea. Rivers return water the sea. In an underground arc (弧) of the cycle, flowing bodies of water discharge some water directly into rivers and some directly to the sea.
What might have been discussed before this passage？
A．The ocean.
B．The earth.
C．The rainfall.
D．The atmosphere.
That the plates are moving is now beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth's interior. It is not possible to determine whether both continents are moving in opposite directions or whether one continent is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layers of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot spot population it appears that the African plate is stationary and that it has not moved during the past 30 mil lion years.
The significance of hot spots is not confined to their role as a frame. of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate comes to rest over a hot spot, the material rising from deeper layer creates a broad dome. As the dome grows, it develops deed fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain their mutability (inconstancy).
The author believes that ______.
A．the motion of the plates corresponds to that of the earth's interior
B．the geological theory about drifting plates has been proved to be truse
C．the hot spots and the plates move slowly in opposite directions
D．the movement of hot spots proves the continents are moving apart
Tsunami
Up until December of 2004, the phenomena of tsunami was not on the minds of most of the world's population. That changed on the morning of December 24, 2004 when an earthquake of moment magnitude 9.1 occurred along the oceanic trench off the coast of Sumatra in Indonesia. This large earthquake resulted in vertical displacement of the sea floor and generated a tsunami that eventually killed 280,000 people and affected the lives of several million people. Although people living on the coastline near the epicenter of the earthquake had little time or warning of the approaching tsunami, those living farther away along the coasts of Thailand, Sri Lanka, India, and East Africa had plenty of time to move to higher ground to escape. But, there was no tsunami warning system in place in the Indian Ocean, and although other tsunami warning centers attempted to provide a warning, there was no effective communication system in place. Unfortunately, it has taken a disaster of great magnitude to point out the failings of the world's scientific community and to educate almost every person on the planet about tsunami.
How Tsunamis Are Generated
There is an average of two destructive tsunamis per year in the Pacific basin. Pacific wide tsunamis are a rare phenomenon, occurring every 10-12 years on the average. Most of these tsunamis are generated by earthquakes that cause displacement of the seafloor.
Earthquakes cause tsunami by causing a disturbance of the seafloor. Thus, earthquakes that occur along coastlines or anywhere beneath the oceans can generate tsunami. The size of the tsunami is usually related to the size of the earthquake, with larger tsunami generated by larger earthquakes. But the sense of displacement is also important. Tsunamis are generally only formed when an earthquake causes vertical displacement of the seafloor. The 1906 earthquake near San Francisco California had a Richter Magnitude of about 7.1, yet no tsunami was generated because the motion on the fault (断层) was strike-slip motion with no vertical displacement. Thus, tsunami only occur if the fault generating the earthquake has normal or reverse displacement. Because of this, most tsunamis are generated by earthquakes that occur along the subduction boundaries of plates, along the oceanic trenches. Since the Pacific Ocean is surrounded by plate boundaries of this type, tsunamis are frequently generated by earthquakes around the margins of the Pacific Ocean.
Examples of Tsunami Generated by Earthquakes
May 22, 1960-A moment magnitude 9.5 earthquake occurred along the subduction zone off South America. Because the population of Chile is familiar with earthquakes and potential tsunami, most people along the coast moved to higher ground. 15 minutes after the earthquake, a tsunami with a run-up of 4.5 m hit the coast. The first wave then retreated, dragging broken houses and boats back into the ocean. Many people saw this smooth retreat of the sea as a sign they could ride their boats out to sea and recover some of the property swept away, by the first wave. But, about 1 hour later, the second wave traveling at a velocity of 166 km/hr crashed in with a run-up of 8 m. This wave crushed boats along the coast and destroyed coastal buildings. This was followed by a third wave traveling at only 83 km/hr that crashed in later with a run-up of 11 m, destroying all that was left of coastal villages. The resulting causalities listed 909 dead with 834 missing. In Hawaii, a tsunami warning system was in place and the tsunami was expected to arrive at 9:57 AM. It hit at 9:58 AM and 61 people died, mostly sightseers that wanted to watch the wave roll in at close range (obviously they were too close). The tsunami continued across the Pacific Ocean, eventually reaching Japan where it killed an additional 185 people.
Prediction and Early Warning
For areas located at
A．Y
B．N
C．NG
Flash forward 34 years, and Norwalk-like viruses (there's a whole family of them) are all over the news as one ocean liner after another limps into port with passengers complaining of nausea and vomiting. The CDC, which gets called in whenever more than 2% of a vessel's passengers come down with the same disease, identified Norwalk as the infectious agent and oversaw thorough ship cleaning—which, to the dismay of the owners of the cruise lines, haven't made the problem go away.
So are we in the middle of an oceangoing epidemic？ Not according to Dave Forney, chief of the CDC's vessel-sanitation program. He sees this kind of thing all the time; a similar outbreak on sever al ships in Alaska last year got almost no press. In fact, he says, as far as gastrointestinal illness goes, fewer people may be getting sick this year than last.
Norwalk-like viruses, it turns out, are extremely common—perhaps second only to cold viruses-and they tend to break out whenever people congregate in close quarters for more than two or three days. Oceangoing pleasure ships provide excellent breeding grounds, but so do schools, hotels, camps, nursing homes and hospitals. "Whenever we look for this virus," says Dr. Marc Widdowson, a CDC epidemiologist, "we find it." Just last week 100 students (of 500) at the Varsity Acres Elementary School in Calgary, Canada, stayed home sick. School trick？ Hardly. The Norwalk virus had struck again.
If ocean cruises are your idea of fun, don't despair. This might even be a great time to go shipping for a bargain. The ships have been cleaned. The food and water have been examined and found virus free. According to the CDC, it was probably the passengers who brought the virus aboard.
Of course, if you are ill or recovering from a stomach bug, you might do everybody a favor and put off your travel until the infectious period has passed (it can take a couple of weeks). To reduce your chances of getting sick, the best thing to do is wash your hands—frequently and thoroughly—and keep them out of' your mouth.
One more thing: if, like me, you are prone to motion sickness, don't forget to pack your Drama mine.
According to the passage, CDC is an organization that
A．works against the Norwalk-like viruses.
B．helps to control diseases.
C．specialized in treat virus in ocean liners.
D．works for the benefits of cruise owners.
Passage Two After years’ of being hung up because of the spendings far outweighing profits, deep sea mining is now emerging as a serious threat to the stability of ocean systems and processes that have yet to be understood well enough to punish in good conscience their large-scale destruction. Key to assessing what is at risk are technologies needed to access the deep sea. The mining company, Nautilus Minerals, has invested heavily in mining machinery. However, resources needed for independent scientific evaluation at those depths are essentially non-existent. The role of life in the deep sea relating to the carbon cycle is vaguely understood, and the influence of the microbial (微生物的) systems (only recently discovered) and the diverse ecosystems in the water column and sea bed have yet to be thoughtfully analyzed. The principle of exploiting minerals in the deep sea is based on their perceived current monetary value. The living systems that will be destroyed are perceived to have no monetary value. Will decisions about use of the natural world continue to be based on the financial advantage for a small number of people despite risks to systems that maintain planetary stability — systems that support human survival？ The IUCN (International Union for Conservation of Nature) World Conservation Congress helps set in motion some significant and very timely actions that could help blunt the sharp edge of enthusiasm for dividing up the deep ocean. Whatever it takes, there must be ways to elevate recognition of the critical importance of intact natural systems. We need technologies to access the deep sea to independently explore and understand the nature of Earth’s largest living system. But most importantly, we need the will to challenge and change the attitudes, traditions and policies about the natural world that have driven us to burn through the assets as if there is no tomorrow. This “as if” can be a reality — or not — depending on what we do now. Or what we fail to do. However, there is undeniably cause for hope: there is still time to choose. 30. What is the author’s attitude toward deep sea mining？
A、Objective.
B、Pessimistic.
C、Suspicious.
D、Indifferent.
In describing the way a seafloor disturbance such as movement along a fault
reshapes the sea surface into a tsunami, modelers assume the sea-surface
displacement is identical to that of the ocean bottom, but direct measurements
Line of seafloor motion have never been available. Researchers presently use an
(5) idealized model of the quake: they assume that the crustal plates slip past one
another along a simple, rectangular plane. As modelers scramble to guide
tsunami survey teams immediately after an earthquake, only the orientation of
the assumed fault plane and the quake's location, magnitude and depth can be
interpreted from the seismic data alone.
(10) As all other parameters must be estimated, this first simulation frequently
underestimates inundation, which can signify that the initial tsunami height was
also understated when the single-plane fault model distributes seismic energy
over too large an area. Analyses of seismic data cannot resolve energy
distribution patterns any shorter than the seismic waves themselves, which
(15) extend for several hundred kilometers, but long after the tsunami strikes land,
modelers can work backward from records of run-up and additional earthquake
data to refine the tsunami's initial height. For example, months of aftershocks
eventually reveal patterns of seismic energy that are concentrated in regions
much smaller than the original, single-plane fault model assumed. When seismic
(20) energy is focused in a smaller area, the vertical motion of the seafloor-and
therefore the initial tsunami height-is greater. Satisfactory simulations are
difficult, but improve immeasurably scientists' ability to make better
predictions.
Propagation of the tsunami transports seismic energy away from the
(25) earthquake site through undulations of the water, just as shaking moves the
energy through the earth. At this point, the wave height is so small compared
with both the wavelength and the water depth that researchers can apply linear
wave theory, which predicts that the velocity of tsunami increases with the
depth of the water and the length of the wave. This dependence of wave speed
(30) on water depth means that refraction by bumps and grooves on the seafloor can
shift the wave's direction, especially as it travels into shallow water. In
particular, wave fronts tend to align parallel to the shoreline so that they wrap
around a protruding headland before smashing into it with greatly focused
incident energy. At the same time, each individual wave must also slow down
(35) because of the decreasing water depth, so they begin to overtake one another,
decreasing the distance between them in a process called shoaling. Refraction
and shoaling squeeze the same amount of energy into a smaller volume of water,
creating higher waves and faster currents. In the last stage of evolution,
inundation and run-up, in which a tsunami may run ashore as a breaking wave or
(40) a wall of water or a tide-like flood, the wave height is now so large that it is
difficult to assess the complicated interaction between the water and the shoreline.
The primary function of the
A．introduce a new explanation of a physical phenomenon
B．explain how a physical phenomenon is measured and described
C．illustrate the limitations of applying mathematics to complicated physical phenomena
D．indicate the direction that research into a particular physical phenomenon should take
E．clarify the differences between an old explanation of a physical phenomenon and a new model of it
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