首页
登录
职称英语
[img]2012q1/ct_etoefm_etoeflistz_0758_20121[/img] [br] What is the discussion ma
[img]2012q1/ct_etoefm_etoeflistz_0758_20121[/img] [br] What is the discussion ma
游客
2024-01-04
43
管理
问题
[br] What is the discussion mainly about?
[Professor (male)] Q6 So today I thought we’d focus our discussion on deserts--different types
of deserts.., how they form...that sort of thing. I suppose we should probably
start by defining deserts. You no doubt already know that deserts are tracts
of land that receive meager amounts of annual rainfall. On average, they’re
places that get less than 250 millimeters of rain a year.That...or they lose more
water than they receive. Some other typical features of deserts include sand
dunes and ergs--sand "seas" full of shifting sand dunes. They also have rocky
plateaus. And mineral deposits that were created by evaporation. A general
term for these is evaporites...minerals that are left behind when surface water
evaporates. Uh, some typical evaporites would be...gypsum, and different salts.
OK. Did you realize that deserts account for about a third of the Earth’s land
surface? Pretty amazing, isn’t it? It makes sense if you think about it, though.
Q11 Look at a map...you’ll see deserts covering huge sections of
Africa and Asia--and then there’s Antarctica...
[Student A (female)] That’s a desert?
[Professor] Well...yes. But I can understand why you might be confused. There’re actually
quite a variety of deserts...not just the sandy ones that you might think of first.
Typically, we classify all these different types of deserts according to how they
form. And this can be the result of their geographical location...meaning the
major features of the surrounding land. Or their dominant weather patterns.
Let’s take that second idea...weather patterns...and I’ll give you an example.
Q7 Trade winds. It’ll be good to start with trade winds, because they’re
actually what’s caused the formation of the world’s best-known desert. Do
you know which one I’m referring to?
[Student B (male)] It’s gotta be the Sahara. I’m pretty sure that’s the largest desert on Earth.
[Professor] You’re right about the Sahara being the desert I’m thinking of, but it’s actually
the world’s second-largest desert...next to Antarctica. Q10(A) The Sahara is a
trade-wind desert that was created by the movement of trade winds across
northern Africa.
[Student B] Urn, could you just quickly explain what you mean by trade winds? I’m familiar
with the term, urn, from other geography classes I’ve taken, but I don’t really
know much about them.
[Professor] surprised Oh. Uh, this isn’t something you’ve studied in detail before? Uh,
OK. Sure. Trade winds are the winds that you find near the equator...blowing
almost constantly through the tropics. From the subtropical regions, actually,
to the tropics. In the northern hemisphere, they blow from the northeast. In the
southern hemisphere, they blow from the southeast.
OK. Back to what I was saying about the Sahara.Trade winds traveling toward
the equator cross the Sahara, picking up every last bit of moisture in the land.
And, since they’re moving toward the equator and warming up, their capacity
for holding water is increasing. Because hot air has the capacity to hold a lot of
water. At the same time, though, these trade winds are very dry. When they pass
over the Sahara, they pick up what little water there is.The result is, the land is
left with almost no water at all. It can’t support plants...it becomes a desert.
[Student A] So you’re saying the Sahara turned into a desert not just because it doesn’t get
much rain, but...um, also because these trade winds blow across it and suck out
the moisture?
[Professor] Absolutely right. See how that works? All right. So trade winds are one of the
causes of deserts. Let’s move on to another weather pattern that causes deserts.
The "rain-shadow effect." Q8(B) The name "rain-shadow" has to do with the
location of these deserts...in the shadow of huge mountain ranges. Uh, here’s
how it works. Moist air currents blowing from the sea sweep across land, until
they run into a mountain range. The shape of the mountains basically forces
the moist air to move upward, where it cools, its moisture condenses, and
rain falls. Q8(D) All of the moisture is released on the ocean-facing side of the
mountain range. And by the time it reaches the opposite side of the range, the
air is almost totally dry--no more rain. Q10(C) In extreme cases, this rain-shadow
causes the opposite side of the mountains to turn into a desert. The Mojave
Desert in the United States is affected by this phenomenon.
Moving on...let’s consider coastal deserts. Like rain-shadow deserts, they’re
influenced by the ocean, though the method is somewhat different. They most
often occur along the western edges of continents, where huge, cold currents
in the ocean run parallel to the coast. Q9 What happens is that cold ocean
currents keep rain clouds from forming. They don’t provide much moisture, and
as a result, the coastal region becomes very dry. Q10(B) A good example of a coastal
desert is the Atacama in Chile, which is actually one of the driest places on Earth.
OK, class. I think we’re about out of time for today, but next time we’ll begin
with polar deserts and discuss Antarctica in greater detail.
选项
A、General features used to define what deserts are.
B、Characteristics shared by all types of deserts.
C、The effects of deserts on the global climate.
D、Different factors that lead to the formation of a desert.
答案
D
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3332739.html
相关试题推荐
[img]2012q1/ct_etoefm_etoefwriteb_1920_20121[/img]IndependentWritingDirection
[img]2012q1/ct_etoefm_etoefspeaka_1282_20121[/img]Listenforaquestionabo
[img]2012q1/ct_etoefm_etoeflistz_0445_20121[/img][br]Accordingtotheprofesso
[img]2012q1/ct_etoefm_etoeflistz_0445_20121[/img][br]Whatreasonisgivenfor
[img]2012q1/ct_etoefm_etoeflistz_0445_20121[/img][br]LiStenagaintopartoft
[img]2012q1/ct_etoefm_etoeflistz_0445_20121[/img][br]Accordingtotheprofesso
[img]2012q1/ct_etoefm_etoeflistz_0438_20121[/img][br]Listenagaintopartoft
[img]2012q1/ct_etoefm_etoeflistz_0438_20121[/img][br]Whydoestheprofessorsa
[img]2012q1/ct_etoefm_etoeflistz_0438_20121[/img][br]Whatisthemainpurpose
[img]2012q1/ct_etoefm_etoeflistz_0432_20121[/img][br]Whydoesthestudenttalk
随机试题
Psycholinguisticsisthenamegiventothestudyofthepsychologicalproce
SouthAfricaSafariTopFiveNationalParksandGameReserves[A]ASouth
下列关于固体火灾场所灭火器的最低配置基准表述错误的是()。A.中危险级单具灭火
行政处罚的适用应遵循的基本原则不包括( )。A.行政处罚应从严进行 B.坚持
男性,48岁,8月来诊,发热两周,伴腹痛、腹泻,稀便5~6次/日,有皮疹,体格检
2013年3月20日,姚某、刘某通过特快专递,要求福建省永泰县国土资源局书面公开
A.VLDL B.HDL C.IDL D.CM E.LDL其含量与动脉粥
老年人较青年人发病率更高的疝是A.脐疝 B.腹股沟直疝 C.腹股沟斜疝 D
男性,60岁,排尿困难3个月,体检发现前列腺变硬,为排除前列腺癌,最有价值的实验
违法行为涉嫌犯罪的,行政机关应当及时将案件移送()。A.上级行政机关 B.公
最新回复
(
0
)