[originaltext]W: Dr. Smith. I need to ask you about something in Chapter 12. We

游客2023-07-21  31

问题  
W: Dr. Smith. I need to ask you about something in Chapter 12. Well, it talks about erosion and the de posit of sediment(solid matter that settles at the bottom of a liquid)on the deep sea floor, but I’m confused. For that to happen, there would have to be some kind of force down there moving the mud or sand or whatever, right? But I thought there weren’t any waves or currents that deep in the ocean.
M: That’s not exactly correct. It’s true that deep down on the ocean floor we won’t have the same kinds of currents we find in shallower parts. But we do find what we call turbidity currents. This wasn’t in the book but the term came up in class. Do you remember what it means?
W: Umh, turbidity currents? Oh, yeah! Isn’t that when sediment like sand or mud gets stirred up and mixes with water. And then this mixture flows through the water around it, right?
M: Good !
W: Uhe, but I thought that only happened in rivers.
M: Well, yes. This does occur in rivers, but we see turbidity currents deep in the ocean as well.
W: But how do they get started there?
M: Earthquakes mostly, when an earthquake occurs under water, it throws up tremendous amounts of mud or sand that becomes suspended in a layer of water near the bottom of the ocean. This layer is so much denser and heavier than other ocean water that if flows right down the slopes of the ocean floor and gains more and more speed as it moves along. Then it’s just like the winds blowing across the desert picking up sand from one place and moving it along and finally dropping it somewhere else.

选项 A、The strength of ocean currents.
B、The movement of sediment deep in the ocean.
C、A new way of measuring the depth of the ocean.
D、The best methods for studying deep ocean processes.

答案 B

解析 主旨题。对话一开始女士向男士咨询Chapter 12中让她不明白的内容:it talks about erosion and the deposit of sediment(solid matter that settles at the bottom of a liquid)on the deep sea floor,but I’m confused.,后面对话中男士都是针对此问题展开回答,可见整个对话讨论的话题是海底沉淀物的处置或者动向。
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