【填空答案】

1. oceanographer: n. ［C］海洋學者，海洋研究者
2. sediment: n. ［C］沉淀物
3. evaporated v.蒸發，消失
4. frozen vt. 結冰
5. continental adj.大陸的
6. glacier: n. ［C］冰河
7. drain: v. 排出，排水
8. pollutant: n. ［C］污染物質

【聽力原文】

One reason oceanographers analyze the sediment on the ocean floor is to see how long-term changes inEarth's temperature have affected the depth of the ocean. By analyzing theremains of sea animals in old layers of ocean sediment, oceanographers can determinethe depth of the ocean in the past. They've analyzed hundreds of such layers,including some from the coldest periods of Earth's history—the ice ages. Whatthey've found is that during the ice ages, the amount of water in the oceansdecreased. Water levels in the ocean dropped by about four hundred feet. Waterfrom the ocean evaporated and became frozen in continental glaciers, so itdidn't drain back into the ocean. When temperatures eventually rose again, theglaciers melted, and the oceans returned to their former depths. Analysis ofsedimentary data indicates that periods of glacial freezing and meltingoccurred in regular cycles of twenty thousand, forty thousand, and one hundredthousand years.
Oceanographers are interested in the history of seawater levels because theyhope to use this historical data in order to predict the possible effect thatglobal warming could have on seawater levels. If industrial pollutants arecapable of heating global temperatures to the point that glaciers begin to melt,it is urgent for us to know precisely how high sea levels will rise as aresult.

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