【正文】 3 Now, you remember from our previous discussion that a et’s nucleus ,its core, is made up of ice and dust, like a frozen snowball． crust [kr?st] n. 地殼；外殼 【頻】7 【例】TPO31 L2 As we’ve discussed, Earth’s crust is made up of large plates that rest on a mantle of molten rock. These plates…uh…now these tectonic plates support the continents and oceans. 【衍】crusty adj. 有殼的；crustal adj. 殼的，地殼的；mantle [39。m230。ntl] n. 地幔；覆蓋物 【頻】7 【例】TPO31 L2 As the ocean floor plate begins to sink down into the mantle, it would drag or pull the entire plate along with it. So more and more of this plate, the ocean floor, would go down under the continent into the mantle. slide [sla?d] vi. 滑動(dòng)；滑落；n. 雪崩【頻】7 【例】TPO7 L3 So ice at the base of the glacier melts. And this results in a thin layer of water between the glacier and the ground. This layer of water reduces friction is... is like a lubricant. And it allows the glacier to slide or slip over the bedrock. 【衍】n. slider 滑動(dòng)器；滑雪者；滾動(dòng)之物canyon [39。k230。nj?n] n. 峽谷 【頻】6 【例】TPO1 L2 Now, we geologists thought we had a pretty good idea of how the Grand canyon in the southwestern United States was formed. We knew that it was formed from sandstone that solidified somewhere between 150 and 300 million years ago. lava [39。lɑv?] n. 火山巖漿；熔巖 【頻】6 【例】TPO24 L4 Now, the lava on Venus is thin. It spreads out easily. So shield volcanoes have very gentle sloping sides. They are called shield volcanoes. hemisphere [39。h?m?sf?r] n. 半球 【頻】5 【例】TPO17 L2 Which makes earth, and in particular, the northern hemisphere, warmer. And why is that important? well, because most of the planet’s glaciers are in the northern hemisphere, and if it gets too warm, then glaciers will stop forming. 【衍】hemispheric adj. 半球的，半球形狀的；mineral [39。m?n?r?l] n. 礦物；無機(jī)物 【頻】5 【例】TPO17 L2 Over millions of years, groundwater left deposits of a mineral called calcite, on the rock within Devil39。s Hole. And by studying these clacite deposits, we can determine the climate conditions, the temperatures over the last half million years. 【衍】mine n. 礦，礦藏；礦山，礦井；mineralogy n. 礦物學(xué)；mine v. 開采，采掘；mineralize v. 使礦物化；precipitation [pr?39。s?p?39。te??n] n. 降水，降雨 【頻】5 【例】TPO9 L2 Second, most of the precipitation in the Arctic is in the form of snow. And the snow, which blankets the ground in the winter, actually has an insulating effect on the soil beneath it. 【衍】precipitate v. 沉淀；猛地落下；冷凝成為雨或雪等；swamp [swɑmp] n. 沼澤；濕地 【頻】5 【例】TPO11 L3 Wetlands are areas of marshy, swampy land, areas where water covers the soil, or is present either at or near the surface of the soil for a large part of the year. 【衍】swampy adj. 沼澤的；濕地的；松軟的eruption [?39。r?p??n] n. 爆發(fā)，噴發(fā) 【頻】3 【例】TPO24 L4 It39。s quite possible that this is due to volcanic eruptions, because volcanic eruptions often emit gases. If that39。s the case, volcanism could very well be the root cause of Venus39。s thick cloud cover. 【衍】adj. eruptive 暴發(fā)的，噴出的；erupt v. 爆發(fā)，噴出；evaporate [?39。v230。p?ret] vi. 蒸發(fā)，揮發(fā) 【頻】3 【例】TPO6 L4 Less vegetation means the soil can’t hold water as well, the soil loses its ability to retain water when it does rain. So then you have less moisture to help clouds form, nothing to evaporate for cloud formation. And then the cycle continues, less rain, drier soil, less vegetation, fewer clouds, less rain etc. etc.. 【衍】evaporable adj. 易蒸發(fā)性的，易揮發(fā)的；evaporation n. 蒸發(fā)，消失；extract [39。?kstr230。kt] vt. 開采,提煉 【頻】3 【例】TPO32 L3 It wasn’t the mining itself that caused such massive destruction. It was what happened after the copper ore was extracted from the mines. 【衍】extractable adj. 可抽出的，可榨出的；extraction n. 提取物；extractor n. 提取器；horizontal [39。h?r?39。zɑntl] adj. 水平的；地平線的；【頻】3 【例】TPO24 L3 Today we take for granted that there horizontal bands of plant munities. In the far north, it is tundra, which gives way to forest as you move southward. And even farther south, grasslands take over. But during the Ice Age, these plant munities actually grew together, mixed with one another. 【衍】horizontally adv. 水平地,地平地；horizon ,范圍latitude [39。l230。t?tud] n. 緯度 【頻】3 【例】TPO14 L3 So the Polynesians could estimate their latitude just by looking straight up, by observing whether a certain zenith star passed directly overhead at night, they’d know if they have reached the same latitude as a particular island they were trying to get to. 【衍】latitudinal adj. 緯度的magma [39。m230。ɡm(xù)?] n. 巖漿 【頻】3 【例】TPO14 L4 Remember, magma is hot molten rock that39。s underground, and it is called lava when it reaches the surface. Uh, so the lava builds up, and hardens, and a volcano forms. quartz [kw?rts] n. 石英 【頻】3 【例】TPO8 L3 Another solution was something called a “reading stone”. Around 1000 . European monks would take a piece of clear rock, often quartz, and place it on top of the reading material. The clear rock magnified the letters, making them appear larger. remnant [39。r?mn?nt] n. 殘余物 【頻】3 【例】TPO30 L3 So it’s possible that if the jarosite on Mars was also formed with the help of microorganisms, we might be able to detect remnants of them in the samples we find. slope [slop] n. 斜坡 【頻】3 【例】TPO11 L2 And look at the slope of the roof, the steep angle helps keep off all that rain and snow that accumulates in the winter. topography [t?39。pɑgr?fi] n. 地形學(xué)，地貌學(xué)，地形 【頻】3 【例】TPO24 C2 I guess what I am really confused about is how the topography of the land, the mountains and valleys and stuff, affects precipitation. 【衍】topographical adj. 地志的,地形學(xué)的topographically adv. 從地形上； topology n. 地志學(xué)；canal [k?39。n230。l] n. 運(yùn)河；水道 【頻】2 【例】TPO11 L3 To do that, you have to drain the water from the land, move the water elsewhere, and divert the water sources such as rivers. Hundreds of miles of drainage canals were built in the wetlands. 【衍】canalization n. 運(yùn)河網(wǎng)，開運(yùn)河；canalize v. 開運(yùn)河；erode [?39。rod] vt. 腐蝕，侵蝕 【頻】2 【例】TPO32 L3 So the rain eroded the soil and swept it into the rivers. This is called silting, when soil particles are washed into the rivers. And the silting continued at an