《新概念4Lesson 30课文.docx》由会员分享，可在线阅读，更多相关《新概念4Lesson 30课文.docx（4页珍藏版）》请在金锄头文库上搜索。
1、Lesson 30Exploring the sea-floor海底勘探Our knowledge of the oceans a hundred years ago was confined to the two-dimensional shape of the sea surface and the hazards of navigation presented by the irregularities in depth of the shallow water close to the land.100年前，我们只知道海洋是二维平面形的，以及靠近陆地浅水区的深浅不一能给航行带来危险。T
2、he open sea was deep and mysterious, and anyone who gave more than a passing thought to the bottom confines of the oceans probably assumed that the sea bed was flat.无边无际的海洋深邃而又神秘，凡是稍稍想过大海海底的人大概都会认为海底是平坦的。Sir James Clark Ross had obtained a sounding of over 2400 fathoms in 1839, but not until 1869, w
3、hen H.M.S. Porcupine was put at the disposal of the Royal Society for several cruises, that a series of deep soundings was obtained in the Atlantic and the first samples were collected by dredging the bottom.1893年，詹姆斯克拉克罗斯爵士曾测得海水深度超过2400英寻；但直到1869年，皇家学会用英国“豪猪”号舰艇进行了几次巡航后，才在大西洋测得一个个海水深度，同时通过挖掘海底，取得了研
4、究海底的首个样品。Shortly after this the famous H.M.S. Challenger expedition established the study of the sea-floor as a subject worthy of the most qualified physicists and geologists.此后不久，英国著名的“挑战者号”舰艇对海底的那次考察，把对海床的研究确立为一个值得一流物理学家和地质学家从事的研究课题。A burst of activity associated with the laying of submarine cable
5、 soon confirmed the Challengers observation that many parts of the ocean were two to three miles deep, and the existence of underwater features of considerable magnitude.铺设海底电缆的热潮很快证实了“挑战者号”的观察结果：海洋中很多地方可深达两三英里，水下差异极大。Today, enough soundings are available to enable a relief map of the Atlantic to be
6、 drawn and we know something of the great variety of the sea beds topography.现在已有足够的水深测量数据来绘制一张大西洋洋底地形图, 而且我们对海底地形的千变万化也有了一定的了解。Since the sea covers the greater part of the earths surface, it is quite reasonable to regard the sea floor as the basic form of the crust of the earth, with superimposed u
7、pon it the continents, together with the islands and other features of the oceans.既然海洋覆盖着地球的大部分的表面，因此完全有理由把海床看作地壳的基本模壳，上面附加着大陆以及岛屿和海洋的其他形态。The continents form rugged tablelands which stand nearly three miles above the floor of the open ocean.大陆是崎岖不平的高低，高出辽阔海洋海底近三英里。From the shore line, out to a dist
8、ance which may be anywhere from a few miles to a few hundred miles, runs the gentle slope of the continental shelf, geologically part of the continents.从海岸线向大海延伸几英里到几百英里的区域是大陆架慢坡，从地质学上来说，它是大陆的一部分。The real dividing line between continents and oceans occurs at the foot of a steeper slope.大陆和海洋的的真正分界线是
9、在陡坡脚下。This continental slope usually starts at a place somewhere near the 100-fathom mark and in the course of a few hundred miles reaches the true ocean floor at 2500-3500 fathoms.大陆架慢坡一般是从差不多100英寻深的地方开始的，一直延伸到几百英里远，深达2500至3500英寻深的地方，那里才是真正的海底。The slope average about 1 in 30, but contains steep, pr
10、obably vertical, cliffs and gentle sediment-covered terraces, and near its lower reaches there is a long tailing-off which is almost certainly the results of material transported out to deep water after being eroded from the continental masses.坡度平均约为30分之1，但其中包括陡峭的乃至垂直的峭壁和沉积物覆盖的缓和阶梯地带，在这个地带的低处是很长的一段尾沙地段，基本上可以断定这个地段是大陆块体上侵蚀下来的物质，被水冲到深水处形成的。
