冰河世纪 在地质历史上曾经出现过气候寒冷的大规模冰川活动的时期,称为冰期这种冰期曾经有过三次,即前寒武晚期、石炭-二叠纪和第四纪。第四纪冰期来临的时候,地球的年平均气温曾经比现在低10℃~15℃,全球有1/3以上的大陆为冰雪覆盖,冰川面积达5200万平方千米,冰厚有1000米左右,海平面下降130米。第四纪冰期又分4个冰期和3个间冰期。间冰期时,气候转暖,海平面上升,大地又恢复了生机。第四纪冰期的遗迹最多,如斯堪的纳维亚半岛的峡湾,北欧、中欧、北美众多的冰碛残丘,阿尔卑斯山的U型谷和陡峭的山峰,法国和瑞士交界处侏罗山巨大的冰漂砾等,都是第四纪冰川作用留下的产物。 冰期有广义和狭义之分,广义的冰期又称大冰期,狭义的冰期是指比大冰期低一层次的冰期。大冰期是指地球上气候寒冷,极地冰盖增厚、广布,中、低纬度地区有时也有强烈冰川作用的地质时期。大冰期中气候较寒冷的时期称冰期,较温暖的时期称间冰期。大冰期、冰期和间冰期都是依据气候划分的地质时间单位。大冰期的持续时间相当地质年代单位的世或大于世,两个大冰期之间的时间间隔可以是几个纪,有人根据统计资料认为,大冰期的出现有1.5亿年的周期。冰期、间冰期的持续时间相当于地质年代单位的期。 在地质史的几十亿年中,全球至少出现过3次大冰期,公认的有前寒武纪晚期大冰期、石炭纪-二叠纪大冰期和第四纪大冰期。冰川活动过的地区,所遗留下来的冰碛物是冰川研究的主要对象。第四纪冰期冰碛层保存最完整,分布最广,研究也最详尽。在第四纪内,依冰川覆盖面积的变化,可划分为几个冰期和间冰期,冰盖地区约分别占陆地表面积的30%和10%。但各大陆冰期的冰川发育程度有很大差别,如欧洲大陆冰盖曾达北纬48°,而亚洲只达到北纬60°。由于气候变化随地区的差异和研究方法的不同,各地冰期的划分有所不同。1909年,德国的A.彭克和E.布吕克纳研究阿尔卑斯山区第四纪冰川沉积,划分和命名了4个冰期和3个间冰期。随后,世界各地也都划分出相应的冰期和间冰期。 大冰期的成因,有各种不同说法,但许多研究者认为可能与太阳系在银河系的运行周期有关。有的认为太阳运行到近银心点区段时的光度最小,使行星变冷而形成地球上的大冰期;有的认为银河系中物质分布不均,太阳通过星际物质密度较大的地段时,降低了太阳的辐射能量而形成地球上的大冰期。 第四纪是地球历史的最新阶段,始于距今175万年。第四纪包括更新世和全新世两个阶段,二者的分界以地球上最近一次冰期结束、气候转暖为标志,大约在距今1万年前后。 在近一百万年的第四纪中,有过几次冰川期,在冰期之间又有过气候较暖的间冰期。冰期和间冰期的交替造成了地球上冰川的扩展和退缩,并对整个地理环境特别是生物界有极大的影响。 一般所说的冰河时代,主要是指第四纪的大冰川的时代。因为它离我们最近,在地貌及沉积物等方面遗留下许多痕迹,使我们对它了解的比较详细。实际上在整个地球发展史中发生过好几次这样的大冰期,有时冰川的范围扩大到目前在赤道附近的南非、印度和澳洲。根据发展的观点来看,地球上今后还有可能发生大冰川的降临。 第四纪生物界的面貌已很接近于现代。哺乳动物的进化在此阶段最为明显,而人类的出现与进化则更是第四纪最重要的事件之一。Ice ageIn the geological history ever seen massive ice cold periods of activity, called the glacial ice had three times before, namely cambrian-ordovician late Permian strata, and quaternary. The quaternary glacial comes, the earth's average temperature, lower than ever now 10 degrees ~ 15 ° c, has more than 1/3 of the continental glacial ice, for the area of 52 million square kilometers, ice thickness is 1,000 meters, sea-level drop 130 meters. The quaternary glacial and four glacial and interglacial stage 3. Climate warmer interglaciations, rising sea levels, the earth and restore the vitality. Most of the quaternary glacial period, such as the remains of Scandinavia, northern, central and fjords in North America many moraines, residual u-shaped valley in the Alps and steep peaks, France and Switzerland junction of great drift ice roshan Jurassic debris, is leaving the quaternary glaciers function of the product.Ice is broad and narrow, generalized glacial ice and respond, narrow glacial ice refers to a lower level than the ice. Large ice cold climate refers to earth, the polar ice caps, thickening, and sometimes also have strong low-latitude region of the role of geological period glacier. The weather was cold in large glacial periods of ice, says the warm interglacial period said. Big glacial and interglacial stage, is all according to the division of geological time climate. The duration of large ice in the world geological unit is greater than the two big, or the time interval between the ice age, someone may be several according to statistics, there is another big 1.5 million cycles. The duration of ice, interglacial period of the equivalent of geological units.Billions of years in the geologic history, global at least three major glaciations occurred, acknowledged Precambrian late carboniferous and Permian big glacial ice and quaternary glaciations big big. The glacier activities, from moraines is the main research object of glacier. The quaternary glacial moraines layer of the most intact, the most popular, the most detailed study. In the quaternary glacial area, according to the change, can be divided into several and interglacial stage, the ice area approximately 30% of the land surface respectively, and 10%. But the development degree of mainland glacial ice, such as Europe, there was a big difference between mainland of 48 ° latitude ice once, while Asian only achieve latitude 60 °. Due to climate change, and the difference of the district with the different research methods, the ice into different. In 1909, A German PengKe and e. BuLvKeNa research into sedimentary, quaternary glaciers Alps and the four glacial and interglacial stage 3. Then, all over the world are divided into the corresponding and interglacial stage.The ice formation, great variety, but many researchers think in the Milky Way and solar cycle. Some think the sun to close at heart point section of silver, make the planet spectrophotometry and cold on the earth; the glacial Some think in the galaxy, the physical distribution inequality through interstellar density large area, reduce the sun's radiation energy and formation of ice on the earth.Is the history of the earth's latest quaternary started dating 175 million stage. The quaternary includes two stages of succession and holocene, both on the boundary expansion ends on earth, climate warmer, about 1 million years ago.In nearly 100 years in the quaternary, have several times during the ice ages, between ice and had a warmer climate interglacial periods. And interglacial stage of the earth caused by the expansion and shrinking glaciers, and the geographical environment has great influence (especially.The general says the last ice age and mainly refers to the era of quaternary glaciers. Because it is nearer to us, in the aspects of landform and sediment left many traces, that we know about it in detail. In the whole earth history in actually occurred several big glacial ice, sometimes the expanded to present at the equator in South Africa, India and Australia. According to the development viewpoint, the earth may also occur in large glaciers.The image of the quaternary dynamic-earth very close to the modern. In mammals