罗布泊历史环境变化探讨

AN APPROACH TO THE ENVIONMENTAL CHANGES IN LOP-NUR HISTORY

1972年美国地球资源卫星发现“中国西部的大耳朵”罗布泊干涸了,但在地质历史时期罗布泊曾是2×10~4km^2的大湖,在1958年前还曾有2919km^2。历史上罗布泊有过多次丰水和萎缩干涸的历史,但在近万年来它毕竟是塔里木盆地盐分最终的积聚洼地,而不是游移湖,古湖心沉淀的大面积厚岩盐层就是明证(聚集盐50亿t^80亿t)。塔里木河虽多次改道,只是引起入湖口水面形状的变化。罗布泊面积多次萎缩,与历史上农垦事业发展相关,1400年前明显萎缩,为河流自然改道所致,同时引起楼兰古城衰亡。近代罗布泊干涸,是人类影响的结果。从卫星象片分析,古罗布泊有6条明显的萎缩影痕,1921年以后的近代罗布泊有4条萎缩影痕,与以上原因相对应。鉴于目前塔里木盆地干旱气候条件和人类经济发展状况,罗布泊干涸和湖周荒漠化的状况不会改变。

In 1972. It was discovered by earth resources satellite of USA that Lop-Nur. which is known as a big ear shaped of in west China had dried up. Anyhow in the geological peroid. Lop-Nur was a big lake of 2X 10'km2, even before the 1958. It covered an area of 2 919 km2. In or-der to set up the Lop-Nur Nature Reserve. We went to Lop nor area for five times from 1995 to 1997. In the spring of 1996, we reached Loulan Ancient city from the center of Lop-Nur and carried out the researches on the Lop-Nur and its environment.It was found that in historical period. Lop-Nur has become rich in water, and then with-ered, even dried up for many times. But In modern times, it was not a wandering lake but the salt converging depression of Tarim Basin. As for this point a large area of deep salt rock precip-itated at the center of former Lop-Nur. Tarim River has Changed its route for many times, but it only resulted in the changes in shape of water-surface at the mouth of Tarim River.The area of Lop-Nur has withered for many times, which was related to the development of agriculture in history. About 1400 a BP. and evident withering took place, which was resulted from the route change of Tarim River and cause the ruin of Loulan Ancient city. The drying-up of Lop-Nur in mordern times is the outcome of human influence.In satellite image, there are six evident traces in ancient Lop-Nur and four traces after 1921 can be seen.In consideration of arid climate and human economic development in Tarim Basin the situa-tion of drying-up and desertification can not be changed.