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地球科学日新月异地向前发展,我们有必要了解当今地质科学的新成就和新理论,并对以往的某些认识和说法重新予以考虑.为此,笔者写了此文,供中学师生教学中参考. 地幔的问题 1.软流层的深度.根据现有资料表明,软流层的深度横向变化很大:在中脊裂谷处,其深度极小,几乎等于零;而在一些古老地盾之下,它甚至可能完全不存在,至少已显著变薄.如在北美地台和澳大利亚,一直到300-400公里的深度还未发现它的踪迹.所以,位于上地幔上部的软流层,其下界应到大约地下400公里左右,而不是一般认为的250公里.
Earth science advances with each passing day, and it is necessary for us to understand the new achievements and theories in geoscience today and to reconsider some of the previous understandings and remarks. For this reason, the author wrote this article for the teaching of middle school teachers and students Reference Mantle problems 1. Depth of the asthenosphere According to available data, the depth of the asthenosphere varies greatly laterally: at the mid-ridge rift, its depth is extremely small, almost equal to zero; and in some ancient shields It could even be completely non-existent, at least significantly thinner, as it has not been found in the North American platform and in Australia up to a depth of 300-400 km, so that the asthenosphere above the upper mantle, The lower bound should be around 400 kilometers underground, not 250 kilometers.