不太可能从侵蚀。有几个原因,而是因为这个过程的时间尺度的发生,其他现象可能完全改变地质情况。峡谷形成的原因首先是因为隆起的构造岩石。从这个页面[1]:>科罗拉多高原的隆起是大峡谷的最终形成的关键一步。板块构造的作用使岩石高而平坦,创建一个科罗拉多河可以减少高原。流失更快,当斜率是陡峭的雕刻峡谷河流量变得温和放缓。所以越深峡谷雕刻,它失去了更多的潜在力量。从同一来源的早些时候引用,地层剖面:[![在这里输入图像描述][2]][2]侵蚀已经显著放缓的另一个原因是,岩石的类型通过多雕刻不同的水更深。河水已经达到了metamorphised层是更加困难比上层的石灰岩和砂岩。 The Vishnu Group is practically bedrock. [This page][3] has a nice explanation: > The steeper the slope, the faster the runoff flow and the more force it will have to move material. The less vegetative (plant) cover and leaf material on the ground, the more open the soil will be to the flowing runoff water. Four things cause slope erosion: the amount and rate of rainfall, the steepness or gradient of the slope, the amount and nature of plant cover, and the type of soil and bedrock underneath. Regarding this question: > why don't we see the mouth of the Colorado (or any river for that matter) gradually move upstream, with ocean filling in where the river once was? Erosion takes material away but this material has to go somewhere. Sediments are carried downstream and deposited at the mouth of those rivers, becoming what we call river deltas. The deltas usually advance **into** the sea as the mass of sediments is incredibly huge. So, to summarize: - There is much less water flowing through now than in the past. If Colorado winters become too mild and dry, then the river's power will be even further diminished. - The slope gradient of the river can only get gentler, so erosion will slow down. - The river has reached much harder rock that resists erosion much better. [1]: https://www.nps.gov/grca/learn/nature/grca-geology.htm [2]: https://i.stack.imgur.com/GOEIu.png [3]: http://www.watersheds.org/earth/field.htm
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