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地貌学山脉的风侵蚀

我很好奇什么山看起来像如果发生几乎完全被风侵蚀。具体地说,我很好奇的花岗岩山会在“雪球”terrestrial-sized xenoplanet。

“雪球”世界,地球是地球大小和保留水中,但外面是太阳的“适居带”,是寒冷的液态水。海洋的冻结深度只有几公里深的口袋保持液体的浓缩矿物质和火山作用。

没有水就没有压裂液体流失,没有冰。唯一的水分在空中将来自升华所以很少冰将沉积在高度和它可能不会形成冰川或造成侵蚀。

低海拔地区,非常缓慢移动的冰川可能会执行大多数侵蚀,但在高空将从风力侵蚀携带水和二氧化碳晶体作为磨料。

在地球上,从水中流失原因凸(广泛的岩石,狭窄的侵蚀通道),而冰川导致凹(狭窄的岩石,宽侵蚀渠道。)硬脆岩石如花岗岩遭受冰压裂留下参差不齐的垂直通道与整体角特性。

在干旱地区地球上侵蚀创建圆角,流体结构像石头的流。但我不清楚多少的一个特性的风蚀和多少软沉积石头的一个特性。它看起来像火星,侵蚀主要是风吹动的,有圆形和锯齿状的山脉比在地球上,但我不知道怀疑那些山脉组成。

如果从风,花岗岩穿它圆滑还是它的内部结构造成骨折甚至没有水?

从另外一个角度考虑,如果地球完全冻结,落基山脉,安第斯山脉和喜马拉雅山脉看起来像只经过几百万年的风力侵蚀?

回答

没有降水山脉是什么样子?在地球上我们有一个很好的例子:纬度之间的安第斯山脉,17岁和30度。这些山脉不是花岗岩,但它们是火成岩和meta-igneous岩石,类似的水晶。山的东部斜坡上被水浸湿,在亚马逊流域蒸发。西边是阿塔卡马沙漠。例如,玻利维亚首都拉巴斯,坐落在东部丘陵地带,每年降雨量500 - 600毫米。相比之下,智利阿里卡市——只有350公里——接收平均0.08毫米。这是谷歌地球视图之间的安第斯山脉阿里卡和拉巴斯指针在大陆分水岭(这不是最高点,我巧合的是运行在一个峰会在玻利维亚行)。[!(谷歌地球的安第斯山脉之间阿里卡和拉巴斯][1]][1]我们可以立即放大山上降水的影响。 **The highest summits: No precipitation means no glaciation** Fig. 1 is a close-up of two high Andean peaks which appeared in the photo above: the gorgeous, volcanic 6310m Parinaquta on the eastern slopes [Fig. a left], and the rugged 6350m Illimani on the west [Fig. a right]. Illmani has been deeply glaciated, as have most high summits around the world. Its flanks are cut by U-shaped valleys. Its summit is surrounded by steep glacial headwalls. When those headwalls retreat, the summit will collapse. Parinaquta, in contrast, has clearly never held much ice (though a little snow still clings to the summit - nowhere on Earth is entirely dry). The dominant texture on the mountain is not caused by glacial valleys, but by individual lava flows. The mountain has good radial symmetry, like volcanoes on Mars. It will continue to grow for a long time yet. [![enter image description here][2]][2] **Middle elevations: strangely straight channels** Let's take a look at the dry side of the Andes at lower elevations. Fig. b shows a 30-km area located halfway between Parinaquta and Arica. These channels are quite unusually straight. No quantitative work has been done on these channels to the best of my knowledge (at least in the English scientific literature; Chilean geologists may have done much more). Morgan et al. (2014) assert that these channels are formed by mud-rich flows. These wet flows are few and far between. The majority of the sediment is moved by air. The wind in the area flows preferentially through the channels, but - unlike the mudflows, or normal rivers - it is driven less by downhill-gradients than by large-scale weather gradients in the area. The wind flows straight, and it straightens the channels. [Morgan et al. also suggest that, during particularly dry periods, the wind may leave channels in inverted relief]. **Coastlines: dry climates don't erode much** Your question does not directly mention coastlines, but the dry Arica coast does have one relevant feature: the river mouths do not have noticeable deltas. The volume of a delta is a rough proxy for the rate at which sediment is removed from the mountains upstream and carried out to the ocean, minus the rate at which the ocean carries sediment away from the shore. This proxy has limited value, as it is greatly affected by ocean dynamics, the drainage area of the river, and the presence of a subduction zone near the shore. Most wet coastlines with subduction zones (such as the coast of Papau New Guinea, Fig. c left) produce enough sediment to maintain estuaries, deltas, or little puffs of sand. In contrast, the rivers near Arica hardly change the shape of the Chilean coastline (Fig. c right). We can predict that a reduction in total precipitation on the Earth would drastically reduce the average erosion rate on land. **Global changes** Earth, unlike Mars, has active tectonics. Our volcanoes will never grow to the height of Olympus Mons because the continental plates shift beneath them. Yet our mountains now are beset by river incision and by glaciation. Their lifetime is short - perhaps half a billion years, no more, and usually far less. Wind erosion is ~one hundredth the speed of glacial and fluvial erosion. On Dry Earth, a mountain range might survive to be nearly the same age as the planet. If tectonics were to carry on at their usual rate, mountains would soon cover much of the Earth. Sedimentary rocks would be rarer, and made of baked dust rather than river cobbles or mud. Needles of salt might grow on the plains, if there was enough moisture for the air to carry them. I imagine Dry Earth as a towering desert, where the lowlands are walled in by the broken remnants of billion-year-old mountain chains, and the dust is made from dark volcanic rock. [1]: http://i.stack.imgur.com/TseCS.jpg [2]: http://i.stack.imgur.com/cGili.jpg

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