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当沉积物沉积时,他们陷入地球吗?

我在听一个地质播客描述沉积岩形式如何,后来变成了变质岩。作为河流铺设了沉积物,下层最终可以在地下几公里,热量和压力意义重大。

这是如何发生的?河床的建造越来越高,直到第一层沉积物埋藏深,还是底层下推到地球吗?换句话说,是给定的河流段的高度增加而发生这种情况,还是保持不变?

回答

不,沉积物不沉入地球因为它们太轻。他们表面上很长时间形成的大陆。但他们可以埋在许多公里的其他沉积物的部分地壳他们消退或被推倒在其他地方。因此他们可以进入压力/ temperatue条件,成岩作用(见其他回答)或(变质)[1]改变它们。在一般水平,板块构造使地壳运动。它可以导致表面某些地方和消退。当它上升形成山脉,例如在一个(造山运动)[2]在一个俯冲带或当两大洲之间的碰撞和地壳被迫向上。(风化)[3]和[4](侵蚀)开始上升区,和它们产生大量的沉积物所运送水、风和重力分解成较低的地区。Otoh,地壳拉伸或消退,如在[地堑][5]或[盆地][6],沉积物中积累,一层一层地,告诉的长故事发生了什么事在过去(见@Universal_Learner的回答)。另一个,更奇异的过程形成厚沉积物包,是海洋沉积物的刮掉从俯冲板块形成一个[增生楔][7]。 These sediment packages can get many kilometers thick, the [Pannonian basin][8] holds the sediments of a mountain range in thicknesses between 1 and 5 km, >6km in the [Molasse][9] basin north of the alps, up to 16km in the [Upper Rhine Graben][10], where they can be altered metamoprhically (apart from contact or hydrothermal metamorphosis in regions with volcanism). Metamoprhic conditions ("facies") can also be met in a continent-continent collision and the connected mountain ranges, like parts of the [Himalaya][11]. Rivers (i am not an expert in this and kindly ask for correction) do not rise above the surrounding (gravity is against it ;-)), but they change shape and appearance with the slope and sediment load. For example from "[alluvial fans][12]" at the foot of a mountain over "[braided rivers][13]" in mountainous areas where slope is still high and grain size big over [meander][14] patterns in low slope areas with small grain size to [deltas][15] filled with mud and clay. When a river reaches an area where it can't carry on because all around the land rises again, it can build a lake until it finds a new exit, or it simply fills up the area with its sediments. [1]: https://en.wikipedia.org/wiki/Metamorphism [2]: https://en.wikipedia.org/wiki/Orogeny [3]: https://www.scientificamerican.com/article/weathering-rocks/ [4]: https://www.nationalgeographic.org/encyclopedia/erosion/ [5]: https://en.wikipedia.org/wiki/Graben [6]: https://en.wikipedia.org/wiki/Foreland_basin [7]: https://en.wikipedia.org/wiki/Accretionary_wedge [8]: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015TC004109 [9]: https://en.wikipedia.org/wiki/Molasse_basin [10]: https://ui.adsabs.harvard.edu/abs/2005IJEaS..94..732S/abstract [11]: https://www.geo.fu-berlin.de/en/v/geolearning/mountain_building/metamorphism/generation_types_metamorphism/collision_metamorphism/index.html [12]: https://en.wikipedia.org/wiki/Alluvial_fan [13]: https://en.wikipedia.org/wiki/Braided_river [14]: https://en.wikipedia.org/wiki/Meander [15]: https://en.wikipedia.org/wiki/River_delta

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