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是河道时形成海底陆地海拔?

在这个卫星图片,在陆地上哥伦比亚河北美西部的一面。

我吃惊的是,看到海洋内的通道,125多公里长。

可以得出结论,仅根据这幅图,这个频道成立的全部是海拔?换句话说,是已知最合理的机制的形成这样的海底通道?
它还可以得出的结论是,左边的通道,它分为三个分支,与古代古三角洲海岸进一步向左?
海底通道是什么原因开始数万公里远离目前的海岸?过去,通道会扩展直到现在河的嘴,然后填满了沉积物在以后几千年?

回答

>可以得出结论,仅根据这幅图,这个频道成立的全部是海拔?换句话说,是已知最合理的机制的形成这样的海底通道?在这种情况下。虽然一些海底峡谷形成海平面更低时,阿斯托里亚峡谷,你问什么,不是其中之一。现在的例子是什么海底峡谷但被河流雕刻海平面较低时包括地中海海底峡谷。地中海几乎干涸时切断从大西洋大约600万年前。这导致河流尼罗河切割等长的峡谷,后来被淹没。阿斯托里亚峡谷呢?[!(阿斯托里亚峡谷深度等高线图; see description below][1]][1] <sub>Image source: https://oceanexplorer.noaa.gov/explorations/lewis_clark01/background/geology/geology.html</sub> As seen in the above counter plot, the Astoria Canyon starts at about 200 meters below sea level, at the end of the continental shelf, and carries on to the bottom of the continental rise. Sea levels fell by about 125 meters at the peak of the last glaciation, so it wasn't a river carving a canyon in land that was above sea level at the time. This does not mean that the Columbia River did not play a role in the formation of the Astoria Canyon. One of the leading hypothesized formation mechanisms of the Astoria Canyon is the huge amounts of sediment deposited by the Colorado River from the multiple Missoula Floods that resulted from the breaching of ice dams that formed massive glacial lakes in western Montana during the latest glaciation (and possibly during previous glaciations). These floods scoured eastern Washington, creating the Channeled Scablands. Those sediments were then deposited past the mouth of the Columbia River. Turbidity currents carrying those sediments then scoured their way down the steep continental rise -- but not the much flatter continental shelf. [1]: https://i.stack.imgur.com/guHN6.jpg

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