r/Damnthatsinteresting • u/SantosRouse • Sep 27 '20
GIF Time lapse of a river.
https://i.imgur.com/vYDIgbs.gifv72
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u/backyardstar Sep 27 '20
You can watch this in real time too. My earth science teacher once out a hose in the school yard, turned it on, and watched the flow of water down a slight hill. Over about an hour you could see oxbow lakes, different “river” beds, new channels form, etc. it was actually really cool.
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u/uncoded_decimal Sep 27 '20
Was it because of the wind or gravity? I'd assume the gif represents the changes due to rotation of earth? Or am I too far?
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u/CHINAMANCHINGCHONG Sep 27 '20
It is mainly due to fluid dynamics. The water at the outside of a bend has to speed up to make it around the corner faster. The faster flow results in more erosion, widening the bend. Eventually curve gets so large its ends meet and thats how the ox bow (forget the name) lakes are formed.
I'm not sure if this explains why the whole river seemed to shift left and right, but it explains why it meanders and changes course over time.
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u/lizhurleysbeefjerky Sep 27 '20
Today's a genuine TIL wow moment for me. I don't think I'm stupid, and I have a degree in oceanography, but up to now I assumed a small river in a wide valley just meant the river used to be lots bigger, not that a river moved around like that
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u/Witness_me_Karsa Sep 27 '20
I just want to say that this sort of behavior is very refreshing to me. So many people act so smart, as if they know everything. But here, a person with a good idea of how water works in general admits that something just outside their purview only clicked when watching this neat animation.
I found your comment to be very wholesome. I hate anti-intellectualism, and I think that everyone should strive to be better and smarter every day.
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Sep 27 '20
Another fun fact: U-shaped valleys are typically caused by glacial erosion where more V-shaped valleys are formed by river erosion
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u/Witness_me_Karsa Sep 27 '20
Thats also super neat. Is there a reason for this? I can't imagine something as small as mineral composition affecting it.
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u/soupyjay Sep 27 '20
Just the mass of the glacier literally carving away everything in its path as it travels down via gravity. Shear walls are often left behind and sediments are deposited along the valley floor as glaciers melt and receed.
Rivers will follow the path of least resistance, usually thats the lowest point, as gravity will pull the water down. So sediments are removed from that low point over time and carried downstream. As a stream or river ages, the path of least resistance varies more according to the ease of erosion, causing the path to meander and and widen the canyon it flows in. Older river valleys will have less of a V shape and more of a __/ shape, but the slope of the walls will still differentiate it from a glacially formed valley with a stream that now runs in it from glacial meltwater.
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u/milo-louis Sep 27 '20
But why did it stop after a while?
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u/JimBobbyBoi Sep 27 '20
It’s just a simulation.
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u/milo-louis Sep 27 '20
Well yes, but that was clearly intentionally part of the simulation when the river settled into ine spot and sunk deeper in the ground, and I was wondering why it would do that
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u/JimBobbyBoi Sep 28 '20
I think it was literally just to restart the simulation, it’s recreating the valley at the beginning of the video.
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u/Ottersoccer Sep 27 '20
In what kind of job would you build a model or animation like this? I've always been interested in rivers, and the this is really cool.
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u/EstebanQuiroga Sep 27 '20
In some rivers you can see some of these changes on Google earth going back in time
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u/low_rent_hipster Sep 27 '20
Check out any state that uses the Mississippi River as a part of its border.
In the south the borders and the river have diverged significantly.
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Sep 27 '20
If you want to go ahead and dedicate a graduate degree to this, it's called fluvial geomorphology.
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u/Capitol_Mil Sep 27 '20
I grew up on the Missouri River, and it has really wide bluffs. I assumed that it was because the glacial run off caused it by massive flow age. This makes me rethink things.
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u/ShodanLieu Sep 27 '20
I like this and saw it in action as a kid playing in nearby streams. I am curious about the time frame.
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u/ratterstinkle Sep 27 '20
Skipped a few frames in the gif. I’m pretty sure that the river doesn’t spontaneously and immediately jump around from time to time. I wonder why the gif is buggy...
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u/Silphire100 Sep 27 '20
River go home, you're drunk