if the Grand Canyon was created by water erosion from the Colorado river, then how come there isn’t grand Grand Canyons around all or most major rivers?
In: Earth Science
One reason that hasn’t been touched on yet in this thread is — the Colorado is a much “wilder” river than, say, the Mississippi. It is geologically younger, physically shorter, drops farther, and floods more violently and frequently. Hoover Dam, for example, was built only in part to produce electricity — the major reason was flood control, as the flooded Colorado had created the Salton Sea a few decades prior.
Nobody has yet given you the most important reason: **uplift**.
Yes, softish sedimentary rock is important, but if the whole region is not being uplifted by tectonic forces (even far away from plate boundaries, bits of continents can get squished, bent, stretched, fractured, uplifted or depressed), then any rivers flowing through the area will not be cutting down too far before they reach gravitational equilibrium, ie. before they run out of energy to incise into the rock beneath them.
If an area is continually uplifted for a few million years (as much of the American west was), then any rivers are constantly being moved higher than the sea level, so will continue to cut into the rock until they get back to sea level. This has resulted in the deep open canyons to be found all over states like Arizona, Colorado and Utah, especially our friend the most Grandest of Canyons. Canyons can exist without consistent uplift or a permanent river, but soft rock and water in the form of flash flooding is still required and you end up with slot canyons, like [this](https://i.imgur.com/kLhVhRs.jpg) or [this.](https://i.imgur.com/qrkuZS4.jpg)
The river is not the important thing that created the Grand Canyon, it is the type of bedrock. It is rock that is easily eroded by water but still strong enough that it does not collapse and the eroded sediments does not settle in slow moving parts of the river. This have allowed the river to flow through the same path for millions of years and carve out the canyon to its current depth. If you look at other great rivers they usually go through softer soil which means the river banks collapses and the sediments settle so the rivers move all the time eroding the entire area evenly. The Grand Canyon is not the only such geological feature in the world.
The “stuff” that makes up the Grand Canyon was likely more susceptible to fast erosion than that in other areas.
They do, sort of. But the depth of canyons depends on a few things.
To make really deep canyons, you need soft stone that erodes easily (Grand Canyon is lots of loose sandstoney stuff), with a river that flows pretty constantly, in a very geologically stable area. The Grand Canyon area has looked pretty similar for millions on millions of years, giving the river a lot of time to cut a deep canyon.
In many places one or all of these are missing. If the stone’s really hard, the water doesn’t cut well. If the local climate changes a lot, the river can dry up. If the geology shifts, the rive can change it’s course.
And in many places rivers deposit more soil than they remove, regularly flooding their banks and depositing silt that builds up the land rather than cut it.
The river that formed the Grand Canyon was both bigger (aka wider and deeper) and occurred over a much longer period of time than most other rivers.
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