system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do some rivers, like the Colorado, make deep canyons, while others, like the Missouri, don’t?
gpt
as odd as it sounds the Colorado River was a wide lazy river snaking through a wide flood plain like the lower Missouri did (before channelization).  THe big difference is that (here's the mind blowing part), the land around the Colorado was uplifted *after* it became this old lazy curvy river.  As the land uplifted, the river essentially stayed at the same level; carving a valley through the uplifting land that became a really big canyon.