system
Given the following post, respond as if you're commenting on Reddit:
human
Why is the Congo River so deep?

I just read that the Congo River is, like, 220m deep. The Nile apparently is only about 8 to 11 m deep on average. And it is double the Amazon's 100m. 

I mean 220m is basically the depth of Lake Huron. Motherfucker is *DEEP*.

But ... why?
gpt
Well the short answer from the quoted paper where that measurement came from

 "The channel is more like a high-gradient mountain stream with a very 
large discharge; which is consistent with the theory that a short mountain river eroded 
through the divide and reached Malebo Pool, forming the present Lower Congo 
River. " 

This is the location where that measurement came from.

However reading the rest of it, this is an anomalous depth and the majority of the river co forms to more normal standards and is around 10 to 80m on average.