This is Wallula Gap, where the Columbia crosses this roughly EW ridge, itself called the Horse Heaven Hills on the west side. The ridge is one of the famous (in geologic circles, anyway) Columbia Basin anticlines, where the basalt layers have been buckled up by large-scale compression oriented N-S. So, this is a classic antecedent drainage, where the Columbia kept cutting its channel while the land rose around it.

We lived in Pasco in the late 80s, and our son was even born there, so this is familiar country! My wife was the USDA's Inspector in Charge at a large meat plant between Pasco and the turnoff to Walla Walla.

So you saw the Columbia cut through yourself! That must have been amazing.... (I'm teasing). As I've said before, it would probably be interesting to travel with you and see all of this through your eyes/knowledge.

I'm guessing you've been back to Pasco. I was surprise at the amount of suburban sprawl out there, too much of looks just like any other 'cookie-cutter' suburban growth.