re: Crater Lake
What part of "it's a hole in a mountain" don't you get?
Lake surface is typically 6200 feet; lake bottom is thus 4300 or so. The top parts of the caldera wall are around 8000. The surrounding land, i.e., once you're off of the remnant volcano (Mt. Mazama) is around 4000 in the lava plains on the east side, or a couple of thousand for the valley floors in the dissected old volcanics (Western Cascades) to the west.
Trust me, I've been there and know the Cascades well. Crater Lake is a big mountain made of silica-rich volcanics that has been hollowed out. If you want to argue it as an analogue for a 700 meter wide hole in a sedimentary plain, go right ahead