Another geologist checking in here… Pantellerite’s got some good links up there and don’t let the flatter nature of the structure fool you. The mineral composition of the magma might account for that OR it could be from a post-eruption collapse due to depletion of the supporting magma chamber.
Well, I’m sitting here with my DeLorme Northern California Gazetteer on my lap. Mt. Shasta is on map 36, at A-4, but it’s really all over the place on the dividing line between maps 36 and 37. It’s huge.
So about 45 miles east of that is map 38. In the top middle of map 38 at A-2 is something called “Deep Crater”, directly abutting the south edge of the Burnt Lava Flow Virgin Area [notice with what incredible self-discipline I avoid making the obligatory joke about virgins].
“Deep Crater” itself measures only about a mile across, it has only two elevation lines, and it’s surrounded by flat scrub. I think it’s too small to be a caldera. For comparison, Mt. Shasta takes up nearly my whole Bic pen, with at least 20 or so closely spaced elevation lines, which makes it, ooh, really big, sprawled there in between maps 36 and 37.
But “Deep Crater” is only half an inch wide, making it a mile across, and it’s flat around it. And yep, it sure does look like an impact crater with a nice berm around it.
Geobabe?
These are the coordinates for maps 38 and 39, spread out open across my lap.
Top latitude is 41[sup]o[/sup] 30’.
Bottom latitude is 41[sup]o[/sup] 00.
West longitude is 121[sup]o[/sup] 45’.
East longitude is 120[sup]o[/sup] 52’ 30".
So Deep Crater is up in the very top middle of map 38, almost right at latitude 41[sup]o[/sup] 30’, shoulder-to-shoulder with the lava beds.
That sounds like what I saw. I think I remember guessing the crater I saw was about a mile across, but it has been three and a half months… How long is a mile as viewed from 30,000 feet?
You didn’t notice another round crater several miles north of there, did you? IIRC, it wasn’t as “neat” as the first. A little more ragged.
Dang! Every time I try to use that topozone site, byt browser crashes! Fortunately I took the precaution of clipboarding the top part of this post!
So anyway… Any craters north-ish? I was leaning toward caldera until Duck Duck Goose aggreed that his topo chart looks like an impact. I was thinking that if there were other craters within 20 miles or so, and if they were progressively smaller, that it might indicate a strike. (Not an astrophysicist either, but I’m guessing the larger pieces of a broken meteorite would hit first.)
[QUOTE]
*Originally posted by Johnny L.A. *
**
Um, yeah, actually there is, now that we’re over the “getting home from school” chaos and I can sit here with a gazetteer in my lap without having to explain 40 times in a row what I’m doing.
On map 28, which is the map directly above map 38, just at the bottom edge of the map, right on 41[sup]o[/sup]30’ latitude, in the middle of the Burnt Lava Flow Virgin Area, about 3 miles directly north of “Deep Crater”, it says “High Hole Crater”, but there aren’t any elevation lines, just a big round blob of green-for-trees, which I take to mean that the blob is a slightly sunken depression that filled with soil and moisture and can support trees. Bear in mind that in this neck of the woods, “trees” can mean some pretty scrubby-lookin’ little things, so from the air you might have been able to see it as an impact crater. It’s about a mile wide, too.
If you keep going due north about 10 miles, you run into Lava Beds National Monument.
…and squinting at it here, I see that there’s a kind of smaller ragged blobby extension due north of the round green blob. So viewed from 30,000 feet it might have looked like one ragged crater.
(love these technical terms–“ragged blobby”) 
From what i’ve seen of Long Valley caldera (i know this isnt the one but for example’s sake), it doesnt look like it’s a volcano. It’s about 18 miles across, but it does have smaller cones inside of it (part of the mono-inyo chain). When Long Valley caldera blew, it was 2,000 times stronger than the Mt. Saint Helen’s eruption.
Take a look at this, is this it? This seems to be what DDG was talking about.
http://terraserver.homeadvisor.msn.com/image.asp?S=14&T=1&X=194&Y=1435&Z=10&W=2
Genseric: Good link! I can’t really say that’s what I saw, though. I guess I’ll have to take a ride on Alaksa Airlines and bring my camera next time!
This just occurred to me: Could circular depressions be caused by geysers (or old geezers 
)? Maybe I saw an old mud pit?
Still nuttin’ but thanks for thinking of me. Got any questions about the geology of New England?
I don’t think so - none that were a mile wide or so, at any rate. I wouldn’t want to be around if a geyser that big ever blew. Given the geologic activity in the area, I would still favor a volcanic crater of some kind - they don’t all have to be as big as the one at the top of Mount Shasta. The only other possibility that springs to mind is the opening marking the collapse of a lava tube, although what you saw seems a bit big for that as well.
I think you’re just going to have to fly over it again and report back. 
The Cinder Cone at Lassen Park
Although it’s probably not the one you’re referring to,there is an amazing cinder cone In Lassen Park’s eastern backcountry.
I have hiked there and gone to the top.
It looks just like what every volcano in every Tarzan movie or dinosoar movie always looked like.It is barren,perfectly cone shaped with a flat top,and a cone shaped crater.
Also notable are the surroundings."Painted"dunes of brightly colored volcanic cinders,a large grey desert of the same,and a huge jagged lava flow(shards of rock)called “The Fantastic Lava beds”.