h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

That's correct. Oil exploration does help research more often than I'd like to admit. For example, without it we wouldn't know that the Fountain Formation was Pennsylvanian because it has no fossils to speak of until it grades into a marine formation thousands of feet under the debris in the Denver Basin. So without the drill cores, we'd be blindly guessing.

I didn't comment on your hotspot theory because I've suspected for awhile that the issue relates to the subducted spreadzone, not something similar to the Hawaiian Islands in the middle of the plate but on it's margin. If you look at the volcanism of the Intermountain West it seems to align from north to south and pivot somewhere north of the Snake River Plain. You can follow it through an arc that follows the river upstream to the Tetons fault block then skips into Yellowstone and seems to follow a line all the way to the Bear Paws.

Further south, it seems to originate in the San Juans then follow a similar line to the Rio Grande Rift and it's extensions in the intermontane valleys. The most recent vent appears to be at Dotsero just east of Glenwood Canyon although I understand there are other ones in New Mexico. The Dotsero volcano erupted 4000 years ago.

Further south still, it comes out of eastern Arizona on a very wide line across the Jemez Crater and the San Francisco Mountains then it seems to sweep across the Rift and terminate around Capulan in the north and Valley of the Fires in the south.

In other words, it's huge!

Consequently, I think it would be more accurate to call it a hot field or hot region than a hot spot and it's possible it might still split the continent open sometime in the future. If I'm not mistaken, the Rift is still rifting.

What's the story on the Sea of Cortez and it's northern extensions, like Death Valley?

I'm thinking the San Andreas transform fault preserves not the spreadzone but a prominent fault associated with it and the zone actually trends at an angle more or less northeast under the continent. The transform faults that would have offset the northern portions of the spreadzone have become the Basin Range Province.

That still leaves the question of what if anything may have gone under with the De Fuca plate? Maybe it offset again across northern Utah. That might explain what the Uintahs are doing there.

Here's a quick and dirty sketch of how I think things might be arranged.

http://www.cybercomedia.com/~range/illustrations/zonesketch.jpg

Please note that the offsets would represent transform fault sections if the spreadzone were still in the seafloor but since it's now probably bordering on the mantle, they're reflected in the stretching of the continental crust instead. Also note that this is a hypothetical rendering of the current situation you can trace back west to account for the volcanism that occurred historically like the Snake River Plain, Jemez Crater and similar centers.

Obviously my forte isn't structural but its an idea I've been toying around with for awhile so I thought I'd let somebody take a look at it with a critical eye, because at this point it's a pretty crude and coarse, about like the sketch, and the concept probably needs a lot of work.

Sorry to take so long to reply, I went to Disney's California Adventure on All Saints Day, and have been recovering my fingers.

Wow! This is an amazing idea. I don't know how to go about wrapping my frontal lobes around it. I am used to thinking about plates having convex borders, so the jags you infer would be the sticking point to most people.

As far as the Gulf of California, the San Andreas does take an e/w bend just north of LA called the Garlock fault. This whole sharp eastywesty thing shapes California's coast, and is why most people fail to infer that Reno NV is further W than San Diego CA. The continuation of transverse travel of the SA is presumed to be what is both the shearing off of Baja and the whole horst and graben structures of the Mojave/Death Valley area. Telescope Peak could be considered one huge horst, and having climbed on the trail on that side of it, it's certainly shear enough! It was an ideal place to fly my box kite-even though the trees below were tall, they weren't tall enough to mess with the airflow and eat my kite. The bristlecones on the peak itself were barely two people's worth in height, so they weren't much of an obstruction either.

Maybe we ought to take this to my new Collaborative GeoLab?

http://www.bbc.co.uk/dna/h2g2/alabaster/A866351