Re: Renaming Europe

Patricia C. Wrede wrote:
"J. F. Cornwall" <JCornwall@xxxxxxx> wrote in message news:dWUHf.3332$Nq1.981@xxxxxxxxxxxxx
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Would have to postulate something like the heat source for the East Pacific Rise extending further north than in our world, so there is a mechanism to provide energy to heat the continental crust and turn that world's Gulf of California into an extensional rifting zone instead.

Hmm, that would also be likely to have changed the subduction rates and history elsewhere along the western edges. At least for the southern "USA", not having a subduction environment would mean no recent mountain-building episodes, so the Sierra Nevada would be more like the Appalachians (worn-down, eroded to lower heights, no large volcanic peaks such as Mt Lassen, etc). Volcanic mountains would tend to be smaller cinder-cone types, or basaltic shield volcanoes (Hawaiian type). Other ecological variations would follow from these. One of the major thoughts on how we came to be human depends on climate changes in the East African Rift Valley. Maybe the Western North America Rift could give rise to your alternate ecology. :-)


What does that do to the Rockies? If it's a choice between them and the California Channel, I'll probably keep the Rockies. I don't mind having different mountains, and more active volcanoes would be kinda neat (and possibly useful; they do seem like a possible environment for dragons, and certainly a good one for salamanders and perhaps firebirds and phoenixes).

Patricia C. Wrede


Hmm, well... The Rockies were built more by compression and folding than by volcanism. You could still get these sorts of forces acting on the N.A. plate, raising the Rockies before the advent of a rift zone in California. http://wvcweb.ctc.edu/rdawes/FocusPages/PNWorogenies.html gives a sequence (no solid timeframes attached, but then we tend to be a little fuzzy about those anyway in geology :-)). Basically you'd have the oldest mountain-building event, the Laramide, raising the ranges. The younger events, creating the higher volcanic ranges, might not take place, so you would get no Cascades or Sierra Nevada.

Given the lack of younger orogeny events, the mountains will be more eroded, shorter, more rounded, and would be likely to consist of the tough crystalline rocks that have survived tens of millions of years of erosion. Very much like the Appalachians - gniesses, schists, granites, and the like. Probably a well-developed system of old, resistant ridges with a trellis-like pattern of river valleys that have managed to cut thru the ridges at gap points (like the Cumberland Gap), and relatively few breaks other than these.

The "Basin & Range province" of the southwestern US would be unlikely to exist, or if it had developed at one time its growth would have been stunted by the development of the western rift zone. This is because the basin & range type terrane is a feature of continental plates being pulled apart, and this would not be taking place. Instead of the friction with the Pacific plate dragging a big part of the N.A. plate northwest, the rift zone to the west would be essentially pushing the area back against the N.A. plate. I don't know if that would be enough push to create mountains, but it ought to prevent the extensional faulting. Result: the area which today is a series of alternating ridges and valleys would be something different. "The Great American Desert" might be a fertile plain instead...

Just a few speculations. This is fun. :-)

Jim
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