Whoa, slow down a moment - geographic accuracy check. While I'll readily concede that the Sierra Nevada looks nothing like Iowa, it also appears nowhere in the movie and furthermore bears not even the remotest resemblance to the fields in the vicinity of Bakersfield, Kern County, California.There are no reasonable explanations for why Iowa becomes like the Sierra Nevada. <snip>
On the other hand: What if... [shatner]What! If![/shatner] ... the quarry really was the size of the Grand Canyon, and it was in the Laurentian System? Not part of any planet or anything, but just this really, really big hole floating in open space? Made of granite or limestone or sandstone or solid neutronium—whatever, really. You could probably fit all of the absent Starfleet vessels in there... and detonate them. Pretty cool, huh?