posted by swishfish at 16:51
Justin Green, you are a geologist. Therefore, you may be able to answer my question. If two mountain ranges are side-by-side, how do geologists tell whether they are different or the same mountain ranges? For instance, I was looking on the map as I was passing through Pennsylvania and noticed that the Appalachian Mountains are right next to the Allegheny Mountains. How do they know they're separate mountains and not part of the same chain?
The strict defenition of a mountain range would be an area of land that was raised into mountains, so everything in that area is really part of the Appalachian mountain chain, which was formed in its present form by the Appalachian or Alleghenian orogeny (orogeny means mountain building). Looks like the sub-divisions of the mountain chains is based upon geological reasons, such as type of rock, fault-lines, and the type and amount of folding that has happened.I'm afraid that I'm not an expert on American geology, so apologies for the vagueness...Interestingly, the "ancestor" mountain chain along the east of the US is the same mountains that are found in Ireland, west Scotland, and Norway. About 400 million years ago the north of Scotland (basically the Highlands) was part of teh American plate, and a large mountain range. The mountains are smaller (Scotland and Ireland) or bigger (Norway and the US) depending on the erosion that has taken place since, such as ice ages. So the mountains in the Eastern US and here are essentially the same mountains.
PS sorry if that was a bit dry...
The slow internet connection in this hotel in combination with me trying to download some audiobooks for the drive tomorrow (making the connection speed even slower) prevents me from actually looking at the links you've linked to, which might help explain more stuff. I actually expected your response to be more dry than it was in actuality. I have a number of friends who went to Caltech (one of the top math/science schools in the US) and am used to hearing dry explanations, but I think it's cool and interesting. Probably because my ring fingers are longer than my index fingers.
PS: I really don't understand why it usually takes me two tries to get your word verification lettering correct, whereas on other sites I get it the first time. Frustrating!
I set mine to "extra hard" to filter out undesirables...
So I am on the edge of being undesirable! I suppose I can deal with that, since I am always given a second (or third!) chance to be allowed in the "in" crowd.
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