N.Wells
Posts: 1836 Joined: Oct. 2005
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Quote (GaryGaulin @ Aug. 06 2016,17:28) | Quote (N.Wells @ Aug. 06 2016,16:46) | Quote | The mountain range I am on is like a miniature version of ones with the world's tallest mountains on them. And likewise what is found around it are fossils and trace fossils that were uplifted, as opposed to having been recently formed on a preexisting mountain range. | No, it's not. The world's great mountain ranges are compressional, due to collisions between plates, resulting in thrust faults, compressional folds, metamorphism, and uplift of the top of the crust and downbuckling of the bottom of the crust. Your mountains (Mount Tom and Mount Holyoke and related ridges) are due to basal heating, crustal extension, differential subsidence, and differential erosion, not compression, and not uplift.
The tops of mountains are carved by a limited arsenal of erosional processes, (mostly frost, root growth, mass movement, and running water, plus glaciation if the mountains are high enough and/or sufficiently poleward). Thus mountains of similar heights and climates tend to have similar-looking surfaces. However, their innards and origins can be very different, depending on how they formed. Yours are quite dissimilar from the Rockies, the Andes, and the Himalayas. Technically speaking, despite being fairly large and rugged, your mountains are more along the lines of homoclinal ridges (loosely, hogbacks) rather than orogenic mountains. |
Well yes, there are differences in how they were formed. The "uplift" at my site is a local event, caused by the tilting of a plate followed by glacial erosion.
Compression also tilts the land, while forcing entire giant plates upwards. But if that were the case for this site then I would more likely be halfway to the top of a Mount Everest type mountain range.
In both cases the fossil bearing formations ended up at a higher altitude, relative to all the rest. |
You aren't getting it.
Hold your arm out horizontally, pointing east. Now lower your hand about 20 cm. Your elbow is now higher than your hand, but that does not mean that your elbow got uplifted relative to your hand. (Your elbow is your house, & your hand is the valley to the east.)
Return your arm to the horizontal, pointing west, and now raise your hand about 20 cm. Your hand is now higher than your elbow, and now I'll agree that you can talk about your hand being raised relative to your elbow. Your top of shoulder would be the rocks in the valley, the underside of your elbow would be your fossil site, and your fingers would be where both formations used to extend to the west, now up in the air. However, this is not what happened to your rocks. You are on a less than usually eroded high spot in a depression, not on a high spot that has been lifted up.
Minor details: No plate tilted here, just the edge of a fault block.
"the fossil bearing formations ended up at a higher altitude, relative to all the rest." No. Your portion of your formation is higher where you are, but you'd have to drill below the younger formation to find it out in the valley. Similarly, if you could go back in time, the younger formation would now be present at elevations well above where your house is now.
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