Late at night in geology bars you are likely to hear all sorts of topics being debated. One of those circles around the questions of just how tall were New England’s ancient Acadian and Taconic Mountains. We talked about them last week when we visited The Mount, Edith Wharton’s old home in Lenox, Massachusetts. The Taconics rose above this landscape about 450 million years ago; the Acadians came along about 50 to 100 million years later. But just how high into the sky did they rise? You can’t tell from what you can see today. Hundreds of millions of years of erosion have reduced their elevations dramatically. The Lenox area lies only a little more than a thousand feet in elevation.
So, how tall were they? Estimates vary. Geologists guess that the Acadians were somewhere between 15 and 30 thousand feet tall. Estimates for the Taconics center on 15,000 feet. We don’t know. But as popular science writers we like the high estimates; they make for better stories. That, however, is not very good science so let’s flesh out the story a bit. The Acadians were the products of Africa colliding with the North America. A similar event today involves the collision of India with Asia. That has resulted in the Himalayas, which are nearly 30,000 feet tall. The erosion of both the Acadians and the Himalayas have produced enormous and similar masses of sediment. The Taconics eroded and produced much smaller amounts. So, we like the Taconics at 15,000 feet and the Acadians at 30,000. It’s an informed guess.
If so, then there is a marvelous thing you can do anywhere in the Berkshires; that’s to look up into the sky and see those ancient mountains, high up above you – five miles above you! Let’s repeat that – five miles! We did that recently when we attended a tea at Ventford Hall in Lenox. Ventford Hall is a gilded-age mansion once owned by a branch of the J.P. Morgan family. Like The Mount, they sponsor lectures, but they also throw in a formal afternoon tea afterwards. We enjoy them and go frequently – last week’s tea followed a lecture about Mary Todd Lincoln.
After the tea, we went out onto the porch on the southeast side of the mansion and gazed upwards – 29,000 feet upwards. We are always aware that every spot on our globe, including Ventford Hall, has a longitude and a latitude. Each one is a pinpoint on the earth’s surface that has been there for 4 1/2 billion years. Sure, we looked up, but we also looked into the past. We looked 375 million years back and, high up there was the peak of one mountain in the Acadian Range. It was a steep pyramid of snow and ice.
Suddenly, we jumped forward through time; it was 430 million years ago. The collision of Africa and North America has been over for about 20 million years, Weathering and erosion of the Acadians had been lowering those peaks rapidly - by geological standards. Those mountains were only 12,000 feet tall. The highest elevations were no longer white and the - were no longer sharp peaks. But they were cut by steep canyons and ravines. There was no sign of any greenery up there. Plant life had not yet evolved an ability to live at those levels.
Then we made another of those leaps through time; it was now a mere 340 million years ago. Our Acadians were now almost eroded away, down to an elevation of about 3,000 feet. We saw a nearly flat, low-level landscape. It was colonized by a thick forest of rather primitive looking trees. They had, indeed, evolved into these levels.
\We stood on the Ventford Hall porch and looked up and saw - no envisioned is the right word - so much of this site’s past. Those mountains were all up there – 30,000, 12,000 and 3,000 feet up. Those pasts have been entirely erased by slow and patient erosion. But not erased from geological memories. Geologists do this sort of remembering all the time.
Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist”. Read their blogs at “thecatskillgeologist.com.”
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