Wednesday, April 26, 2017
South Slope 7th Avenue Glacial Erratic...Is it a Bear or a Dog?
Contrary to current political beliefs, there was a time in history when snowflakes wielded immense power to shape the Earth's crust, scouring the world's surfaces and literally moving mountains from their path. For a long time favorable temperatures existed allowing these snowflakes to pile up to levels that dwarfed all of existence even forcing sabertooth tigers and wooly mammoths to forget natural animosities and band together to escape the oncoming destruction in search of a more tepid paradise.
These accumulated snowflakes were compressed into sheets of ice miles thick and immensely heavy that eventually, with the help of gravity, began to inch downhill pulled to the center of our universe, my backyard, Park Slope... South. As this great ice shelf moved forward it plucked boulders from upstate bedrock and transported them piggyback style until there came a time when they didn't and then they dropped them. These traveling boulders are known affectionally among rock nerds as "Erratics".
This rolling stone surfaced during a recent excavation to repair/replace a section of sewer line under Seventh Avenue. Glacial erratics of coarse are found throughout the 5 Boroughs of NYC. Brooklyn's entire topography is essentially a vast tailings pile of eroded mineral debris left behind by retreating deadbeat ice flows. It's we just don't think about 'big rock' until the entire city block's discharged fecal matter starts backing up into our basements due to collapsed geriatric sewer lines and then the blacktop has to be opened revealing...rocks and really dirty stuff and nature.
Eighteen thousand years ago when New York State's Laurentide Ice Sheet began to stop flowing, resting, then began receding, it dropped what is essentially a Long Island's load worth of degraded rock, sand, and clay behind, "Till, they call it. Glacial till!"
Erratics throughout time have been given prominent positions in our society, often indeed named and given spiritual powers. For a nicely arranged collection of erratics, one has only to travel as far as Prospect Park and visit Rock Arch and Boulder Bridge. A secluded part of The Ravine's waterway where one can sit alone, hopefully unsolicited, for awhile beside Ambergill Falls and ponder just how far, like a glacial erratic, you have traveled in your life's span before coming to rest in your current position amongst the geologic silt stratum that is NYC.
So is it a bear or is it a dog?