Friday, February 20, 2009

Day 245: Rocks of ages

views from prospect park this morning (click to enlarge)

I have been running in Prospect Park for 7 years. Today I after I completed my loop I paused to take a look around. 50,000 years ago the area that makes the park was buried under a 1,000 foot sheet of ice. When the ice retreated these rocks were left behind- about 20,000 years ago!

"We detoured through Prospect Park, which is nestled into the morainal front and is studded with big erratics on raucously irregular ground. It looks much like Pokagon Park, in Indiana, with the difference that the erratics there are from the Canadian Shield and these were from the New Jersey Palisades. Pieces of the Adirondacks have been found in Pennsylvania, pieces of Sweden on the north German plains, and no doubt there is Ticonderoga dolomite, Schenectady sandstone, and Peekskill granite in the gravels of Canarsie and the sands of Coney Island. But such distant transport, while it characterizes continental ice sheets wherever they have moved, accounts for a low percentage of the rock in glacial drift. The glacier cuts and fills. Continuously, it plucks up material and sets it down, plucks it up, sets it down. It taketh away, and then it giveth. A diamond may travel from Quebec to Indiana, some dolomite from Lake George to the sea, but most of what is lifted is dropped nearby -- boulders from New Jersey in Prospect Park...

...When she looked up at the Empire State Building
, she was unaware that it owed its elevation to the formation that outcropped in Central Park; and when she saw the outcrops there, she did not wonder why, in the moist atmosphere of the American East, those great bare shelves of sparkling rock were not covered with soil and vegetation. In Wyoming, wind might have stripped them bare, but Wyoming is miles high and drier than the oceans of the moon. Here in the East, a river could wash rock clean, but this rock was on the high ground of an island, far above flood and tide. She never thought to wonder why the rock was scratched and grooved, and elsewhere polished like the foyer of a bank. She didn't know from geology...

...Now when she goes up Fifth Avenue -- as she did with me that summer day -- she addresses Fifth Avenue as the axis of the trough of a syncline. She knows what is underfoot. She is aware of the structure of the island. The structure of Manhattan is one of those paradoxes in spatial relations which give geologists especial delight and are about as intelligible to everyone else as punch lines delivered in Latin." -excerpted from John McPhee's 1983, In Suspect Terrain reproduced in PBS's The Center of The World.

Learn more about the geology of Prospect Park from the Prospect Park Alliance.

** fun facts from the Alliance:
"Prospect Park is also the site of the last remaining indigenous forest in Brooklyn."

"At nearly one mile in length, the Long Meadow is thought to be the longest stretch of unbroken meadow in any U.S. park"

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