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a human and glacier shaped terrain
FOP made a field-expedition this weekend to Prospect Park. It turns out, during the Pleistocene the neighborhood park was the site of a 1,000 ft. high ice sheet.
From the Prospect Park Alliance website,
“Although many of Prospect Park’s landscape features were man-made, the Park has geology to thank for much of its natural beauty. Fifty thousand years ago – in a period known as the Pleistocene Epoch – the land beneath the Park was buried under a sheet of ice 1,000 feet thick. During this Ice Age, North and South America were submerged under slowly shifting glaciers. In the vicinity of New York, the Wisconsin Ice Sheet crept slowly south, dragging along detached bedrock, sediment, clay and soil.
When the climate began to warm 20,000 years later, the ice retreated, leaving a belt of hills (known as a terminal moraine) that runs through Queens, Brooklyn, and Staten Island. The northern edge of Prospect Park lies on this ridge, on land too steep for easy farming but well-suited for a Park complete with rich woodlands, steep ravines, and hilly meadows. The southern edge of the Park was built on crushed rock and gravel left behind by the melting glacier. This outwash plain would one day serve as the site for Prospect Park’s 60-acre Lake.
The Wisconsin Ice Sheet also left behind depressions in the land known as “knob and kettle terrain.” These “kettle ponds” formed the geological surface necessary to create the Park’s watercourse, beginning with Fallkill Falls and continuing into the Ravine, Lullwater and the Lake.”
We took the Park’s information and calculated that the ice that ground its way to the northern boundary of Prospect Park towered above the Grand Meadow to a height just under that of the Empire State Building (102 stories / 1,250 feet).
ice levels in the park have greatly receded in recent years
after the urban ice melt on 1.09.10
We projected our imaginations into the Pleistocene through the contemporary landscape, and arrived at this speculative image of the Wisconsin Ice Sheet rising above the park. A 1000 ft thick ice sheet would exceed the height of the apartments surrounding the park by roughly seven times their height:
Prospect Park's glacial imaginary
(Photo composite by FOP with special thanks to Alan Vernon for his Creative Commons glacier image)
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