The glacial erratic known as Patterson’s Pellet. (photo by John Hayes | courtesy of the Mohonk Preserve)
For nearly 20 years now, the Shawangunk Ridge Biodiversity Partnership has offered a winter lecture series, “Secrets of the Shawangunks.” Held every Thursday evening in February — when temps outside can be too cold to experience nature firsthand — the events are free of charge to attend and no advance registration is necessary. Topics covered in the presentations are different every year and cover a broad spectrum of biodiversity on the Ridge, from wildlife to forest dynamics to land use planning.
Judging from the size of the overflow crowd of people ranging from 20-somethings to seniors at the first lecture last Thursday, the word is out. It was literally standing room only in SUNY New Paltz’s 234-person capacity Lecture Center, room 102, as Dr. John A. Rayburn, associate professor of environmental geology and geomorphology at the college, took the mike to present “Glacial History of the Catskills and Mid-Hudson Valley: Setting the Table for our Region’s Ecology.”
Dr. Rayburn was an engaging speaker, enthusiastic about his subject. He showed the audience photographs of fractures and gouges in the rock surfaces on the Ridge that prove glacial activity formed the local landscape. “And if you walk along the Ridge,” he said — or any place in New York State from the Adirondacks to the Catskills — “wherever there is exposed rock hard enough to retain these records, you can start putting together a map of where the ice went and what direction the ice flowed.”
Using a series of illustrations and diagrams, he invoked the principal of uniformitarianism — “everything in the past works the same way it does today” — to explain the process by which geologists determined that an enormous sheet of continental glacial ice flowed south like a viscous river from the Northern Quebec area thousands of years ago, bending in some places and altering its direction, carving out the land.
Uniformitarianism was first articulated by Scottish geologist James Hutton (1726-1797) to explain the features of the Earth’s crust by means of natural processes over geologic time. In other words, since we can assume that in the past, “a raindrop falls, gravity works and streams flowed downhill” just as they do today, said Rayburn, a geologist can compare known records from the geological past and apply these natural principals to try and figure out how something we see today happened.
And a glacier is not just any big chunk of ice, we learned. “A glacier, by definition, is a long-lasting ice mass formed upon land,” — with emphasis on the land, Rayburn noted; a glacier can’t be sea ice — “that moves under the influence of gravity and its own mass. It must be moving. If it’s not moving under its own influence, it’s just ice.”
Early geologists thought that it was Alpine glaciers that formed the landscape in New York, he said, but they know now it was a vast sheet of continental glacial ice, which worldwide, today, is much more common than mountain-like Alpine glaciers.
The recipe for a glacier to develop demands a climate with a cold summer, Rayburn said. “You need land, you need snow, but the critical part of the recipe is having cold summers. To pile up the snow, you need it to last throughout the year so you can pile up more snow the following winter, and so on. And you need gravity, because by definition it has to move under its own mass by the influence of gravity. Finally, time. It takes time to pile up enough snow to turn it into ice and have the ice reach the plasticity in which it can move under its own mass. That’s how you make a glacier.”
The winter lectures are co-sponsored by the SUNY New Paltz biology department. The Shawangunk Ridge Biodiversity Partnership is a coordinated effort founded in 1996, made up of the New York State Department of Environmental Conservation and Office of Parks, Recreation and Historic Preservation, the Nature Conservancy, the Mohonk Preserve, the Open Space Institute, the New York Natural Heritage Program, the New York State Museum, the Palisades Interstate Park Commission, the Cragsmoor Association, Friends of the Shawangunks, the U.S. Fish and Wildlife Service and the New York/New Jersey Trail Conference.
While the organizations work together across the boundaries of their properties to manage the landscape as a unified whole, with a range of organizations as varied as these, the lectures reflect a lot of different interests.
Next up in the series, also presented at SUNY New Paltz’s Lecture Center, room 102, will be “Reviving the American Chestnut” with Dr. Allison Oakes on Thursday, February 9 from 7-8:30 p.m. (NOTE: This event was cancelled due to the snow storm.) Dr. Oakes is a post-doctoral research associate in plant science and biotechnology at SUNY College of Environmental Science and Forestry. In the 19th century, the American Chestnut tree was the predominant tree species in eastern forests, but a blight in the early 20th century made it extinct by the 1950s. Oakes’ presentation will reveal the encouraging results of scientific efforts to resurrect the once-great tree species.
Also at the Lecture Center will be a presentation on porcupines common to our Hudson Valley parks. “Porcupines in Our Presence” will be offered by Melissa Gillmer, head zookeeper at the Trailside Museum and Zoo at Bear Mountain Park on Thursday, February 16 at 7 p.m.
The SUNY Lecture Center is located between the library and the humanities building on the west side of the campus. No parking permit is required after 6:30 p.m. For directions or access to the interactive campus map (advised), visit www.NewPaltz.edu.
The final talk in the series will move the event to the SUNY Ulster campus in Stone Ridge on Thursday, February 23 from 7-8:30 p.m. at the College Lounge, Vanderlyn Hall, room 203. “Fire on the Ridge” will be a discussion of wildfires in the Gunks and the Biodiversity Partnership’s ongoing campaign to prevent them using managed burns. The talk will be led by Gabe Chapin, forest ecologist with the Nature Conservancy, and Hank Alicandri, director of Sam’s Point in Minnewaska State Park Preserve.
For more information about the lecture series and notice of any weather-related cancellations, visit www.MohonkPreserve.org.