Tag Archives: geology

The Ellenville Fault Ice Caves – A National Natural Landmark

The most popular features of the Sam’s Point Area of Minnewaska State Park Preserve are the Ellenville Fault Ice Caves. This remarkable system of crevice caves fills up with ice and snow each winter, and retains some of its ice well into the summer. Even when the ice is completely gone, the caves remain cool all year round. This unusual phenomenon has drawn people to the caves for generations.

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A postcard from c. 1909 showing the snowed-over entrance to one of the caves. The man in the image is an illustration, and slightly exaggerates the scale.

The significance of the caves has even been recognized by the National Park Service. In 1967, the NPS designated the Ellenville Fault Ice Caves as a National Natural Landmark. This designation is given to natural sites that exemplify the special or unique biological or geological features of a region.

Geologically, the Ice Caves are unlike other caves in the Northeast. Most cave systems are made of limestone, which is easily eroded and dissolved by water. This results in the large, open caverns that most people imagine when they think of caves. The Ellenville Ice Caves, on the other hand, are formed out of extremely hard and insoluble quartz conglomerate. When underlying rock layers were folded by tectonic movement, the hard conglomerate separated along existing joints in the rock.

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Cutaway images demonstrating two forms of crevice cave formation. Source: Jack Fagan, Scenes and Walks in the Northern Shawangunks

The caves remain cold because of the natural refrigeration system that exists within them. When air moves across the top of the crevices, the colder, heavier air sinks down into them. The cold air then becomes trapped in the caves, keeping them at a comfortable temperature even during the hottest days of the summer.

While they received the National Natural Landmark designation because of their unique geologic importance, the Ice Caves have a great deal of ecological impact as well. The NY Natural Heritage Program recognizes the ice cave talus community as globally uncommon and rare in the state and a priority for protection. Because of their cold microclimate, the Ice Caves are home to several species that are infrequent in the region. These include goldthread (Coptis trifolium), mountain ash (Sorbus americana), and black spruce (Picea mariana), among others. Scientists have also taken interest in the presence of a species of cave-dwelling crustacean (Stygobromus allegheniensis) that is only found in four states: New York, Pennsylvania, Maryland, and West Virginia. This little arthropod lacks eyes, as it does not need them in complete darkness. It is also able to survive being frozen, a necessary attribute for surviving winter conditions in the caves.

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Strygobromus allegheniensis. Note the pale coloration and lack of eyes, typical features of cave-bound organisms. Image source: Espinansa et al. (2015)

The Ice Caves have local cultural significance as well. Many residents of the Shawangunks remember the days of “Ice Caves Mountain,” when the Sam’s Point area was managed very differently than it is today. From the late 1960s to the early 1990s, much of Sam’s Point was privately owned and operated as a tourist attraction. Visitors could drive their cars right up to Ice Caves, while a pre-recorded cassette tape described the various features encountered along the way. Doors were placed over the caves to keep the ice inside year-round, and the ice was lit up by multicolored flood lights. A rock wall was built on the cliffs of Sam’s Point to dissuade visitors from getting too close to the edge. While it may have been somewhat kitschy by today’s standards, it cannot be denied that “Ice Caves Mountain” was an important step in allowing the greater public to experience this previously obscure natural wonder.

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Gully with snow at Sam’s Point, photo by Greg Edinger, image courtesy of the New York Natural Heritage Program

Many things have changed since the Ice Caves Mountain days. While Sam’s Point is still managed for recreation, there has also been a large shift in focus towards conservation. Visitors may no longer drive through the park, and the cave doors have been removed in favor of letting the natural ice cycle of the caves take place. Interpretive displays within the park focus on the natural history of the caves, rather than just their physical spectacle.

While National Natural Landmark status highlights the importance of a site, it is up to the owners of that landmark to manage and protect it. Fortunately, Sam’s Point is part of a Park Preserve, meaning that all of the plant and animal life within it is protected. As such, those who appreciate the cultural, geological, and ecological significance of the Ellenville Fault Ice Caves are able to experience them to the fullest extent.

Tim Howard, NYNHP
Ice and trees in leaf – a late spring exploration of the ice caves. Tim Howard, NYNHP

Want to explore the Ice Caves? State Parks staff offer guided hikes to both Shingle Gully and the Sam’s Point Ice Caves; click here for the Sam’s Point Area calendar of events.

References:

Fagan, Jack (2006).  Scenes and Walks in the Northern Shawangunks (3rd Ed.). Mahwah, NJ: The New York-New Jersey Trail Conference.

Espinasa, L., McCahill, A., Kavanagh, A., Espinasa J., Scott, A., Cahill, A. (2015).  A troglobitic amphipod in the Ice Caves of the Shawangunk Ridge: Behavior and resistance to freezing.

NatureServe Explorer Allegheny Cave Amphipod

Ice Caves Talus Community Conservation Guide

Featured image courtesy of Mike Adamovic, from Ice Caves of the Shawangunk Ridge

Post by David Hendler, SCA Education and Stewardship Intern

 

 

 

Niagara Rocks!

photo by Michael Drahms

Extending over 7 miles from Lewiston, NY to Niagara Falls, NY, the Niagara Gorge offers many recreational opportunities to explore nature. You can experience the gorge at Earl W. Brydges  Artpark State Park, Devil’s Hole State Park, Whirlpool State Park, and Niagara Falls State Park. While there, stop to see the amazing rocks that make Niagara the wonder that it is today!

Visible downstream at the lowest level of the gorge, is the oldest visible rock layer within the gorge wall. This layer was deposited along a coastal area of a warm shallow sea in the late Ordovician Period, alternating between below and above sea level. The periodic exposure of the iron rich sediments resulted in the coloration visible in the sedimentary rock of the Queenston Shale. As you travel upstream the tilt of this layer causes it to disappear below visible levels.

Niagara Escarpment

The rocks seen in the walls of the Niagara Gorge are sedimentary; they are made from sediments deposited in a shallow sea that covered much of the eastern U.S. and adjacent Canada around 440 to 410 million years ago (middle part of the Silurian Period). Rocks, such as limestone, shale, sandstone and dolostone, are seen as distinct layers. Some of these layers, for instance the soft, easily eroded Rochester Shale below the caprock of Niagara Falls, contain a great diversity of marine fossils, such as brachiopods, trilobites, corals and crinoids.

These rocks are layered, from oldest at the bottom to youngest at the top along a long ridge known as the Niagara Escarpment. The Niagara Escarpment is a prominent cliff-forming cuesta that extends from western New York into southern Ontario, northward to the upper peninsula of Michigan, and then bends downward into eastern Wisconsin and Illinois. The escarpment is capped by relatively hard, resistant rocks of the Silurian-age Lockport Group (chiefly dolostones and limestones), which are underlain by less resistant rocks (shales and sandstones, such as the Rochester Shale).

Layered Rocks

Near the end of the last ice age, around 12,300 years ago, the Niagara River began to flow over the Niagara Escarpment, located at what is now Lewiston, New York. Through the process of erosion the falls have receded to their present location.  In the past, the falls receded on average 3-6 feet per year. However, the rate has been greatly reduced due to flow control and diversion for hydropower generation, to a mere 3-6 inches per year. 50,000 years from now, at the present rate of erosion, the remaining 20 miles south to Lake Erie will have been undermined. There won’t be a falls anymore, but rather a series of steep rapids!

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While visiting Niagara Falls, or hiking in the Niagara Gorge, take some time to marvel in the events and processes that took place over time. From continental collisions to ice-age glaciers and the present day Great Lakes drainage basin, we are fortunate enough to witness the interactions of nature.

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Links to additional information about the formation and geology of the Niagara gorge and the Niagara Falls geological area.

Post and Niagara Gorge photos by Mike Drahm, State Parks, Niagara Region

Geology Exposed at Chimney Bluffs State Park

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Chimney Bluffs looking east from the shoreline. Photo by Brett Smith.

Some people are drawn to water and some are drawn to dramatic landscapes, Chimney Bluffs State Park on the shore of Lake Ontario has both. Located in Wolcott, New York the park’s namesake bluffs stretch for ½ a mile revealing its ever-changing ancient past.

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Chimney Bluffs looking east. Photo by Brett Smith.

During the last ice age from 2 million years ago until about 10,000 years ago there were a series of glacial advances and retreats that formed the Great Lakes that changed the landscape of the north-central part of the United States in many ways.  One of the clues that glaciers leave behind are called drumlins. We see drumlins as elliptical hills. These hills are blunt on the upglacier end and taper into and elongated tail on the downglacier end, similar in shape to a teardrop. Drumlins form parallel the direction the movement of the ice.  These hills usually form in clusters; the exposed upglacier end of the drumlin at Chimney Bluffs State Park is one of roughly 10,000 drumlins located south and east of Lake Ontario.

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Click on map to enlarge.

The term drumlin refers to the hill’s shape, not its composition. Some drumlins are solid rock and some are composed of glacial till. Till is a mixture of different sized rock fragments and sediment deposited as glacial ice melts. The drumlin at Chimney Bluffs State Park formed when one glacier melted and deposited the till, later a south moving glacier reshaped the material into its present shape.

The north end of the drumlins has been eroded by thousands of year of wave action, wind, rain and snow. As the north end erodes the exposed material is carved into magnificent and ever changing formations. The bluffs are constantly changing source of beauty and danger.

Post by Josh Teeter, OPRHP.