Welcome to my Earthcache! An Earthcache is a special type of geocache where there is no container to find - instead you are looking for a unique geological feature of the area and need to answer questions, as well as posting a picture, in order to claim the find. This EarthCache takes you to the Quartz Conglomerate boulders in Rock City Park, Olean NY. These unique rocks are part of a process from millions and millions of years ago, and they have been shaped by a variety of processes into what you see today. This particular earthcache looks to explore the overhangs above you (look up... WAY up!) and how they use gravity and other forces to remain in flace for millions of years.
Please Note: Rock City Park is a private attraction that is open from May to October annually from 9am until 5pm. The park may close early in case of inclement weather or private events within the park. There is a fee of $8.00 per adult/$5.00 per child to enter the park. This Earthcache has been placed with the permission of park manager Nate Smith. A big thanks to bigguy14760 for obtaining permission from Nate and assisting with the creation of this earthcache.
EARTHCACHE REQUIREMENTS
As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. Please include a list of all cachers with your answer, if answering for more than one caching name. There is no need to send individual answers.
To claim a 'find' for this Earthcache you must answer the following questions and send your answers in a message or email to the owner using the link at the top of the page. You can log your find with a photo at GZ. Send your answers to the tasks. I will be in contact if there is a problem, no need to wait for a response as long as the required photo is included in your log.
Observational Task
At GZ, you should be standing at the bottom of Rock City Park, staring up at a very large overhang that makes it seem like you are in a cave. You can access this area by one of two ways - a steep metal staircase from the top, or by taking the trail "backwards" down the Devil's Staircase. In either case, this area is not recommended for those who are mobility challenged.
Questions to Answer:
1. Describe the Overhang: Observe the rock overhang. Estimate the length of the projection (in feet or meters). What kind of rock makes up the overhang? Describe its texture, color, and layering.
2. Explain the Formation: Based on your observations and this lesson, explain how this overhang likely formed. What evidence of erosion, weathering, or collapsing do you see?
3. Gravity at Work: Why do you think this overhang has not collapsed? Consider the visible structure, support, and size.
4. Photo: Include a photograph of yourself, your GPS, a signature item, thumbs up, etc at your favourite formation within rock city park. You do not need to show your face in the photo, but your photo must be unique to you. In the event of group photos, please have each member of your group upload the photo (each log should have at least one photo uploaded).
EarthCache Description
At Rock City Park, you're standing on the remnants of a powerful prehistoric river system. These rivers carried quartz-rich sediments that eventually formed the quartz conglomerate, a rock type known for its striking pebbled texture. This EarthCache explores the full lifecycle of this rock—from mineral formation to sediment deposition and final lithification—while helping you identify the rock’s components in the field.
What Is an Overhang?
An overhang is a rock formation where a mass of rock projects outward beyond its base. These natural structures appear to defy gravity, as they remain suspended above the ground without collapsing under their own weight.
How Are Overhangs Formed?
Overhangs form over thousands to millions of years due to differential weathering and erosion—processes where rock layers of varying hardness erode at different rates:
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Sedimentary Rock Layering:
Rock City Park sits atop Devonian-age quartz-rich sandstone, part of the Olean Conglomerate. These sedimentary layers often consist of alternating hard and soft materials.
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Erosion by Water and Ice:
Over time, freeze-thaw cycles, chemical weathering, and surface runoff exploit natural fractures in the rock. Softer rock beneath or beside harder layers is worn away faster.
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Gravity and Fracture Expansion:
As the weaker material erodes out from underneath, blocks of harder sandstone remain jutting outward, forming ledges and overhangs. Natural vertical joints allow sections of rock to break off cleanly, creating angular blocks with dramatic projections.
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Glacial Legacy:
During the last Ice Age, glaciers scoured and reshaped this region. When the ice retreated, it left behind massive slabs and blocks, many already pre-fractured. These boulders settled in positions that favored the development of exposed overhangs as erosion continued.
Why Don’t Overhangs Collapse Under Their Own Weight?
At first glance, it seems like overhangs should fall—after all, they project out into open space. But gravity doesn’t act in isolation; it's how the rock structure resists gravity that determines an overhang’s lifespan.
1. Compressive Strength of Rock:
Sandstone, like that found in Rock City Park, is a strong, compacted sedimentary rock with high compressive strength. This means it can bear a lot of weight pushing straight down on it, which is exactly what gravity does. As long as the stress remains within the rock’s strength limits, it won't collapse.
2. Stress Distribution:
If the rock’s mass is anchored deeply enough into the cliff or boulder behind it, gravity's force is transmitted back through the rock into the more stable base. Think of it like a bookshelf bracket: as long as enough of it is lodged in the wall, it can project outward safely.
3. Rock Cohesion and Jointing:
Rock units that lack major fractures or have bedding planes angled upward into the slope are better at resisting gravitational pull. At Rock City Park, the sandstone blocks often exhibit horizontal bedding and relatively clean breaks, which allow large portions to stay intact even when part of the mass is overhanging.
4. Counterbalancing and Mass Distribution:
Many overhangs are actually just parts of larger rock units with most of their mass still sitting back behind the visible edge. Gravity acts on the entire rock, not just the protruding portion. If the center of mass remains within the footprint of the supporting base, the overhang stays stable.
But Gravity Always Wins Eventually:
Over time, weathering weakens joints and increases internal stresses. Water enters cracks, freezes, and expands, or root systems grow into fractures. These forces add stress that gravity will eventually exploit, leading to rockfall or collapse. Some fallen blocks visible at Rock City Park are former overhangs that finally succumbed to this balance tipping.
Additional Information:
Rock City Park is home to one of the largest exposures of exposed rock formations in the eastern United States. The overhangs, crevices, and balancing rocks create a natural maze of stone that continues to evolve through geologic time.
References
This cache was placed by a PROUD Platinum Earthcache Master.
