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  • Writer's pictureMackenzie White

Climbing Rocks: How Geology Guides a Sport

Updated: Jan 27, 2023

On a cool May morning in 2018, John Flynn takes exit 23 off Interstate 93, heading west for a few more miles into the town of Rumney, New Hampshire. He passes through the few yellow blinking stop lights, continuing beyond the boundary of the town without pause as is common of Rumney visitors. Like the car behind him, he will continue until he reaches his reason for the dawn drive: Rumney Rocks.

While Rumney is a small, quintessential New England village, its resident population not exceeding a couple thousand, it is known across the world as a premier sport climbing destination. Scaling the rocks at Rumney has become a right of passage for people like Flynn, who has come to experience the diversity of different routes offered by the shape of the rock. The cluster of cliffs that make up Rumney are primarily schist, a metamorphic rock composed of minerals large enough to see with the naked eye. The rocks look as if you could peel them across thin, vaguely shimmering sheeted flakes, their grains visibly aligned.

Metamorphic rocks like those found at Rumney present a complex geologic story, their exposures often exhibiting complex folding, mineral assemblages, and layering. Though beginning as a sedimentary or igneous rock, their journey through geologic processes and time makes them unrecognizable from their original composition.  Forged by high pressures and temperatures deep below the Earth’s surface, schist forms from an original parent rock of dull, grey mudstone. 

The unique climbing at Rumney is the result of 400 million years of this deformation, its story beginning with the closure of an ancient ocean upon the intersection of the American and African continents. This collision buried the marine sediments, metamorphosing them through time in a geologic pressure cooker until finally thrusting them to the surface during the Appalachian mountain-building event. Rock climbers like Flynn now add to this ancient story of change, inserting bolts into the rock as they scale its irregular surface.

Many of these permanent bolts outline now famous routes, their metal rings intermingling with the dark, irregularly waving rock. Each crag – or small climbing area – is distinctive in its challenges and level of difficulty. Erosion has encouraged the diversity of the rock surface, forming overhanging roofs, long smooth slabs, slim cracks, and most notably for Rumney, scenic aretes offering exposure and views. While the climbers drill into the rock, stamp their fingerprints across the cliffs, and scrape crystalline grains from the surface, there exists an ever-present underlying respect among climbers for the rules dictated by the geology. The preexisting features in the rocks place boundaries on climbable routes, forcing directions where ascent is, and is not, possible. And so it is the climbers who must adapt to the rock, its varying crevices, its individual grooves molded through geologic time. 

Flynn advances up the cliffs at Rumney.

The schist at Rumney makes Flynn’s long drive and early wake up worthwhile. Metamorphic rocks like these are unique in their strength, containing hard minerals like quartz which are sturdily bound together, forming the solid sea of rock. Athletes prepare and act according to the specific rock type they are climbing, adjusting their methods appropriately and maintaining awareness of the rock’s individual features. Even those with no scientific backgrounds become self-made geologists, keeping in mind that an understanding of rock type is essential to a successful climb.

While some climbers like Flynn seek out the strong, smooth rocks like those found at Rumney, others have a different style, preferring the softer characteristics of sandstone or the expansive cliffs of limestone. The diversity of rock across Earth’s surface has spurred the creation of new types of climbing, approaches and gear catering to the geology. 

Crack climbing, for example, is typical on sandstone, a sedimentary rock formed by the compression of its various grainy layers. The surface of sandstone tends to reflect erosion’s constant defacing, with cracks sprawling in all directions. The size of these splits in the rock vary, some just large enough for a fingertip, others wide enough to fit a person. Climbers force their fists into these cracks, jamming their hand into the rock to secure their hold. 

While also a sedimentary rock, limestone warrants a departure from sandstone’s crack climbing approach. Limestone forms from the skeletal remains of marine critters, its exposures slowly dissolving in response to the acidity of rainwater. This form of erosion creates pockets in the rock, serving as often sharp but effective holds for climbers. A practice deemed “sport climbing” dominates limestone climbs, relying on fixed anchors and outlined paths up the rock. The soft whites and greys of limestone exist in stark contrast to the dark shades found at Rumney, serving as a reminder of their vastly different composition and formation history.

Flynn climbs limestone in Austin, TX.

As the morning climbers approach the walls of the Rumney cliffs, the sun begins to warm the east side of the rocks, causing a faint shimmer along the surface. The internal, elongated atomic structure of the minerals causes this glittering of light across the grains as Flynn and surrounding climbers unload their ropes, harnesses, and carabiners. While the brisk morning air is filled with lighthearted conversation and excitement for the climbing day ahead, a sense of reverence and focus remains present throughout all preparation. Necks are usually craned up, trying to “read” the routes, judging the grade.

The morning preparation at Rumney is a familiar practice for Flynn, who has climbed difficult routes along diverse geologic formations across the world. When he arrives at a new site, Flynn observes the rocks which formed over the course of deep time, a scale of history in which continents are born and destroyed, mountain ranges risen and buried, oceans expanded and erased in the relative geologic blink of an eye. 

The realities of rock climbing present many unavoidable perils. While some risk stems from human error, the geology of the region more often controls the fate of a dangerous climb. The same parallel minerals that give schist its glimmering aesthetic appeal also create zones of weakness where the rock is prone to split. Erosion that forms cracks and crevices that make ascent possible can lead to unexpected rockfall. Faulting along lines climbers use to grip can cause large areas of instability.

Beginning his climb up Rumney, Flynn enters into an intricate relationship with the geology. His mark on the rock builds on that of the climbers, erosion, and geologic processes before him. He wills himself up a cliff that has undergone profound physical and chemical changes through its 400 million year lifetime, taking occasional moments to appreciate the small variations in the rock making each climb unique. In the gym, each hold was made by a human with the geometries of human hands and feet in mind. But outside in the crag, each hold, or deep jug providing a brief rest, seems like a gift from the rock itself. 

Rumney has inherited fragmented pieces of the past, its rocks the result of dynamic changes and assembly across timelines far beyond those of human life.  As a day of climbing comes to a close and the rocks display a metallic sheen in the late setting sun, Flynn pulls his camera from his pocket to snap a photo of the cliffs against the pinkening evening sky. In this image are the rocks which were once each a moving thing, brought to the surface through violent uplift processes that left them here frozen, if only for a brief moment of geologic time.

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