Tag: rock

A streamlined, wind-carved ridge of rock or compacted sediment, aligned parallel to the prevailing wind direction. Yardangs form when wind-driven sand abrades softer material, sculpting it into elongated, aerodynamic shapes — narrow at the windward end, wider at the lee. Fields of yardangs can resemble fleets of stone ships sailing across the desert floor.

A natural depression in sandstone that collects and holds rainwater — similar to a tinaja but often larger and occurring on slickrock surfaces rather than in canyon bottoms. Waterpockets can be the size of bathtubs or swimming pools, and in the desert they are oases in stone. Capitol Reef National Park was originally called Wayne Wonderland but was renamed for the Waterpocket Fold — a massive geologic formation lined with thousands of these basins.

A stone that has been shaped, faceted, and polished by wind-driven sand — its surface planed smooth on the windward side, its edges sharpened to ridges. Ventifacts are the desert's whittled stones, each one a record of prevailing wind direction and duration. Small ventifacts can be picked up and examined; large ones are boulders sculpted in place over millennia.

A visible boundary on the wall of a glacier valley marking the maximum recent thickness of the ice — a horizontal line separating weathered rock above (which was exposed to the sky) from polished or unweathered rock below (which was covered by ice). The trimline is the glacier's high-water mark, etched into the valley wall. As glaciers thin and retreat, trimlines become increasingly visible — stark evidence of how much ice has been lost.

A natural rock basin — a pothole in bedrock, typically in a canyon or wash, that collects and holds rainwater. Tinajas can be inches deep or deep enough to swim in, and in the desert they are critical water sources for everything that lives. Some hold water year-round; others last only weeks after rain. Knowing where the tinajas are is desert literacy.

The unsorted mixture of clay, silt, sand, gravel, and boulders deposited directly by a glacier — dropped in place as the ice melts, without the sorting that water would provide. Till is the glacier's residue: everything it picked up, ground down, and carried along, dumped in a jumble when the ice retreated. The soil of much of the American Midwest is glacial till.

The general term for all solid material ejected into the air by a volcanic eruption — ash, pumice, cinders, bombs, and blocks, regardless of size, composition, or distance traveled. Tephra ranges from fine dust that circles the globe to car-sized boulders that land within a mile of the vent. It is the word that contains the entire spectrum of volcanic fallout.

 A field of broken rock that has fallen from the cliff above and accumulated at its base. Larger than scree — individual rocks range from grapefruit-sized to refrigerator-sized. Crossing a talus field is an exercise in choosing which rocks to trust.

The surface on which a track is printed — mud, sand, dust, snow, wet leaves, dry leaves, duff, gravel, bare mineral soil. Substrate determines everything about what a track looks like and how long it lasts. The same animal leaves a crisp, detailed print in wet silt and an unreadable scuff in dry pine needles. Learning to track is largely learning to read substrates — knowing what each surface can and cannot record.

A perfect, clean, parallel-sided crack in the rock face, often running for dozens or hundreds of feet without variation. The most prized feature in crack climbing — consistent, protectable, and deeply satisfying to climb. Splitters in sandstone or granite are what climbers travel across the world to find.