A crack is an absence — a black void framed by rock. In purely geological terms, a crack can result from stress or differential erosion; it might be a joint or a fault (see “Cracks 101,” by crackmaster and research associate Alan Lester). But in climbing terms, a crack is something different.

In North America, crack climbing means selfsufficiency: gauging size, assessing your rack, and slamming in gear as needed. (Sure, the Euros sink “spits” next to splitters, but we don’t need to talk about that here.) It also means favoring technique over power, or rather, learning to harness your inner brute to cup and jam, ring-lock and foot torque, armbar, chimney, and chickenwing — because go-for-broke laybacking and praying for face holds often aren’t “technique” enough. Andrew Burr, based in Salt Lake City, knows the American West like few photographers; he’s always on the road, climbing and shooting. Over the last five years, Burr has amassed hundreds of images of the best fissures in the region, at all shapes and sizes. It was tough for us, selecting the following 13 images from the many, but with Burr’s help, we finalized this sequence showing cracks from smallest to largest — from the incipient seam to the monster bomb-bay. Dig in, tape up, and climb on.

Jason McNabb, Lieback from Hell (5.12c), Black Hills, South Dakota

For those new to crack climbing . . . well, it can be scary. And nothing is scarier than the incipient seam, a crack so tight even Sonnie Trotter couldn’t funk in micro pro. The history of the Lieback, bolted at Raspberry Rocks by Brent Kertzman roughly a decade ago, is, like most routes in the Hills, vague — it’s unclear if it’s seen a true FA. And the Lieback isn’t so much a crack as an eroded dike — the seam was once filled with calcite that’s since dissolved to leave a shallow, boxed-in micro fissure. In 2007, the FA seemed in the bag, as Jason McNabb (left) almost hiked . . . hiked, that is, until a dinner-plate-shaped foothold broke and buzz-sawed toward the ground, nearly decapitating the belayer and resulting in a head wound that took 15 staples to close.