chimney

As used to denote landforms, the term chimney most commonly refers to slender rock towers that resemble their man-made brick-and-mortar counterparts when considered from afar. But the word is also applied to aspects of the landscape that resemble masonry flues when viewed from within—that is, parallel-sided slots or grooves, approximately two to twenty feet across, that cleave steep precipices. For instance, North Chimney, Fields Chimney, and Alexanders Chimney, all of which are located on the lower east face of Longs Peak in Colorado. Historically, mountaineers have relied on such chimneys to provide routes of ascent up otherwise impassable rock faces. Sometimes a chimney will split the underside of an overhang, in which case it is called a bomb-bay chimney.

Jon Krakauer