Propped Natural Arch

(Genetic type)

Examples: Eagle Canyon Arch, Jug Handle Arch, unnamed arch, unnamed arch, unnamed arch

This type of natural arch is frequently called a "jug handle" and closely resembles the buttress natural arch. Like the buttress type it is always projecting. However, the opening is an upright slotted aperture and the lintel is vertical, at least nearly so. It can form when a vertical joint occurs near the end of a rock projection. This joint need not be exactly vertical, or even straight. Indeed, it is frequently slanted and curved with a slight bow in the direction of the projection. The joint usually coincides with the face of the cliff at the interface between the projection and the cliff.

Occasionally such a joint widens, usually due to freeze expansion and thermal exfoliation. The result is an upright slotted aperture with a long axis slightly bowed and off the vertical. Rather than the lintel supporting the weight of the wall at its end, however, just the opposite is happening. The lintel is vertical with most of its weight supported at the base. However, a component of the lintel's weight forces it against the cliff, keeping the joint closed above the aperture.

Compression strengthening does not play a significant role in the formation of this type of natural arch. Consequently, propped natural arches usually do not have long lives. Specifying a maturity attribute for this type of natural arch is seldom appropriate.