Skip to main content
U.S. flag

An official website of the United States government

Junction Butte basalt displays columnar jointing Overhanging Cliff

Detailed Description

Outcrop of the Junction Butte basalt alongside the road at Overhanging Cliff. The zone of prominent columnar jointing at the base of this thick lava flow formed by contraction cooling; it overlies stream-deposited sediments and is overlain by a zone of irregularly intersecting joints.


Public Domain.