Breccia pipes

Breccia pipes forming within existing fractures along the western shore of Yellowstone Lake, Wyoming.

Material filling the dissolved voids includes clasts of wall rock as well as beach sediments being washed into the voids. The lower structure on the left is about 0.7 m (2 ft) wide and 1.5 m (5 ft) high. Note the fracture alignment above the void structure on the right.