@odd Weathered granite. Not submerged in water, but subject to ice and snow every winter. Ice expanding in cracks makes the rock break in roughly cubic shapes, which then smooth around the edges. Contrast with past images of the "shark's teeth" on Wheeler Ridge. If there is uniform support from below, you get cubes; if there is a dropoff on one side, shear forces create triangles. (Source: Geologist Allen Glazner)
@Mandalorian I didn't until now.