The weirdest terrain on Triton is the so-called cantaloupe terrain, characterized
by closed depressions 30 to 50 kilometers wide, separated by ridges. It has
now been shown that these depressions resemble those formed by diapirs, which
are blobs of material that rise from depth and penetrate through a surface layer.
This suggests that Triton's crust is layered. Some of the smooth deposits at
right may be volcanic in origin.
(NASA text and photo)