Fractures near head of landslide (vertical)

mass wasting, gravity, erosion, crack, headwall

Antecedent River, Montana

Antecedent River


Talus on Mountain Slope

Talus on Mountain Slope

alpine, scree,



differential erosion, ridges, Block Mountain, BMMT

Soil Profile in grassland

Soil Profile

chemical weathering, pedogenesis

Mudcracks and Ripple Marks

Mudcracks and ripplemarks.

Mudcracks (left) and ripple marks (right) in rock of the Belt Supergroup. The mudcrack is about 20cm across; the ripple marks are roughly 1m across. (Image ID# belt-sedsrs-pic)

Marine Transgression diagram

Marine transgression

If you look at Time 1, you can see a coastline in cross-section, with sand being deposited closest to shore, mud a little farther out, and eventually carbonate material even farther out. As sea levels rise in Time 2, the sites of deposition for these materials migrates landward, putting mud deposition on top the earlier sand deposition and so on. In time 3, the sequence moves even farther landward, resulting in carbonate over mud over sand. If these materials become preserved and turned into rock, they form the sequence sandstone overlain by shale overlain by limestone – just what we see on top the Great Unconformity. (Image ID# transgression)