Potholes at Sculptured Rocks Road, Groton, New Hampshire, USA

Shaocheng Ji

Polytechnique Montreal

Yesterday I visited the potholes on hard bedrock consisting of mega-crystals of feldspar porphyroclastic gneisses along the Cockermouth River in Groton, New Hampshire, USA.

Address: 251 Sculptured Rocks Road, Groton, NH 03241

The stream has been carved by rapidly flowing water during years and years and eventually becomes a narrow canyon. These sculpted forms are among the natural wonders of the America East and present us an important tourist attraction for geological heritage. The potholes display consistently an increase in depth with increasing diameter. Rocky grinders were used to deepen and enlarge the potholes or form a stable, powerful vortex. The floor abrasion by coarse grinders is much more efficient than the wall erosion by polishing of suspended sand. The potholes from the Sculptured Rocks Road in Groton were misinterpreted as a result of glacial holes formed during the ice age time.