Control of Substrates on Pothole Geometry

In the present study, we recorded the depth (d), aperture radius (r), chamber radius (r_c) and size of the largest grinding tool (G) of 64 potholes from Subarnarekha river bed near Ghatsila, Jharkhand, India. Subsequent to the analysis, distinct control of substrates on pothole morphology became apparent. The average d/r ratio (γ ) 2.07, of potholes on quartzite was significantly different from that of potholes on mica-schist. Variations of major and minor aperture radii of micaschist (60.59%) were much higher than those on quartzite (18.66%). The d–r linear law, d = Nr + M (where M = critical size of seminal depression that grows into a mature pothole and N = ratio between the rate of deepening and widening) seemed to hold good for potholes in both the substrates. Thirty four potholes on quartzite exhibited M = 20 cm, N = 1.2 explaining the faster rate of deepening than widening. Thirty potholes on mica-schist exhibited M = 4.9 cm, N = 0.67 explaining the faster rate of widening. On quartzite, potholes with d/r >2 exhibited r_c > r which was absent in potholes on mica-schist. The d–G and r–G relations found in potholes on quartzite were insignificant for those on mica-schist.