Travertine terracing: patterns and mechanisms - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 343

Fig. 5. Dots, Slopes and inter-dam distances (IDD) measured in minidams by Pentecost (2005). Line, Theoretical IDD
with constant terrace height h ¼ 4 mm, minimal IDD k ¼ 6 mm (see text).

resulting morphology was reminiscent of the scal-
loped microterracettes seen on steep travertine sur-
faces with thin film flow, where flow velocity is
fairly well predicted by slope alone. For a film thick-
ness h, gravity g, slope a, kinematic viscosity n and
an empirical constant K, we have
u ¼ 8gh 2 sin a
Kn

(Horton et al. 1934). However, in order to under-
stand the mechanism for the slope-precipitation
relationship, a more detailed model is required.
Hammer et al. (2007) used a computer simulation
of shallow water flow over a surface (computational
fluid dynamics), coupled with a simple precipitation
model where growth rate was proportional to flow
velocity. This produced a proximal mound and
distal apron covered with terracettes, coarsening

Fig. 6. Visible-light (a) and infrared (b) images of the same area in Mammoth Hot Springs, Yellowstone National
Park, USA. Hot water flow from left to right. Lower right area (bright, Fig. 6a) is dry. Plumes of hot water
(arrows, Fig. 6b) in the largest pool demonstrate localized flow over the upstream rim.