Geoscience Reference
In-Depth Information
Fig. 7.12
Left: surface of karst sharpened by rain on hard calcareous rock (Flaine, France;
2200 m); the scale is given by the coin. Right: in the same zone (2000 m), rounded karst
differentiated within the soil, after exhumation (scale is given by the ice axe).
Photos
: author.
The dissolution of bare limestone slabs on the Massif de Platé (Station
de Flaine, Haute-Savoie, France) has been calculated from the water
surplus (annual rainfall minus actual evapotranspiration), taking the
temperature into account (Table 7.4). This rate is expressed in m
3
km
-2
y
-1
. But the same figures are also applicable to the number of cm of
ablation for 10,000 years, which can be more easily understood.
Estimation of rates of dissolution
Table 7.4
Dissolution in the Massif de Platé (Flaine, France) according to
Maire (1990).
P, mm y
-1
AET, mm y
-1
P-AET,
Altitude, m
T, °C
Dissolution,
mm y
-1
m
3
km
-2
y
-1
1500
3.16
2190
359
1831
14.82
2000
0.04
2590
281
2309
16.56
3000
-6.21
3390
143
3247
17.30
Geomorphologists have devised methods for comparing and
validating these determinations (Fig. 7.13).
Base of
erratic
Erratic
Limestone bed
a
Original surface
of bed
x
y
Limestone bed
b
Fig. 7.13
Estimation of the rate of dissolution of a limestone slab in the mountains
(Maire 1990).
Glaciers, because of their abrading power, leave behind clean and
smooth limestone domes. The limestone beds that can presently be
