'
192
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962
Fig. 3. The Nari detachment line
The process of Nari disintegration starts at the base of the mountain slopes
near the main tributary (fig. la), being initiated by undercutting of this slope
base by the floodwaters of the main tributary. As a consequence the Nari is
eroded, and the soft chalk revealed. Later on, blocks of Nari are detached from
the slope above and creep slowly downslope. A low cliff (about 2-3 m) is
found on the line of the Nari detachment (fig. 3) for which the name Nari line,
or Nari detachment line, is suggested by the author. The process continues
slowly upslope (fig. lb) until the soft rock, and the calcareous soil associated
with it, are exposed along the entire slope.
The disintegration process is accelerated by the aid of small tributary gullies
which cut upwards into the soft rock from the main tributary. As a result small
depressions are formed (fig. lc, d, fig. 2a) which are bordered on three sides by
the Nari line. As the process continues, these depressions widen and occasionally
merge, leaving islands of Nari at the lower part of the slope (fig. 2b). Ultimately
all the Nari disappears, but this final stage has been reached in a few places only.
The Nari disintegration is much faster on the southern slopes than on the
northern ones. It seems that the dense vegetation on the northern slopes
retards disintegration by decreasing erosion [cf. figs. 4 and 5).
The features of the Nari slope are quite different from those of the chalky
slope. Most, or even all of the Nari slope is convex; if present at all, the con
cave part is restricted to the slope base. This slope generally lacks scree and
only occasionally on the steepest slopes may there be found insignificant
amounts of scree. On the other hand, the slope where the Nari has been
