Geoscience Reference
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Table 2.2 Lithological composition and landslide potentiality index value (LPIV)
Lithological
composition
Number
of cells
(F
1
)
(0.25
km
2
)
Number
of cells
(%)
Number of
landslide
occurrence
cells (F
2
)
Number of
landslide
occurrences
cell (%)
Landslide
occurrence
ratio
Landslide
potential
index
(LPI) = F
2
/
F
1
×
100
Gneiss, mica-
schist and granu-
litic rocks (A)
26
18.57
19
22.09
0.73
73.07
Calc-granulie,
marble, quartz-
granulite and mica
schist (B)
16
11.42
9
10.47
0.56
56.25
Mylonitised gran-
ite with sub-paral-
lel thrust (C)
13
9.28
8
9.30
0.61
61.54
Phyllite, silvery-
mica-chlorite-
schist, grey seri-
cite (D)
13
9.28
9
10.47
0.69
69.23
Slate phyllite with
quartzite, quartz-
schist and grey-
wake schist (E)
29
20.71
19
22.09
0.65
65.52
Sandstone, quartz-
ites, shales, thin
seams of crushed
coal (F)
16
11.42
7
8.14
0.43
43.75
Soft sandstone,
mudstone, shales,
conglomerate and
marly shales and
lignite (G)
27
19.29
15
17.44
0.55
55.56
Seepage through heavily disintegrated and decomposed materials and formation
of clay minerals, which induces slope instability.
Rocks are traversed by quartz and quartzo-felspathic veins and the rocks are
often highly metamorphosed and jointed.
Recrystallisation and cataclastic deformation have destroyed the clastic texture
with intense granulation along narrow zones of fracture.
The apexes of the sliding zones are predominated with good amount of organic
matter which encourages high water holding capacity and volume expansion.
The apexes of the sliding zones are deforested and are susceptible to both sheet
and gully erosion.
Both Damuda and Swialik provide intensively deformed sandstone which
destroys the clastic texture and promotes slope instability.
Krishnaswamy (
1982
), Lahiri and Gangopadhyay (
1974
) studied structure and
stratigraphic pattern of rocks and their relation to landslide phenomena with par-
ticular reference to Himalayan region. Nautiyal (
1951
,
1966
) presented some
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