Fig. 9.7 Pictures (©J.-C. Thouret and D. Miallier) showing relevant
landforms, deposits and mass movements around the maar lake and in
the Gelat Valley. ( a ) Cliff of trachybasalt lava fl ow below the Montchal
scoria cone on the SSE edge of the maar. ( b ) Note fractures and topple
across the 12 m-thick, trachybasaltic Montchal lava fl ow scarp. ( c )
Scar of slip, spring and runoff on weathered, Sancy pumice-rich pyro-
clastic deposits overlain by the Montchal lava fl ow. ( d ) Fractured cliff
of Mt. Sancy tephrite lava fl ow, NNE slope of the maar. ( e ) Fallen
blocks retained by young trees below the previous cliff are not cov-
ered by moss or lichen. ( f ) Open fracture in the Montchal trachybasalt
lava fl ow, SW slope of the maar. ( g ) Chaos of outsized boulders below
an eroded cliff of Montchal lava fl ow at the foot of the NW rim cliff.