ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

ALEXANDRE M. KALININ
The types of slopes of the Lena River
Department of Geography, Moscow State University,
119899 Moscou, Russia
The following types of slopes can be found in the basins of
the Upper Lena, the Aldan, the Vitim, the Olekma rivers:
actively developing, episodically active and passively developing.
The following slopes can be included in the actively
developing group: rockfall, talus, rockfall-talus, structural,
kurumes slopes.
The following slopes can be included in the episodically
active group: rockfall-talus slopes leaning on the young river
plain. The rockfall-talus, talus and kurumes slopes
strengthened by the vegetation can be included in the passively
developing group. They can become active in the result
of fires and wash outs. The expansion of the kurumes
slopes is tightly related with the lithology of the layer.
Average speed of the kurumes movement is equal to 5-10
centimeters a year according to long-standing phototheodolite
data. The volume of the supplied material for one
meter of the river bank is equal to 0,1 cu.m, Kurume-rockfall-talus
slopes are steeper, have no vegetation. They supply
most of the material for the bed, having the annual volume
of 1,5-2 times more than the kurume slope.
The slope morphology can be determined by the intensity
of the wash out of its base by the river. Large fragments
get stuck in the river bed and, thus, form a «skeletone» base
for a new level of the river plain. Thus, the forming of
the river flat regulates the development of the river slopes.
One can found some episodically active slopes, the activation
of the movement of which is determined by the erosion
activity of the river. In the basins of the Lena and Aldan
rivers one can easily find the rockfall and talus slopes
(like «Lenin's Columns» and «Palaces»),
The displacement of the detrital rocks is limited by the
wood and bush vegetation of the rear stitch of the bushrocks.
The detrital rocks, being beyond this natural obstacle
are getting their volume up to their critical volume, and
after an overflow, the detrital material, cutting down the
trees, rushes down the river bed.
When taluses reaches the angle of natural slope that will
lead to the over growing with the beach-rocks. The talus,
kurume slopes are base on the 1-11 levels of the over
flood-plain terraces. Thus, one can say, that (perestroyka)
reconstruction of the slopes.takes a long time, having in
mind the changing basis of the denudation.
D.E. KAPULE
Geomorphological hazards: a case study
of the Nakuru Area, Central Rift Valley, Kenya
Department of Geography,
University of Nairobi, p.o. box 30197, Nairobi, Kenya
The paper presents the causes and the effects of geomorphological
hazards in the Nakuru area, Central part of
the Rift Valley, Kenya. The study shows that the hazards
are mainly caused by ground subsidence manifested on the
surface by several linear depressions which are opened during
heavy rainfall due to the collapse of loose unconsolidated
deposits. The depressions are controlled by faults
and fractures of tectonic origin currently forming part of
the underground drainage systems developed during the
last few years when the faults, controlling the fissures, were
reactivated by erosion. The effect of these factors call for
sensible planning so as to limit the extent of loss of property
and life.
Geomorphological mapping using aerial photographs, satellite
images and ground survey can greatly assist in monitoring
the development of features which are the indicators
of hazards in the area. Local knowledge from the people
affected by hazards is of great importance in assessing
geomorphological processes responsible for these hazards.
DAVID KARATSON
Two fundamental types of erosion calderas
Eotvos University, Department of Physical Geography
1083 Budapest, Ludovika ter 2, Hungary
Two major types of erosion craters/calderas, characterized
usually by a single or by several outlet valleys, respectively,
can be distinguished by channel network development.
The first is typical of temperate climates with no more than
1000-1500 mm/year annual precipitaion, and is characterized
by a valley development which is directed by the breached
crater/caldera interior as a drainage basin. The second
seems to beformed above a climatic threshold (ca.
1500-2000 mm) where amphitheatre valleys can evolve.
These are high-energy valleys, of which a number can
penetrate into a closed crater/caldera, degrading it more
intensely.
Erosionally transformed craters can be referred to as erosion
craters, erosionally transformed calderas to as erosion
calderas - the boundary seems tobe at around 3 km in diameter.
Active craters and calderas are usually distinguished
by a diameter of 1 km; by using the greater value, the definition
can be extended also to inactive volcanoes.
Since temperate climates are characteristic of continents,
craters/calderas of all volcano types (pyroclastic cones,
stratocones, basalt domes, caldera volcanoes) can be transformed
by the erosion process determined by drainage
basin. On the contrary, development of amphitheatre valleys
is confined largely to oceanic islands which are typically
basaltic, so the second major crater/caldera type is connected
primarily to basaltic volcanoes.
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