ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Sur le plan volcanologique, le mont Manengouba est un
volcan polyphase qui a connu entre le Tertiaire et l'Actuel
trois types d' eruptions volcaniques: a) les eruptions calmes
et fluides, b) les eruptions calmes et visqueuses, c) les
eruptions explosives et fortes.
Nous avons fait ume cartographie de ce massif en integrant
les zones a risques pour des eruptions futures. Ces zones
sont principalement le nord-est du Manengouba du fait
des pentes regionales favorables a une grande et rapide
progression des coulees, ainsi qu'une forte concentration
des cones d' explosion; le sud-ouest du massif acause de la
proximite du graben de Tombel et enfin la caldeira d'Eboga
du fait de la presence de deux volcaniques susceptible
d' emanation gazeuse.
VINCENT KAKEMBO
The implications of land use change and geology on gully
initiation in the Eastern Cape, South Africa
Department of Geography, University of Fort Hare,
Private Bag X1314, 5700 Alice, South Africa
The origins and development of gullies in a sub-catchment
of the Great Fish and Keiskamma rivers, South Africa, are
traced by analysis of sequential vertical aerial photographs
and orthophoto maps from 1938 to 1992. Gully location in
relation to slope position and the catchment's micro-geology
is investigated using Pc Arc/Info Gis. Widespread
gully initiation and intensification appears predominantly
from the mid 1970's, coinciding with a period of extreme
rainfall and flood events in the region. Conversely, gullying
at four specific sites, identified as abandoned cultivation
fields, is discerned to commence during the early 1950's
followed by rapid incision in the mid 1970's. At the sites, a
Dolerite Sill through the region, which marks a sharp
break in slope, forms a zone of gully initiation. The Dolerite
Sill is also identified during longitudinal and cross profile
surveys as the limit to headward gully extension and
boundary of thick unconsolidated colluvium accumulation.
The implications of this relationship to erosion remedial
measures and land management strategies are crucial.
TOMASZ KALICKI
Holocene development of the middle Vistula flood plain
in the gap section (Poland)
Department of Geomorphology and Hydrology, Institute of Geography
and Spatial Organization, Polish Academy of Sciences,
ul. sw. Jana 22,31-018 Krakow, Poland
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The study area is situated in the gap section of the Vistula
valley between Kielse-Sandomierz and Lublin Upland in
the middle Poland. In the narrow reache there are segments
of the flood plain of various age. Here the paleomeanders
are preserved only sporadically. A small width of
the valley restrained free meandering so the river had likely
a permanent tendency to anastomosing as well as to hindered
preservation of the older series of channel alluvia.
However records of changes in the type and rate of sedimentation
on the flood plain are found in few preserved
older fragments. The evidence of changes is provided by
subsequent covers of overbank deposit separated by the
buried soils. In these sections the muds of the same age
are, therefore, facially diferentiated and occur at various levels.
In the widening sections, the flood plain structure is
analogous with that of Sandomierz Basin. A number of inserts
of alluvia of various age, associated with the meandering
river, occur here one beside the other at the same level.
Moreover, the overbank deposits show here a facial
differentiation related to the floodplain morphology and to
the distance from the active channel.
The braided Vistula river formed medium terraces by the
decline of the Pleniglacial, and likely at the beginning of
the Late Glacial. In the Allerod the concentration of the
channel took place and resulted in the river incision. A
very deep incision is indirectly confirmed by the lack of
the Late Glacial overbank deposits and the development
of eolian processes on the upper sandy terraces (11,020
BP). In the Atlantic the clayey overbank sediments (Mz =
7.0-7.5