ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

the rainy season 1995: a deep channel was eroded during
two typhoons. In addition, the river started meandering. It
is supposed that this reverse process will also occur in
other channels, after the major sediment sources are depleted.
The previously deposited sediments have been and
will be re-eroded and transported farther downstream by
hyperconcentrated flows and fluvial sediment transport.
Due to new watershed areas the river channels will not necessarily
adjust to pre-eruption conditions. Changes in the
water and sediment regime affect almost all river channels
for a distance of 50 to 100 km over the coming decades.
Beside an unprecedented magnitude of the natural processes
the socio-economic impacts are enormous: the eruption
hit one of the most populous areas of the Philippines which
serves as the granary for Luzon Island, including the capital
area of Manila. To date about 350 square kilometres
of agricultural land (mainly rice and sugar cane) are already
covered by lahar sediments. A total of 1.5 million
people are living within the endangered area. Nearly
70,000 families lost already their homes. The eruption itself
and the ongoing lahar activity constitute a major impact
to the economy of this Southeast Asian country.
ZBIGNIEW ZWOLINSKI
Mineral matter circulation within a polar geoecosystem,
south Shetland Islands
Quaternary Research Institute, Adam Mickiewicz University,
Fredry 10,61-701 Poznan, Poland
In the areas free from permanent glacier ice on the coast of
King George Island (the South Shetlands), mineral material
found in the Admiralty Bay geoecosystem comes primarily
from volcanic rocks. Additionally, it is supplied by
418
glacial transport from ice cups, aerosol transport from the
Admiralty Bay waters, littoral and aeolian transport (of various
ranges), and meteoric fallout. These sources, however,
are much less significant. Under the severe climatic
conditions bedrocks undergo high-magnitude weathering,
especially mechanical (disintegration, multigelation, exudation
etc.). The big amounts of rock waste thus produced
undergo denudation easily, and in effect are transported
outside their area of provenance. Among the dominant denudation
processes are mass movements, glacial erosion,
abrasion, fluvial erosion, and deflation. Each of them involves
its own type of waste transport: slope (including avalanches),
glacial, littoral, fluvial, and aeolian. Of lesser significance
are the periglacial and nival types of transport. In each
of these morphogenetic environments deposition and
redeposition takes place at various spatial and temporal
scales. As a result of diverse transformation of the waste in
morphogenetic and sedimentary environments, the Admiralty
Bay drainage basin receives material of different origin,
but mostly slope, glacial, fluvial, abrasion and aeolian.
The material delivered to the Admiralty Bay assumes three
forms: dissolved, suspended and solid. All three come as
glacial and fluvial, partly also abrasion, material. Solid material
derives exclusively from slope and aeolian processes.
The supply of solids is determined by the occurrence of
above-zero temperatures, and is only episodic unless produced
by glacial and fluvial processes. The glacial and fluvial
supply of dissolved and suspended material is continuous
even in the short periods of sub-zero air temperatures.
The supply of this type of material to the Admiralty
Bay basin is decisive for the primary production of biomass.
The waste reaching the Admiralty Bay can be transformed
in only one or in. many morphogenetic environments
with different hierarchical patterns.
Besides land mineral matter, there are huge amounts of
matter (mostly dissolved and suspended) reaching the Admiralty
Bay from glacier fronts and Bransfield Strait in
daily and seasonal cycles. Of no little significance is also
meteoric fallout and aeolian fallout of a global range.