ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Vasilevichy-rnore than 30. Par all that the duration of the
storms may vary ftom minutes till days (the most long dusty
storm was observed in t. Vasilevichy in the April 1978­
38 hours). The wide development of the drying melioration
during the last 50 years promoted in the considerable
degree the growth of this phenomenon. Here prevailed
marsh-ridden mineral and peat and swampy soils before
drying. They were greatly watered and covered by natural
herbal vegetation and forests and that is why they were not
exposed to the action of the wind. The deep changes of the
water and airial, chemical, biological and other properties
occur by the drainage. In the peat and swampy soils the
destruction of the aggregates and the dispersion take place.
The lowering of the level of the first waterbearing horizon,
the decrease of the moisture capacity and the increase df
the filtration factor give rise to the drying-up of the upper
layers of soil, that cause their fast mineralization and destruction.
Dusty storms further the removal and accurnuladon
of the material and the creation of the eol-like forms
of the relief; eolian hills, blowing hollows, deflation fields.
HANNE H. CHRISTIANSEN
Nivation forms and processes in higharctic Greenland
Institute of Geography, University of Copenhagen,
0ster Voldgade 10,1350 Kebenhavn K, Denmark
In higharctic Greenland perennial and seasonal snowpatches
dominate large parts of the periglacial landscape and
control the distribution of the vegetation. Knowledge of
the combination of geomorphological processes and forms
that result from their existence therefore is important in
order to use the resulting landforms and sediments as indicators
of environmental change. The existence and distribution
of the snowpatches are mainly controlled by the dominating
winter wind direction and the amount of precipitation,
primarily the amount of snow, whereas the aspect
has less influence. This causes snowpatches to respond and
adjust quickly to climatic changes and their associated
landforms are correspondingly climatically sensitive.
Nivation forms and processes have been studied in a sedimentary
landscape at Zackenberg, NE Greenland. A
model containing the different processes transporting sediment
to and from the snowpatches is presented, and the
resulting landforms are shown. The dominating processes
are backwall sliding, niveo-eolian resedimentation, supraand
ennival sediment flows, niveo-fluvial erosion, development
of stone pavements and pronival solifluction. A
morphological complex of nivation hollows, associated niveo-fluvially
eroded channels and pronival alluvial cones or
depositional basins is typical. In the dry higharctic landscape'
with continuous permafrost, the snowpatches are controlling
the vegetation in large parts of the terrain below
the snowpatches, creating distinctive vegetation zones.
116
SHYH·JENd CRYI
the forming of main alluvial terraces in taiwan,
a continuously and quickly uplifting area
Department of Geography, National Kaohsiung Normal University,
Hoping 1st road; Kaohsiung, Taiwan
Terraces of five drainage basins and their 14C dates are
analyzed in this study. Those drainage basins are Liwu Rl"ver,
Lanyang River, Hoping River, Mougar River, located
in northeastern Taiwan, and Chaco River, located in
southwestern Taiwan. the analysis reveals a complex erosional
history of these areas during Holocene. Almost all
terraces of Liwu River, LatiyangRlver, Hoping River,
Mougar Rivet are alluvial terraces, It is very common that
the terraces' sediments are thicker than and the relieves ate
higher than 50 meters or even 100 meters. The terraces
with the highest relief (which is almost 400 meters) and the
thickest sediments (which is hear 200 meters) ate located
in Taosai River, a tributary of Liwu River. Nevertheless,
each drainage basin has different number of terrace;s fllghts,
In Choco River, all terraces are rock terraces and
meander scars, covered by thin sediments.
The continuing landmass uplifts with different rates and
the climatic changes since the latest Pleistocene have induced
rivers' downcutting, Downcutting produced many unstable
slopes. It must be the precondition of whether a large
quantity of sediments could be yielded from a drainage
basin in a short time span. The concentrated sediment
yield will cause river's aggradation. The highest average
downcutting rate is about 5cm/yr, found in Taosai River.
This may explain why the terraces of Taosai Rivet have the
highest relief, the thickest sediments, and the most number
of terrace's flights.
Climatic fluctuation might have no significant effect on the
forming of alluvial terraces during Holocene, unless there
were enough, unstable slopes in a drainage basin-Theretore,
climatic fluctuation is not the indispensable factor for
the forming of alluvial terraces. For instance, there is no alluvial
terrace in Chaco River. According to the 14C dates
and the sedimentologic and topographic properties of alluvial
terraces, the number of times of rivers being aggradated
in other four drainage basins is different. The time interval
that separated the prior aggradational stage and subsequent
stage in each drainage basin is clear. There were
four aggradational stages in Taosai River. Those stages are
about 6000 yr. BP, about 2500 yr. BP, about 1000 yr. BP,
and about 400 yr. BP. In upstream of Lanyang River, the
main terraces are alluvial fan terraces, located in the confluence
of tributaries and principal stream. Only three
main aggradational stages could be recognized. Those are
about 2000-1500 yr. BP; about 1000 yr. BP, and about 400
yr. BP.
Finally, whether a river had been aggradated seems to be
mainly controlled by the fluvial systems themselves; the
operating mechanisms, and the interaction among subsy-