ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

ecent decades as it was associated to remarkable depletion
of cultivated hind.
Field investigations on gully morphology and their genetic
processes were carried out in two study areas of Ethiopia,
representative of different geological, geomorphological
and other environmental conditions. They are: a) the Lakes
Region in the Rift Valley north of Shashamene (elevation
between 1,700 and 2,000 m a.s.l.; annual rainfall ranging
from 700 to 1,100 mm; gully occurrence mainly on colluvial
foot-slopes at the base of fault scarps, alluvial and lacustrine
deposits); b) Adi Kolen and Mai Maikden, south
and north of Mekele respectively, Tigray (sedimentary
rocks, Antalo limestone and Agula shales; annual rainfall
around 500..800 mm; mainly vertisols; in both areas gullies
originated by piping processes are very common. These
gullies develop on both footslopes and flat swampy or
overbank deposits.
Three main types of gullies were identified on the basis of
their morphological characteristics. They are: 1) embryo
gullies, which generally develop on gentle slopes (gradient
less than 0.05-0.1) and whose cross-section area increases
from an upstream minimum to a maximum, at approximately
their mid length, and decreases again to a minimum at
their downstream edge; 2) headwater gullies, formed by
deep erosion processes typically migrating upslope. These
gullies make up the main headwater sediment sources of
larger river systems; 3) bank collapsed gullies. They are
gullies whose almost vertical banks may have partially collapsed
filling, locally entirely, the incised channel. Multiple
cycles of filling and stream incision were also observed.
In order to investigate the main causes originating the different
types of gullies, data on geomorphology, land use,
soil characteristics and hydraulic geometry were collected
in the field. From the analysis of field and climatic data hypotheses
on gully formation in the study area were derived.
The temporal evolution of the gullies in the study areas
and the main factors originating them are illustrated and
discussed in this presentation.
OGBAGHEBRIEL BERAKHI 1, LUDOVICO BRANCACCIO2,
GILBERTO CALDERONI\ MAURO COLTORTI 4
,
FRANCESCO DRAMIS 5 , BELAYTEGENE 1 & MOHAMMAD UMER 6
Geomorphological and sedimentary records
of Holocene climatics changes and human impact
in the Highlands of Northern Ethiopia
1 Department of Geography, University of Addis Ababa, p.o. box 1176,
Addis Ababa, Ethiopia
2 Dipartimento di Scienze della Terra, Universita di Napoli Federico II,
largo S. Marcellino 10,80134 Napoli, Italy
3 Dipartimento di Scienze della Terra, Universita La Sapienza,
p.le Aldo Moro 5,00185 Roma, Italy
4 Dipartimento di Scienze della Terra, Universita di Siena,
via delle Cerchia 3, 53100, Siena, Italy
5 Dipartimento di Scienze Geologiche, Universita di Roma Tre,
via Ostiense 169,00154 Roma, Italy
6 Department of Geology and Geophysics, University of Addis Ababa,
p.o. box 1176, Addis Ababa, Ethiopia
The highlands of Welo and Tigray (northern Ethiopia), at
elevations generally exceeding 2.000-2.500 m a.s.l., with
maximum elevations above 4.000 m a.s.l., may be considered
one of the tropical areas most affected by soil erosion
and land desertification. The climatic characteristics of this
region (with 15°C to 25 °C annual temperatures and 500
to over 1.200 mm annual rainfall, mostly concentrated in
summer months) are compatible with a Juniperus and Podocarpus
forest, and by mixed deciduous and Juniperus
woodland (with subordinate savannah). By contrast, arboreal
vegetation is lacking at present, except for a few trees
(Juniperus, Olea and Ficus), generally clustering around
churches, monasraries and in less accessible sites.
Since the second half of II millennium B.C., the area has
sustained the impact of human activities which reached
their maximum development during the kingdom of Aksum
(II century B.C.-800 A.D.) and, subsequently. underwent
a sudden decrease, probably as a consequence of
the kingdom's decline.
This paper discusses the results of geomorphologic-stratigraphic
investigations carried out on Holocene deposits in
the highlands of Welo and Tigray (northern Ethiopia). Radiocarbon
datings of peaty deposits and buried soils allowed
to establish that during Early-Middle Holocene (at
least between 8,300 ± 100 yr B.P. and 3,880 ± 70 yr B.P.)
more humid climatic conditions favored soil formation and
forest development in the area. Later, generalized slope
erosion caused the burial of the soils under thick layers of
colluvial and alluvial sediments. This may be related to a
progressive reduction of vegetation cover due to the onset
of drier climatic conditions even though, the finding of artifacts
and prehistoric settlements in the area also suggest
some influence of human impact.
A more recent phase of soil formation, possibly connected
with a minor shifting of climate towards wetter conditions,
is testified by the dating of buried soils in Tigray (1,250 ±
60 yr B.P.; 970 ± 60 yr B.P.). Subsequently, widespread
slope degradation, likely related to human activity, followed.
The impact of human pressure on the environment
has continued till the present times (specially during the
last decades), being responsible for the present barren
landscape.
IVAR BERTHLING 1, TROND EIKEN 2 , BERND ETZELMULLER 1
& JOHAN LUDVIG SOLLID 1
The relationship between strain and morphology
on a solifluction lobe, Finse, southern Norway
1Department of Physical Geography, University of Oslo,
p.o. box 1042, Blindern, N-0316 Oslo, Norway
2 The Norwegian Polar Institute,
p.o. box 5072, Majorstua, N-0301 Oslo, Norway
This paper discusses the relationship between surface
strain and morphology on a solifluction lobe, localized at
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