ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

MARIA LAURA IBSEN & EDWARD N. BROMHEAD
Head scarps and toe heaves
School of Civil Engineering, Kingston University,
Penrhyn road, Kingston upon Thames, Surrey KT1 2EE, UK
Where the historical archival record is poor, evidence of
the temporal occurrence and frequency of mass movement
must be derived from the identification and investigation
of the landslides themselves. Inevitably, the geomorphologist
must learn to recognise the significance of subtle elements
of old landslide events, in order to correctly anticipate
the necessary scope and scale of sub-surface geotechnical
investigations.
Features described loosely as «head scarps» and «toe heaves»
relating to a variety of landslide types are described in
this paper, with examples drawn from small and medium size
landslides. Accurate recognition of these features permits
preliminary assessments of slip surface position and shape
to be made using general guidelines. Related problems associated
with graben geometry are also discussed, and the observations
of Cruden & Thomson (1991) are extended.
It is often the case that the head scarp of a developing
landslide is easier to distinguish than the toe heave. The
reasons for this are discussed. The paper shows that the
movements at both the head and toe of a landslide failure
have virtually the same dimensions, indicating that the material
has merely been displaced downslope.
Some of the results of this study explain the development of
the composite landslide type termed a «slump earthflow».
During the production of 'Landslide Recognition' (Dikau &
alii, 1996), the authors came across the problem of defining
the characteristics of a slump-earthflow. It was considered
essentially a complex failure comprising an upper rotational
section which extends into a mudslide. The reasons for this
development are discussed in the paper in the context of
the post initial failure of the toe of a rotational slide. The
paper concludes with a number of observations on the degradation
with time of head scarps and toe heaves, and the
problems of assessing the temporal occurrence and frequency
of movement from such geomorphological features.
MIHAl IELENICZ \ ILEANA PATRU 2 & CORNEL TUDOSE 3
Les glissements de terrain de la Roumanie: etude de cas
1Faculte de Geographie, Universite de Bucharest,
str. Masina de Paine nr. 1, Sc. 1, Ap. 42, Sect. 2 Bucharest, Roumanie
2 Faculte de Ceographie, Universite de Bucharest, bulevardul
Stirbei Voda Bl. A4, Er], II, Apt. 13, Craiova Dolj, 1100, Roumanie
3 Faculte de Geographie , Universite de Bucharest,
str. Mihai Eminescu 5,2041 Urlati Prahova, Roumanie
Les glissements de terrain se produissent dans presque
toutes les regions de la Roumanie. La diversite des facteurs
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(la structure, les roches, les pentes, les defrichements, Ie
degre d' humectation des depots), determine des differences
dans la repartition des glissements au niveau du pays.
L'etude mis en evidence les regions ou les glissements ont
une grande ampleur dans la modelation des versants (Les
Subcarpates, Ie Plateau de la Moldavie, la Depression de la
Transylvanie) et des regions ou les effets des glissements
sont reduites (les plaines du sud et l'ouest). En fonction
des types et de leur frequence on distingue des regions
avec une grande, moyenne et petite frequence des glissements
de terrain.
CATHERINE IMBANGULAYA IKHILE
Seasonal variation in water quality of Orle River
Basin, S.W. Nigeria
University of Benin Demonstration Secondary School,
(UDSS) P.M.B. 1154, Benin City, Nigeria
The Orle River Basin is one of the major River Basins providing
both domestic and industrial water for communities
around the northeastern fringes of South Western Nigeria.
The seasonal variation in water quality of Orle River and
its tributaries was based on samples obtained fortnightly
from November 1987 to June 1988. The drainage basin is
underlain by both Basement Complex and Sedimentary
rocks. This geological difference in the terrains has been
observed to affect the toxicity and other physico-chemical
characteristics of the rivers within one season and from
season to season.
The investigation revealed that true colour, total solids, chloride,
sodium, biochemical oxygen demand (BOD 5 ) and dissolved
oxygen (DO) vary significantly with seasonal changes.
True colour, water temperature, taste, chloride, DO, BOD 5
and COD show increase in the wet season and decrease in
the dry season. Conversely, air temperature, pH, total solids,
sodium, potassium, calcium, magnesium, iron, aluminium,
silica, nitrate, sulphate and total hardness show increase in
the dry season and decrease in the wet season. The values of
some of the parameters are beyond tolerable limits.
The degree of pollution observed in the rivers constituting
the Orle River Basin is sufficiently significant enough to
necessitate pre-treatment of the Basin water prior to domestic
and industrial uses. Presently, the natives treat the water
with alum before use, but this practice is not a sufficient
biophysico-chemical treatment required to make the
water safe for consumption.
ALEXANDER V. ILYIN
The world ocean floor relief evolution problem
N.N. Andreyev Acoustics Institute,
4 Shvernik st., 117036 Moscow, Russia