ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

TERESA RAMIREZ-HERRERA
Active tectonics on the coast of a convergent margin,
Southwest Mexico
Instituto de Geografia, Unam, Ciudad Universitaria,
Coyoacan, 04510 D.P., Mexico
Active tectonics along the coast of the Pacific continental
margin of southwest Mexico is related to the subduction of
the Cocos and Rivera plates beneath this region. Differences
in the geometry of subduction and in the rate of convergence
between the Cocos and Rivera plates have been
reflected in differences in the rates of observed seismicity.
Remote sensing analysis and field evidence show that the
coastal morphology across the tectonic boundary of the
Mexican convergent margin reflects regional variations in
tectonic and seismic activity. The coastal zone of southwest
Mexico can be sub-divided on the basis of distinguishing
regional morphological characteristics. Six zones are identified:
1) the Jalisco zone, 2) the Colima zone, 3) the Michoacan
zone, 4) the Guerrero zone, 5) Oaxaca zone (P),
and the 6) Tehuantepec zone. A range of geomorphological
evidence, including marine terraces, elevated wave-cut
platforms, marine notches and river terraces indicates
uplift along the coasts of the Jalisco, Michoacan and Guerrero
zones. Differences in geomorphic characteristics
between the Jalisco, Colima and Michoacan zones reflect
changes in the style of subduction of the Rivera and Cocos
plates while variations in the coastal morphology near
Tehuantepec accord with transitions in tectonic and seismic
characteristics in this area.
JIWAN SINGH RAWAT & GEETA RAWAT
Adverse impact of human activities in geomorphic
processes and guidelines for their management in the
Central Himalaya, India
Laboratory of Environmental Geomorphology,
Department of Geography, Kumaun University Campus,
Almora, 263601 (Up), India
Anthropogenic activities, i.e. poorly managed agriculture
and reckless deforestation, and technogenic urban activities,
i.e. unplanned building and road constructions in the
fragile, geodynamically active, highest and the youngest
part of the earth, viz.,the Himalaya, have accelerated geomorphic
processes such as sheetwash erosion, channel erosion,
(i.e., suspended, dissolved and bed load), overland
flow alarmingly resulting in catastrophic floods, frequent
prodigal landslides during the monsoon rains; and deple-
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tion of groundwater storage, drying up of the natural
springs and steadly dwindling of streams base flows during
summer. The intensity and pattern of the geomorphic processes
in the Himalaya is poorly understood or unexplored.
Some recent studies (Rawat & Rawat, 1994 a, b) reveal
that the rate of channel erosion has been accelerated five
(in deforested land) to nine times (in agricultural land) higher
in the anthropogenically disturbed systems in comparision
to the erosion rates in the natural system. These studies
have also indicated that in the most disturbed agricultural
land 60% of the annual runoff occurs in a single
month of July-the month of the heaviest rainfall. However,
under natural conditions in the oak and pine mixed forest
only about 23 % of the total annual flow occurs in July. In
April, the driest and hottest month measurements indicate
that high amounts of runoff (i.e., 308 cubic meter per
square kilometer per year) in the natural system while runoff
amounts low (108 cubic meter per square meter per
year) in the most disturbed agricultural land.
In view of the changing environment of the fragile Himalaya
caused by the rapid changing behaviour of the geomorphic
processes due to the human activities - a long
term research project funded by the Department of Science
and Technology, and Department of Forest and Environment,
Government of India, was launched in 1990 for
the careful monitoring of geomorphic processes and to formulate
guidelines and strategies for the sustainable development
of water and land resources, in particular and for
the regeneration of the entire environment, in general.
This paper includes the detail account of the new scientific
strategy of the study, instrumentation network of the six
permanent field laboratories developed in the micro watersheds
to study the geomorphic processes under varied ecological
conditions, preliminary results of the project and
some major guidelines for the sustainable development of
water and land resources of the fragile Himalaya.
BRICE R. REA 1, DAVID J.A. EVANS 2 & DOUGLAS 1. BENN 3
Bedrock quarrying beneath deforming bed glaciers
1 School of Geosciences, Queens University Belfast,
Belfast BT7 INN, UK
2 Department of Geography & Topographic Science,
University of Glasgow, Glasgow G12 8QQ, UK
3 Department of Geography, University of Aberdeen,
Aberdeen AB24 3UP, Scotland, UK
Quarrying of bedrock is one of the dominant processes of
subglacial erosion. It is traditionally assumed to occur only
beneath glaciers with an ice-rock bed. This paper investigates
the potential for quarrying beneath a wet-based glacier
where a thin or patchy deforming till layer overlies a
hard rock bed. This is based upon investigations at con-