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Dramatic erosional features, lavakas form in the deeply-weathered highlands of central Madagascar.

Report of
Science at Williams


Williamstown, Massachusetts

Lavakas are abundant in the highlands of Madagascar (25 sq.km. in some places). These remarkable features form by disintegration and collapse of deeply weathered rock in areas where the weathering profile is deep, the terrain is steep and hilly, and there is monsoonal rainfall. They are not caused by surface runoff (note that there are no streams or gullies entering into the ones shown here), but are related to subsurface groundwater movement. They form rapidly (days to weeks for initial growth), and then persist for decades, shedding debris and mudflows each rainy season. A collaborative research program involving Geosciences faculty and students from Williams and from Madagascar’s Université d’Antananarivo seeks to understand the factors that initiate lavaka formation. This NSF-funded project has demonstrated that, although human activities may cause enhanced lavaka activity, they are primarily driven by geological factors such as the orientation of slopes relative to prevailing weather patterns, slope steepness, and low-grade earthquake activity.

The Science Executive Committee wishes to express its gratitude to the extensive efforts of all the science departmental executive assistants in preparing contributions for this publication, and to Kate Fletcher, administrative assistant at the Science Center, for assembling this material in its final form.

Editor: Dr. Bryce Babcock
This document is printed on recycled paper.

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