Within the heart of the Malagasy Hauts-Plateaux, the rolling grasslands are pitted by deep incisions locally referred to as lavaka (‘hole’ in Malagasy). These mass failure features provide vast quantities of terrestrial matter to local freshwater arteries, accounting for over 80% of the annual sediment load of the Betsiboka River. The collapse of the overlying laterite exposes a comparatively nutrient enriched saprolite layer, and in later stages of lavaka evolution, these conditions provide the substrate for a relatively species-rich microcosm isolated amongst the homogenous grasslands, as can be seen here.
The imagery evoked from this lavaka is unmistakeable; the cascading vegetation draining through the neck of the hourglass as time progresses, mirroring the cycles of erosion and stabilisation so characteristic of these dynamic landscape features.
Description by Trent Marwick, after the description on imaggeo.egu.eu.
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