Lavaka
Lavaka (from Malagasy for hole ) is a form of soil erosion that occurs particularly in Madagascar .
Lavakas are on average 80 m long, 40 m wide and 15 m deep erosion gorges with a very narrow outflow area. They form on steep, convex slopes due to the sudden escape of groundwater and the associated liquefaction of the water-saturated soil. In the highlands of Madagascar up to 25 lavakas per km² have been counted.
Prerequisites for the formation of lavakas are seasonal tropical heavy rain, deep weathering of the rock substrate (up to 100 m thick saprolites ) and sparse vegetation (mostly only grasses). Further damage to the vegetation cover by cattle steps or the construction of unpaved roads favor the formation of lavakas. Shocks caused by weak earthquakes are assumed to be the trigger for the sudden leakage of groundwater.
literature
Wells, NA & Andriamihaja, B. (1993). The initiation and growth of gullies in Madagascar: are humans to blame? Geomorphology 8 , pp. 1-46.