Mass Wasting in Haiti
February 12, 2010
Photographer: Rob Sheridan
Summary Author: Rob Sheridan
The photo above shows an example of mass wasting on a hillside near Cange, Haiti. The image was coincidentally taken about four hours before a 7.0 magnitude earthquake devastated the area on January 12, 2010, approximately 35 miles (56 km) to the south-southwest of Cange. This mass wasting event occurred long before the earthquake, and reveals the underlying limestone structure of the hills near the valley of the Artibonite River.Erosion takes many forms, including chemical, biological, and mechanical. Mass wasting is a dramatic form of mechanical erosion that occurs when a slope’s resistance to collapse is exceeded by gravity. This can happen in seconds, as in rock falls and landslides; over hours or days, as in mud flows or slumps; or over much longer intervals, as in mass creeps. Both natural and human factors can reduce a slope’s resistance leading to mass wasting. Chemical processes that can weaken rock include carbonation of limestone by water and atmospheric carbon dioxide. Mechanical forces include water and wind erosion, frost heaving, and seismic activity. Human activities leading to mass wasting include deforestation and slope undercutting.
Haiti’s central mountains contain large amounts of marine limestone elevated over millennia by the same tectonic processes that make all of the Greater Antilles prone to earthquakes. The limestone peaks and slopes have been compromised by a number of the above mentioned factors, and as a result, notable areas of mass wasting can be observed.