Question Earthority!

“Slums begin with bad geology. The shantytown periphery of Johannesburg, South Africa, for example, conforms unerringly to a belt of dangerous, unstable dolomitic soil contaminated by generations of mining. At least half of the region’s nonwhite population lives in informal settlements in areas of toxic waste and chronic ground collapse. Likewise, the highly weathered lateritic soils underlying hillside favelas in Belo Horizonte and other Brazilian cities are catastrophically prone to slope failure and landslides. Rio de Janeiro’s more famous favelas are built on equally unstable soils atop denuded granite domes and hillsides that frequently give way — with deadly results. Caracas, Venezuela, however, with a population of 5.2 million in 2005, is the soil geologist’s ‘perfect storm’: slums housing almost two-thirds of the city’s population are built on unstable hillsides and in deep gorges surrounding the seismically active Caracas Valley. At one time vegetation held the friable schist in place, but brush clearing and cut-and-fill construction have destabilized the densely inhabited hills and precipitated a radical increase in major landslides and slope failures — from less than one per decade before 1950 to the current average of two or more per month.” (03/29/06)