Cerro Autana

Cerro Autana is a tepui, a flat-topped table mountain, on the western edge of the Guiana Shield in Amazonas state, Venezuela, near the Colombian border, rising to about 1,220 meters with a narrow base, nearly vertical walls and a flat summit. The mountain is the eroded remnant of a once much larger sandstone plateau that formerly covered the granite basement rock between the northern Amazon Basin and the Orinoco River. Water percolating along joints and bedding planes dissolves the silica cement holding the sandstone together, causing quartzite blocks to disaggregate and collapse; this process has carved extensive cave systems through the mountain and produced dramatic waterfalls along its scarps.