Sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as the Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park in Kentucky, an underground stream or river may be visible across its bottom flowing from one side to the other. Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or in other soluble rocks, such as gypsum, that can be dissolved naturally by circulating ground water. Sinkholes also occur in sandstone and quartzite terrains. As the rock dissolves,
2010 Guatemala City sinkhole 2 left at least 15 dead, and a further 300 residents' lives were put at risk. Because of the role played by sewage pipes in the sinkhole's collapse, Sam Bonis, along with other geologists, has demanded that the government inspect the sewer system more regularly. According to officials, the sinkhole had similarities with another Guatemalan sinkhole which collapsed in 2007, which may also have been formed by ruptured sewage pipes. On a wider scale, immediately following reports of fatalities due to Agatha, a state of emergency was declared for Guatemala. On May 31, the government started to deploy national aid,