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,
Bayou Corne sinkhole Oxy3 had begun to cave in. Louisiana Governor Bobby Jindal issued an evacuation order on August 3, 2012 after residents reported smells of crude oil throughout the town. Texas Brine investigated the situation by drilling a relief well and found that the outer wall of the salt dome had collapsed, allowing sediment to pour into the cavern and oil and gas to escape to the surface, causing the shaking and bubbles residents had observed. When first the sinkhole appeared, it spanned a hectare (2.5 acres). As of late February 2014, the sinkhole is 26 acres and growing. Texas Brine is