A 50 meters (164 feet) wide sinkhole has opened up last week in the Republic of Bashkortostan, Russia, near the village Novokulevo in Nurimanovsky District. Although such large sinkholes are rare, the region is known for its karst topography and numerous sinkholes.
This region (Ural Mountains), especially its western slope, where Bashkiria is located, has predominantly karst topography. It is composed of severely eroded sedimentary rocks (sandstones and limestones) that are about 350 million years old. There are many caves, sinkholes and underground streams. The karst topography is much less developed on the eastern slopes… [read more]