Karst is a landscape formed from the dissolution of soluble rocks including limestone, dolomite and gypsum. It is characterized by sinkholes, caves, and underground drainage systems. Karst topography is a geological formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone, dolomite, or gypsum, but has also been documented for weathering-resistant rocks, such as quartzite, given the right conditions.
Subterranean drainage may limit surface water with few to no rivers or lakes. Many karst regions display distinctive surface features, with cenotes, sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by one or more superimposed non-soluble rock strata. Some karst regions include thousands of caves, although evidence of caves large enough for human exploration is not a required characteristic of karst.
Laos ((i/ˈlaʊs/, /ˈlɑː.ɒs/, /ˈlɑː.oʊs/, or /ˈleɪ.ɒs/) Lao Language: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, pronounced [sǎː.tʰáː.laʔ.naʔ.lat páʔ.sáː.tʰiʔ.páʔ.tàj páʔ.sáː.són.láːw]Sathalanalat Paxathipatai Paxaxon Lao), officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south, and Thailand to the west. Its population was estimated to be around 6.5 million in 2012.