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The Red Lake sinkhole in Croatia. A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are also known as shakeholes, and to openings where surface water enters into underground passages known as ponor, swallow hole or swallet.
Description. Formed in Carboniferous / Permian limestone, the main Sơn Đoòng cave passage is the largest known cave passage in the world by volume – 3.84 × 10 7 m 3 (1.36 × 10 9 cu ft), according to BCRA expedition leader Howard Limbert. It is more than 5 kilometres (3.1 mi) long, 200 metres (660 ft) high and 150 metres (490 ft) wide.
The Xiaozhai Tiankeng is 626 meters (2,054 feet) long, 537 meters (1,762 feet) wide, and between 511 and 662 meters (1,677 and 2,172 ft) deep, with vertical walls. Its volume is 119,349,000 m³ and the area of its opening is 274,000 m 2. This material has been dissolved and carried away by the river. The sinkhole is a doubly nested structure ...
Kilsby sinkhole – in Mount Gambier, Southern Australia. Koonalda Cave – a cave located in the Nullarbor Plain in South Australia. Little Blue Lake – water-filled doline located near Mount Schank in South Australia. Numby Numby – a sinkhole located 25 to 30 kilometres (16 to 19 mi) west-northwest of Borroloola in the Northern Territory.
The history of Vietnam can be traced back to around 20,000 years ago. The first modern humans to arrive and settle in the area of modern-day Vietnam are known as the Hoabinhians, who can be traced as the ancestors of modern-day Negritos. Archaeological findings from 1965, which are still under research, show the remains of two hominins closely ...
The ownership of the islands remains hotly contested. The People's Republic of China (PRC) on mainland China, Vietnam, and the Republic of China (ROC) on Taiwan all claim de jure sovereignty, although the PRC has had de facto control of the archipelago since the Battle of the Paracel Islands in January 1974.
The sinkhole was formed in karst terrain, which means rock below the surface can easily be dissolved by groundwater circulating through the bedrock. [5] The large hole measures over 1,000 feet in length, almost 500 feet wide and 630 feet deep, with a volume of over 176 million cubic feet. [ 6 ]
Caldera. A caldera (/ kɔːlˈdɛrə, kæl -/ [1] kawl-DERR-ə, kal-) is a large cauldron -like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly ...