A sink hole is a natural depression or hole in the Earth’s surface which can be several hundreds of meters deep. It is formed either by karst or suffosion processes. The karst process happens when the carbonate rocks in the ground dissolves and then followed by caving-in. On the other hand, suffosion process happens when loose soil or non-cohesive materials lie on top of a limestone layer containing cracks, joints, or fissure. Rain and surface water will gradually erode these materials and sinkhole formation ensues. A sinkhole is also called as sink, shake hole, swallow hole, swallet, doline, or cenote.
There are many sinkhole formations and they are found worldwide – from remote jungles up to urban areas. Their sizes vary, as well as their forms and occurrence. Here are ten of the largest, most impressive and gorgeous sinkholes in the world.
Discovered by specialists in 1994, Xiaozhai Tiankeng is located in the Chongqing Municipality of China. It is the world’s largest and deepest sinkhole. The hole is 626 m long and 537 m wide. It has a depth of 511-662 m. Its area opening is 274,000 m2 and its volume is 119.348 million m3. There is a river underground (inside the sinkhole) that is approximately 8.5 km long.
There is a wide diversity of life at the bottom of the sinkhole. There are 1,285 registered species of plant including the rare gingko and many rare animals like clouded leopard. Recently, fast development in China has transformed the sinkhole into a tourism spot which consequently bring good profit to the rural community. (image source)
Dean’s Blue Hole
Located in a bay west of Clarence Town on Long Island, Bahamas, Dean’s Blue Hole is the deepest known sinkhole under the sea. Its name is taken from the family name of local landowners in the small bay. The bottom of the blue hole (a term for sinkholes filled with water) is larger with a diameter of around 100 m, making it one of the largest known underwater cave rooms in the world. (image source)
Over the years, the sinkhole has become the site of world-class free-diving sports. Its location is perfect since it is just next to the bank of a calm bay. (image source)
Named after scientist and explorer Alexander von Humboldt, Sima Humboldt (Sima Major) is a huge sinkhole located on the top of the plateau of Sarisariñama tepui in Bolivar State, Venezuela. It is around 314 m deep, with a volume of 21 million m3. Neighboring Sima Humboldt is another marvelous sinkhole – the Sima Martel, or Sima Menor. It is named after legendary speleologist Eduard Martel. The sinkhole is 284 m deep.
Both sinkholes are very unique. They are situated on top of the only forested tepui in the world. A tepui consists of Paleoproterozoan sandstone (quartzite) of Roraima formation and belong to the oldest exposed formations on Earth. Most tepuis do not have forest on their top but the one atop the Sarisariñama tepui is very dense and diverse. Since the walls of both sinkholes are insurmountable, there has developed a unique, small ecosystem inside them. Approximately 1.8 billion years, Sima Humboldt and Sima Martel are some of the oldest sinkholes in the world. (image source)
Great Blue Hole
Another impressive blue hole, the Great Blue Hole located off the coast of Belize in nearly perfectly round sinkhole. Its diameter is approximately 318 m, and its depth is at most 124 m. The sinkhole lies near the center of Lighthouse Reef which rises above the sea when the tide is low. There are no waves or currents inside the blue hole at depths of 18-20 m. However, the water suddenly turns brownish or enriched with hydrogen sulfide at 90-101 m deep. At the bottom of the Great Blue Hole, no life exists and only large pieces of limestone and sediments can be found. (image source)
The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System which is a World Heritage Site of UNESCO (United Nations Educational, Scientific, and Cultural Organization).
Known as the deepest known water-filled sinkhole in the world, El Zacatón belongs to the Zacatón system – a group of unusual karst feature located in Aldama Municipality in the northeastern state of Tamaulipas, Mexico. It has a depth of 339 m. The name of the sinkhole is derived from the free-floating islands of zacate grass which drift around the lake. These islands are formed from precipitated calcium carbonate and overgrown with the grass. (image source)
Water of El Zacatón is 29-30OC warm. It is slightly acidic at 6.9 pH level. El Zacatón is also unusual with its unique ecosystem. On rocks walls at 115-270 m depth, at least 9 new classes of microbes have been found. (image source)
El Zacatón is an important diving site with several scuba diving world records set there.
One of the largest sinkholes in the world, Crveno Jezero is located near the city of Imotski, Croatia. It is also called as Red Lake due to the reddish-brown color (caused by iron oxides) of the surrounding cliffs. It is approximately 530 m deep, with a width of 450-500 m and volume of 25-30 million m3. The diameter of the lake at the bottom of the sinkhole is around 200 m with a depth that runs from 280-290 m. Three small caves have been found near the water level of the lake. (image source)
Crveno Jezero contains several endemic species of organisms. One of which is the 12-cm long fish Delminichthys adspersus. This fish require extremely clean water present in the lake and are highly endangered.
Cave of Swallows
The Cave of Swallows, Sótano de las Golondrinas in Spanish, is an open air cave in the Municipaity of Aquismon, San Louis Potosi, Mexico. It owes its name from the myriad birds, specifically white-collared swifts, living on the holes on its cave walls. Entrance of the sinkhole is elliptical, measuring 49 by 62 m wide. But deep inside, it becomes much wider, around 303 by 134 m large at the bottom. The floor of the cave is a 333-m freefall drop from the lowest side of the opening, or 370-m drop from the highest side, making it the largest known cave shaft in the world. Because of its enormous size, the sinkhole is a popular extreme sports destination. Climbing, rappelling, and base jumping are just some of the sports undertaken there. (image source)
Sótano del Barro
Sótano del Barro, or “Cellar of Clay”, is located in Sierra Gorda mountains in the Arroyo Seo Municipality of Mexico. It has nearly vertical walls and rather looks like an elongated hole that is 455 m deep. The sinkhole houses the largest population of Mexican subspecies of military macaws. Flocks of these birds leave the cave early in the morning and return in evening. (image source)
Sótano del Barro is located amidst primeval tropical forest. At the bottom of its abyss, a unique ecosystem of ferns, shrubs, and even trees thrive. Because of this, it has been proposed as a UNESCO World Heritage Site. (image source)
Kingsley Lake is an almost perfect circular lake about 2,000 acres in North Central Florida. It is believed to be the oldest and highest lake in Florida. The lake is only 27 m deep and is a very stable lake. Its shape is nearly circular that it is tagged as Silver Dollar Lake. Kingsley Lake is famous for its clear waters, water skiing, and fishing. (image source)
The Blue Hole is an underwater sinkhole located on east of Sinai, north of Dahab, Egypt on the coast of the Red Sea. It has a depth of around 130 m. The Blue Hole has a 6-m deep opening called “the saddle” which opens out to the sea. There is also a 26-m long tunnel, known as “the arch”, of which its top lies at a depth of 56 m. The Blue Hole has been named as the “World’s Most Dangerous Dive Site” and “Diver’s Cemetery” because of the number of diving fatalities occurring there. Deaths are usually due to the diver’s futile attempt to find the tunnel through “the arch.” (image source)
Based on their depths, here are the ten largest sinkholes in the world:
- Xiaozhai tiankeng – China, Chongqing Municipality (662 m)
- Dashiwei tiankeng – China, Guangxi (613 m)
- Crveno Jezero – Red Lake – Croatia, Split-Dalmatia (530 m)
- Minye Sinkhole and Cave – Papua New Guinea, East New Britain (510 m)
- Haolong tiankeng – China, Guangxi (509 m)
- Kavakuna sinkhole – Papua New Guinea, East New Britain (480 m)
- Taipingmiao tiankeng – China, Chongqing Municipality (420 m)
- Sotano del Barro – Mexico, Queretaro (410 m)
- Xiashiyuan tiankeng – China, Chongqing Municipality (373 m)
- Daluodang tiankeng – China, Chongqing Municipality (372m)