Karst is a topography formed from the dissolution of soluble carbonate rocks such as limestone, dolomite, and gypsum. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground.
Subterranean drainage may limit surface water, with few to no rivers or lakes. Buried karst in the stratigraphic column is important in petroleum geology as about 50% of the world’s hydrocarbon reserves are hosted in carbonate rock, and much of this is found in porous karst systems.
Karst is most strongly developed in dense carbonate rock, such as limestone that is thinly bedded and highly fractured. Karst is not typically well developed in chalk, because chalk is highly porous rather than dense, so the flow of groundwater is not concentrated along fractures. Karst is also most strongly developed where the water table is relatively low, such as in uplands with entrenched valleys, and where rainfall is moderate to heavy. This contributes to the rapid downward movement of groundwater, which promotes dissolution of the bedrock,
Chemistry of dissolution. The carbonic acid that causes karst features is formed as rain passes through Earth’s atmosphere picking up carbon dioxide (CO2), which readily dissolves in the water. Some of the dissolved carbon dioxide reacts with the water to form a weak carbonic acid solution, which dissolves calcium carbonate. The oxidation of sulfides leading to the formation of sulfuric acid can also be one of the corrosion factors in karst formation.
Morphology. The karstification of a landscape may result in a variety of large- or small-scale features both on the surface and beneath. On exposed surfaces, small features may include solution flutes, runnels, limestone pavement, kamenitzas collectively called karren or lapiez. Medium-sized surface features may include sinkholes or cenotes (closed basins), vertical shafts, foibe (inverted funnel shaped sinkholes), disappearing streams, and reappearing springs.
Large-scale features may include limestone pavements, poljes, and karst valleys. Mature karst landscapes, where more bedrock has been removed than remains, may result in karst towers, or haystack/eggbox landscapes. Beneath the surface, complex underground drainage systems (such as karst aquifers) and extensive caves and cavern systems may form.
Erosion along limestone shores, notably in the tropics, produces karst topography that includes a sharp makatea surface above the normal reach of the sea, and undercuts that are mostly the result of biological activity or bioerosion at or a little above mean sea level. Some of the most dramatic can be seen in Thailand’s Phangnga Bay and Halong Bay in Vietnam.
Calcium carbonate dissolved into water may precipitate out where the water discharges some of its dissolved carbon dioxide. Rivers which emerge from springs may produce tufa terraces, consisting of layers of calcite deposited over extended periods of time. In caves, a variety of features collectively called speleothems are formed by deposition of calcium carbonate and other dissolved minerals.
Kegelkarst, salt karst, and karst forests. Kegelkarst is a type of tropical karst terrain with numerous cone-like hills, formed by cockpits, mogotes, and poljes without strong fluvial erosion processes. This terrain is found in Cuba, Jamaica, Indonesia, Malaysia, the Philippines, Puerto Rico, southern China, Myanmar, Thailand, Laos and Vietnam.
Karst areas tend to have unique types of forests. The karst terrain is difficult for humans to traverse, so ecosystems are often relatively undisturbed. The soil tends to have a high pH, which encourages growth of unusual species of orchids, palms, mangroves, and other plants.
Aquifers. Karst aquifers typically develop in limestone. Surface water containing natural carbonic acid moves down into small fissures that lead to progressive enlargement of openings forming a conduit system that drains the aquifer to springs. Groundwater flow rate in karst aquifers is much more rapid than in porous aquifers. Groundwater in karst areas is easily polluted as Karst formations are cavernous and highly permeable, resulting in reduced opportunity for contaminant filtration.
Farming in karst areas must take into account the lack of surface water. The soils may be fertile enough, and rainfall may be adequate, but rainwater quickly moves through the crevices into the ground, sometimes leaving the surface soil parched between rains.
SOUTH CHINA KARST A UNESCO World Heritage Site since June 2007, this spans the provinces of Chongqing, Guangxi, Guizhou, and Yunnan. It is noted for its karst features and landscapes unrivalled in terms of the diversity of its karst features and landscapes. The region is recognized as the world’s type area for karst landform development in the humid tropics and subtropics. The property also includes many large cave systems with rich speleothem deposits.
The karst features and geomorphological diversity of the South China Karst are widely recognized as among the best in the world. The region can be considered the global type-site for three karst landform styles: fenglin (tower karst), fengcong (cone karst), and shilin (stone forest or pinnacle karst).The landscape also retains most of its natural vegetation, which results in seasonal variations and adds to the outstanding aesthetic value of the area. It constitutes the world’s premier example of humid tropical to subtropical karst: one of our planet’s great landscapes.
Lunan Stone Forest, Yunnan. Near Shilin and approximately 90 km from the provincial capital Kunming, the tall rocks seem to arise from the ground reminiscent of stalagmites, with many looking like petrified trees, thereby creating the illusion of a forest made of stone.
These formations, caused by the weathering of limestone, are believed to be over 270 million years old and are a tourist attraction for both overseas and domestic tourists, with bus tours bringing tourists from Kunming. There are also a number of hotels in the area.
The Stone Forest area was a shallow sea some 270 million years ago. Extensive deposits of sandstone overlain by limestone accumulated in this basin. Uplift and later, exposure to wind and running water shaped these limestone pillars. Macroscopic fossil remains are seldom seen.
GUIZHOUU KARST LANDSCAPES
Guizhou has been labelled as egg-box topography – crowded sharp summits with intervening depressions largely devoid of integrated valley systems.
Li River 2½ hour boat ride on the way to Yangshou for 280¥. The half hour bus ride turned into an hour and a half on pot-holed dirt roads to the river and the small bamboo boats (actually plastic that looked like bamboo). We put-putted down the river at a snail’s pace through magnificent karst scenery of cliff faces, pinnacles and towers. The Chinese 20¥ bill has a scene from the river. After the boat ride, we boarded 10-passenger golf carts to Xingping and then a bus to Yangshuo.
Xingping is 27 km upstream from Yangshuo on the Li River. A prominent peak overlooks the village, topped with a lookout that can be climbed. 
Yangshou (pop 310,000) has karst towers much closer than in Guilin. 
Zhijin Cave (near Minzhai Village, 120 kilometers from Guiyang) is a huge cave with 150 scenic spots, 19 halls and 49 chambers that are open. The average height of the cave is 46 meters and the highest spot is 168 meters and is noted for its stalactites, stalagmites, and the clear blue water in its lakes, rivers and waterfalls.
More than 12 kilometers long, the largest hall is 173 meters wide and 150 meters high. It is like a vast underground palace with a superb array of karst formations – stone curtains, stalactites, stalagmites, stone pillars and stone flowers. The “Silver Rain Tree” is a 17-meter-tall rare flower-like transparent crystal; the gold silver tower. 
Guizhou: the Land of Waterfalls
Huanggoushu Waterfall: Asia’s Largest Waterfall is 47 kilometers south of Anshun City and 137 kilometers from Guiyang) – 77.8 meters high, and 101 meters across. In the middle of the falls water cascades over a cliffside cave, which can be reached on a slippery trail for an inside view of the falls.
The waterfall, along with 18 minor but equally beautiful waterfalls, such as the Luositan Waterfall, Silver-Chain Waterfall and Dishuitan Waterfall, is also known as the Huangguoshu Waterfalls Cluster. It was included into the Guinness Book of World Records in 1999 as the world’s largest waterfall cluster. Huangguoshu Waterfall is the only waterfall in the world that can be viewed from above, below, front, back, left and right.
Guanling Waterfall on the Baling River Canyon, there are seven grades with the total fall of 410 meters. Each grade has its special features and charms. 
Na Daguan Waterfall has 18 grades over 140 meters.
Getu River Scenic Spot on the upper reaches of the Hongshui River 76 km from the city proper of Anshun, It has suspension coffins, tombs in caves, ethinic customs and lifestyle.and the world’s second largest undergorund chamber.
Xiangshuidong Cave at 215m, is the deepest shaft of underground rivers with the final troglodytism tribe in human history — Miao Village in Zhongdong Cave. The cliffs along both sides of the Getu River are home to the hanging coffins of the Miao people. Hundreds of thousands of ancient coffins are placed in the caves on the cliffs. 
Libo Zhangjiang Scenic Spot (Libo County, 120 kilometers south-southeast of Guiyang) has the Small Seven-hole Bridge, Large Seven-hole Bridge, Shuichun River Scenic Area and Zhangjiang River Scenic Area with wide array of waterfalls, streams, lakes, forests, fantastic caves and the ethnic cultures of the Shui, Bouyei, Miao and Yao people.
.
Maolan (in Libo County) is in a beautiful karst area. There are many ethnic groups living here, including Bouyei, Shui and Yao. Maolan Karst Nature Reserve has forest covering 91.6 percent, 500 kinds of trees, various wild animals, virgin forest, karst caves and waterfalls.
THAILAND KARST
Phang Nga Bay is a 400 km2 bay in the Andaman Sea in southern Thailand. Limestone cliffs with caves, collapsed cave systems, and archaeological sites are found. Around 10,000 years ago, when sea levels were lower, it was possible to walk from Phuket and Krabi.
Phang Nga is a shallow bay with 42 islands, comprising shallow marine waters and intertidal forested wetlands, with at least 28 species of mangrove; seagrass beds, coral reefs and t least 88 bird species are also present.
Krabi
VIETNAM
Tan Lo Cave (a 2-day/1-night swim through several caves). About 100km north of the National Park, we passed through an amazing karst landscape – sheer walls, broken ridge lines and karst pinnacles. Hung Ton Cave had a big drop with a ladder and then a long swim. After swimming across a river, we entered Kim Cave, discovered first in 2012. This one involved 3 moderate swims. We were wearing a life jacket and had a pack carrying our stuff and providing flotation. After a long hike we entered Tan Lo Cave with wonderful formations – large draperies, soda straws, and marvelous fern like formations. This was a hike in and out with no swimming. We camped outside Ken Cave with its rushing waterfall. Sleeping was in a hammock and I was out for 11 hours.
The Polish couple on the trip got into the rice moonshine and were so hung over the next morning, they skipped the Ken Cave. After a 200m swim, we explored another half kilometer of dry cave with some good formations at the end and then had the same swim back. It was a rough hike back across rugged karst mountains.
The guide, food, caves and company were all excellent, well worth the rather expensive $250 cost. We crossed many flat fields on the way back – all cultivated for crops other than rice. It seems women do all the work and men ride around on their motorbikes, play cards and checkers, and drink rice wine. After the fields were plowed they were breaking up the clods by standing on a simple frame of 2 boards pulled by a water buffalo.
Phong Nha Ke Bang National Park has pristine jungle with over 90% primary forest and hundreds of caves in the oldest karst landscape in SE Asia, including the largest cave in the world.
I went on a one day national park tour. We stopped at several road side viewpoints to see the amazing landscape and get a full run-down on how the war was fought in this area. It was the start of one of the Ho Chi Minh trails. The area was heavily bombed and defoliated with agent orange but seems to have recovered except for large amounts of unexploded ordnance.
Paradise Cave has boardwalk through the first 1 1/2kms displaying marvelous formations in this huge cave.
Dark Cave, Named for the harder black limestone forming most of the walls. After a kayak ride to access the cave, we had a short wade and entered a narrow side canyon and waded through and climbed over several hundred yards of wet mud up to our mid-thighs and then returned the same way.
I think the guides wanted us to start a mud fight but few took the bait. It was then a swim out and back in a big pool to wash off all the mud.
Sơn Đoòng Cave. Located near the Laos–Vietnam border, Hang Sơn Đoòng has an internal, fast-flowing subterranean river and the largest known cave passage in the world by volume.
Hang Sơn Đoòng was found by a local man named in 1991. The whistling sound of wind and roar of a rushing stream in the cave heard through the entrance as well as the steep descent prevented the local people from entering the cave.
Only in 2009 did the cave become internationally known after a group of cavers from the British Cave Research Association conducted a survey in Phong Nha-Kẻ Bàng. Their progress was stopped by a large, 60-metre (200 ft) high flowstone-coated wall, which was named the Great Wall of Vietnam. It was traversed in 2010 when the group reached the end of the cave passage.
The main Sơn Đoòng cave passage is the largest known cave passage in the world by volume – 38.4×106 cubic metres. It is more than 5 kilometres long, 200 metres high and 150 metres wide. Its cross-section is believed to be twice that of the next largest passage, in Deer Cave, Malaysia. It has 2 large dolines, areas where the ceiling of the cave has collapsed and allow sunlight to enter resulting in the growth of trees.
The cave contains some of the tallest known stalagmites in the world, which are up to 70 m tall. Behind the Great Wall of Vietnam were found cave pearls the size of baseballs, an abnormally large size.
In early August 2013, the first tourist group explored the cave on a guided tour at a cost of US$3,000 each. Permits are required to access the cave and are made available on a limited basis, with 1000 permits available for the 2019 and 2020 season, which runs from February to August. As of 2017 only Oxalis Adventure Tours have permission to enter the cave for tourism purposes. (Maybe this cave is open now without the expensive tours).
Cat Ba Island, about 35 km south of Halong Bay with a national park and a much more relaxed pace. I had an amazing series of transportation links without a 30-second delay between any of them – a motorcycle to Leong Yen Bus Station, a 2-hour bus to Haiphong (the third largest city in Vietnam), a motorcycle to Ben Binh Harbour, bus 30 minutes south to Dinh Vu, 30-minute fast boat to Cat Ba Island and another 30-minute bus across the island to Cat Ba Town.
Cat Ba Island, Rugged, craggy and jungle-clad, the island is Vietnam’s adventure and ecotourism centre. It was declared a National Park in 1986 to protect the rare golden-haired Langur, the world’s rarest primate, Cat Ba is a nice alternative way to see the karst formations of Halong Bay, one of the New Seven Natural Wonders of the World, while avoiding all the dodgy scams involved in seeing the bay from Halong City. Lan Ha Bay has 300 or so karst islands, very much an extension of Halong Bay but with beaches, fewer people, and less trash. I went on a one-day boat tour of the bay visiting a cave that wound through an island, kayaking, and swimming. The forested, vertical-walled karst islands are quite spectacular
.
CENOTES YUCATAN MEXICO
Cenotes are deep underwater sinkholes. The Yucatan is flat and low and is made of limestone bedrocks which allow the rainwater to filtrate the soil allowing huge deposits of water and underground rivers. It was the residence of the gods, who had direct influence over human affairs. Perhaps none of the area’s features was of more sacred importance than the cenotes, the distinct Yucatán sinkholes where the ancients believed it was possible to commune with the rain god Chaac.
The Maya used the cenotes not only as precious and unique sources of water but also as sacred places for their religious ceremonies.
Homun and Anillo de los cenotes (cenote ring).
To the ancient Mayans, this teeming landscape of the Yucatán
Some 6,000 of these cenotes, whose name derives from the Mayan ts’onot, cover the peninsula, an abundance partially owed to the geological impact of the dinosaur-destroying Chicxulub asteroid that hit the area 65 million years ago. Mayan settlements were typically established in the vicinity of cenotes, for both practical purposes, namely a water source, and ritual purposes, such as sacrificial offerings to Chaac and calculation of harvests.
The Cuzumá cenotes are actually located in a remote jungle area a considerable distance from the idyllic town. Getting there is half the fun. From the roadside parking area, access to the cenotes is restricted to a ride on a horse-driven Decauville train track system. Here is a remnant of the henequen (agave rope) industry that briefly made nearby Mérida one of the wealthiest cities in the 19th-century world. Now the ghost rails that once hauled the “green gold” of the Yucatán to the ports of Mexico lug sweaty tourists to the cenotes.
Cenotes Chelentún, Chansinic’Ché, and Bolón-Chohol, roughly translated as “lying stone,” “ant tree,” and “bat hole,” are all known as “cántaro” style cenotes. The word describes cavern-like cenotes with an entrance narrower than the width of the water below. The most impressive of the three is the massive Bolón-Chohol, something of a naturally sculpted dome cathedral of water, rock, and vine. Once the 50-foot vertical ladder climb into apparent blackness is cleared, crystal blue waters, illuminated by a small hole in the ceiling, stretch out like a glass floor. Thirsty tree roots dip down from the dome-like ceiling for a drink; they mingle with tooth-like stalactites. It’s hard not to join the Mayans in imagining this as a dwelling place of the divine.
Cenote Chelentún is the smallest, shallowest of the three, and should take up the least of a visitor’s time. Chansinic’Ché, however, is almost as impressive as Bolón-Chohol, and its waters are comparably as deep and blue. Cenotes stay the same general temperature all year—in the 70s Fahrenheit (around 21 to 26 degrees Celsius)—so visitors can enjoy them even in winter.
Cuzamá is technically reachable by a 1.5-hour bus journey that departs from the Noreste terminal in Mérida, but travel by car is recommended. The cenotes are open daily from 8:00 a.m. to 5:00 p.m.; the last cart leaves the departure point at 3:30 p.m. Early arrival is recommended for those who don’t wish to share the water with others. The price for a ride on the cart, which carries four people, is posted various internet resources as 300 pesos, but recent experience found it to have been raised to 400 pesos. Note that only natural sunscreen and bug repellent is allowed in the cenotes. Plastic bags for cell phones and cameras are recommended.
Cuzama Cenotes. Near the small town of Cuzama, southeast of Merida are three lovely cenotes. Cenotes are large freshwater sinkholes part of the world’s largest underground river system. They are former caverns whose roofs have caved in and are sacred to the Mayans. Occasionally several hundreds of meters deep, their water is unbelievably clear and with amazing stalactite and stalagmite formations making them a favourite for divers and snorkelling.
Half the fun of these particular cenotes is getting to them on small railway trolleys pulled by horses on rickety, crooked, and narrow (2’) rail lines. If you meet another car, one of them must unload and hoist the car off the tracks to let the other pass. One visits three cenotes over rails running for nine km.
three completely separate cenote complexes around Cuzama run by three entirely different cooperatives: X’Tohil, Cuzama, and Chunkanán. It is very easy to get them confused with one another. All three Cuzama cenote cooperatives provide similar experiences with a horse-pulled cart ride, yet they simply visit different cenotes. Competition is fierce and you’ll experience people flagging you in as you approach. (X’Tohil).
Chunkanán, as it is $100-pesos less than the other two.
Cuzama cenotes as it gives you the most time being pulled around on the carts.
X’Tohil, as it’s most convenient to reach by bus or colectivo from Merida.
Chunkanán cenotes of Cuzama.
The first is large and has hundreds of bats wheeling around the cavern.
The last goes down a steep ladder through a tiny hole. I went for a wonderful swim in the warm water.
#1 path to the first Cuzama cenote. It was a beautiful underground cenote walked us over to what looked like a small hole in the ground. old homemade wooden ladder that vertically down into the pitch black, beyond what I could see. So we proceeded to climb down, found another ladder and continued climbing down into this Cuzama cenote until we reached a pool of water
It was, in fact, the second Cuzama cenote!
There’s no place to stand. You go directly from ladder to water. To our surprise, once we got to the bottom of the ladder, the underground cenote was beautifully lit. There was a light connected to a generator, which was strung by long extension cords to the surface.
back onto the cart. third Cuzama cenote. This was probably the most scenic of the three Cuzama cenotes and it had a nice deck to sit on or jump off.
Loltun Caves. The largest caves in Yucatan, human presence in the caves has been dated to 9000 BC. With huge caverns, Mayan carvings and 2 large rooms filled with trees, the caves were a good stop. My drive here started at the Mayapan Mayan ruins, I drove through two towns with no signs (Oxkutzcab had wonderful murals above its market) and several one-lane roads and finally arrived at the caves,
KOOTENAY MOUNTAINEERING CLUB HIKING CAMPS
Limestone Lakes, Height of the Rockies Provincial Park. The Kootenay Mountaineering Club had hiking camps here in 1987 and 2009. The outstanding features of the area were Island Lake, a large ultra-marine blue lake flanked by 10,000-foot peaks, stratified cliff faces, and huge fossil beds. It was easy to recognize shells and corals especially brain coral.
The 2009 camp was just west of Height of the Rockies Provincial Park. Amazing fossil beds and karst features were the highlight. We hiked on long game trails, the legacy of many mountain sheep.
Karst has sharp edges that make for interesting walking, Climbing is a challenge with the sharp edges to the rock.
Mt Llewellyn, Northern Selkirks. The KMC had a hiking camp here in 2005. The area was 25 km east of Revelstoke, BC. The rock here was limestone creating “disappearing” creeks. One creek came mysteriously out of the side of a mountain. Another creek disappeared underground and reappeared several hundred metres downstream. Mt Kenneth and Llewellyn were technical climbs and not climbed.
KOOTENAY MOUNTAINEERING CLUB HIKING CAMPS
Limestone Lakes, Height of the Rockies Provincial Park. The Kootenay Mountaineering Club had hiking camps here in 1987 and 2009. The outstanding features of the area were Island Lake, a large ultra-marine blue lake flanked by 10,000-foot peaks, stratified cliff faces, and huge fossil beds. It was easy to recognize shells and corals especially brain coral.
The 2009 camp was just west of Height of the Rockies Provincial Park. Amazing fossil beds and karst features were the highlight. We hiked on long game trails, the legacy of many mountain sheep.
Karst has sharp edges that make for interesting walking, Climbing is a challenge with the sharp edges to the rock.
Mt Llewellyn, Northern Selkirks. The KMC had a hiking camp here in 2005. The area was 25 km east of Revelstoke, BC. The rock here was limestone creating “disappearing” creeks. One creek came mysteriously out of the side of a mountain. Another creek disappeared underground and reappeared several hundred metres downstream. Mt Kenneth and Llewellyn were technical climbs and not climbed.