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Sunday, August 11, 2013

New to nature no 111: Typhleotris mararybe

A species of cave fish discovered in Madagascar commemorates the fever caught by the people who discovered it.
Typhlerotris mararybe View larger picture
A cave fish with a difference: Typhlerotris mararybe. Photograph: John S Sparks
Most of the 150 or so types of cave fish pale in comparison to a newly discovered species from an isolated karst sinkhole in south-western Madagascar. Fish living in perpetual darkness typically share a syndrome of convergent features, including the loss of eyes and pigmentation accompanied by enhanced non-visual sensory structures on the head. The new species, Typhleotris mararybe, is small, about 38mm, and combines dark pigmentation with an absence of eyes and well-developed sensory canals and pores on its head. Its body is uniformly brown in colour, as are the basal one-third of its caudal, pelvic, pectoral and anal fins, whose extremities are without pigment and white.
Cave fishes have been known to exist in Madagascar for a century, but the extent of the fauna and details of their biology, relationships and distributions remain largely unstudied. While the four cave-inhabiting fishes from the island nation are all gobioids, they represent two separate evolutionary lineages.
First is a single species of the Gobiidae genus, Glossogobius, whose other species are found in Africa and Indonesia. Second is the genus Typhleotris of the family Milyeringidae, all three species of which are endemic to Madagascar.
John S Sparks, of the American Museum of Natural History, and Prosanta Chakrabarty, of Louisiana State University, described the new species, giving it a name with a unique derivation. The specific epithet is from the Malagasy words "marary", meaning ill or sick, and "be", meaning big.
The resulting name, mararybe (or "big sickness"), commemorates a strange and debilitating viral "sinkhole fever" that members of the field team suffered after diving in Grotte de Vitane. The Grotte de Vitane sinkhole is on the arid coastal plain below and west of the Mahafaly plateau in south-western Madagascar, near the town of Itampolo, and is a challenging place to collect. The two specimens of the new species collected by the senior author are a tribute to his resolve. After descending to the water by way of a chain ladder, it took four hours swimming and snorkelling to capture them with a handheld net. Both were caught at a depth of no more than 1.5 metres.
The sinkhole is a sacred site visited by locals who come to offer prayers. Interestingly, while locals were aware of other Malagasy cave-inhabiting fish before their discovery by scientists, T mararybe was unknown to them, even though they sometimes descend to the water climbing down tree roots.
The authors make a compelling case that the new species evolved from an ancestral species that was both blind and unpigmented and that pigmentation has been secondarily regained. The sinkhole is part of a vast and unmapped system of subterranean waterways, explaining the arrival of an ancestor. The dark pigmentation of the new species is correlated with the direct sunlight that portions of the sinkhole receive and perhaps make the fish more difficult to see. T mararybe is a rather slow swimmer, like the other two species in the genus, although it was observed to move away from approaching objects more energetically than the related species T madagascariensis and to escape by diving.
There is evidence that T madagascariensis and T mararybe are sister species, sharing a number of fin and scale characters that aren't shared by a third species, T pauliani. Both morphology and molecular data point to a relationship between Typhleotris and an Australian genus, Milyeringa, that occurs in very similar habitats. The available geographic and geologic evidence associated with the fish are intriguing. While much of the coastal plain is younger Quaternary sandstone, the genus is so far restricted to older limestone karst of the Eocene age.
The two previously known species of the genus are both red listed by the IUCN as endangered. T pauliani is found in caves and sinkholes to the north of the Onilahy river drainage, while T madagascariensis is found to its south in the Mahafaly plateau and in isolated caves, sinkholes and wells on the coastal plain to the west. Given the single locality of the new species, it is almost certainly endangered as well. It would not be surprising to find additional species of the genus, but many sinkholes are accessible only to very experienced cavers and are located in remote and hostile environments, often a day or more's travel by ox cart from the nearest village.

Tuesday, August 06, 2013

Geological History in the Depths of Belize’s Great Blue Hole
  • Creole and Garifuna cultures bring bright colors, mouthwatering cuisine, and a contagiously easygoing attitude to the tiny Central American nation of Belize. But venture beyond the more tourist-trafficked beach towns, and you’ll experience a whole other Belize, one profound, mysterious, and intimately connected to nature.
    Out on the remote cayes of Lighthouse Reef Atoll, ecosystems both above and below sea level have remained largely unchanged for hundreds of years. And the main attraction for scuba divers is a veritable geological wonder: the famous Great Blue Hole.
    Great Blue Hole, Belize
    From above, this renowned dive spot looks like a dark blue circle in the middle of a vast expanse of turquoise. An aerial view awakens you to an oft-forgotten aspect of the ocean: its mind-boggling depth. The most frequently quoted ocean statistic is the fact that water covers 75% of Earth’s surface. Impressive, yes, but this stat nonetheless discounts the depth. Gazing down at the Great Blue Hole, it hits you. This blue-black void plunges into the heart of the ocean.
    Divers seek this limestone sinkhole for a challenge and a thrill, but also for an education in natural history. The Great Blue Hole’s geological past spans 150,000 years, back to a time when it actually existed above ground, as evinced by the presence of stalactites in its underwater caves. Although many mysteries remain as to the origins of the Great Blue Hole, scientists believe that a series of dry caves predating the Ice Age gave rise to the submerged sinkhole of today. Sometime before the last great thaw, an earthquake shook the area to an angle of 12 degrees, which explains why the stalactites hang so strangely tilted.
    Following this seismic upset, the melting of the last Ice Age flooded the cave systems and eventually the limestone ceilings of the once-dry caves collapsed under the weight of the water, creating one giant sinkhole 1,000 feet in diameter and over 400 feet deep. It’s a true geological oddity, appearing in stark contrast to the surrounding waters, which are so shallow that the coral peeks out of the sea at low tide.
    Underwater explorers who are not yet ready to attempt the Great Blue Hole often visit the coral that circumscribes it for some of the world’s best snorkeling and diving. A plethora of plants and animals inhabit the reef; lobsters, turtles, and schools of bright fish swim and feed in patches of the purple coral found around the Great Blue Hole, while the hole itself harbors virtually no marine life. Occasionally, a Caribbean reef shark or barracuda will pass through its upper regions, but the best sights within the Great Blue Hole are architectural. The magnificent structure of this underwater cave evokes an hourglass. A sheer limestone wall drops 50 feet to an overhang that supports enormous stalactite rock formations, then down to depths even expert divers cannot safely reach.
    Dive Belize
    Photo by helseike on Flickr
    Local myths maintain that the Great Blue Hole is bottomless, while other legends claim it holds terrifying sea monsters. These likely originated with the ancient Maya, who viewed sinkholes as sacred entryways to the underworld. In 1972, Jacques Cousteau descended to the very bottom in his research vessel, The Calypso, shedding light and fame on the deepest mysteries of the Great Blue Hole. He declared it one of the top ten scuba diving sites in the world. There have been rumors that Cousteau used dynamite to blast through part of the coral around the Great Blue Hole in order to navigate his boat, but these are fairly unsubstantiated, although Cousteau has admitted to employing explosives in other areas of Belize.
    In the years following Cousteau’s exploration, the Belizean government established the site as a National Monument and UNESCO designated it a World Heritage Site, ensuring its preservation for generations to come. Dive trips to the Great Blue Hole are usually day-long events, and often include dives in the nearby reef and a visit to the idyllic, isolated Half-Moon Caye. The eco-resort on Zophora promises to all but eliminate travel time to the Great Blue Hole while accommodating adventurous divers in sustainable luxury on Long Caye, located just 15 minutes from this geological wonder.

Monday, August 05, 2013


Cenotes of the Yucatán is a route through the Yucatán Peninsula of Mexico. It follows a network of secondary roads through the interior of the peninsula which the Mexican government has dubbed La Ruta de los Cenotes (The Route of the Cenotes).


The underground river systems of the Yucatan flow beneath the entire peninsula. During the ice ages when the ocean levels were much lower than they are today, what was once a giant coral reef became exposed to the atmosphere and eventually became the Yucatan Peninsula. Massive cave systems were formed by gradual dissolving of the highly porous coral limestone. These caves are called "solution caves" because they were formed by the slightly acidic rainfall dissolving the alkaline limestone. Inside the caves the geological formations such as stalactites and stalagmites are a spectacular sight to see. Many of the caverns eventually collapsed and the sea levels rose partially or completely flooding the cave systems. The water table of the entire peninsula is filled with consists of seawater at sea level and freshwater 'floating' on top at varying depth depending on the distance from the sea. For instance, Cenote Zaci in Valladolid in the central Yucatan area is about 35 metres from ground level to the surface of the freshwater and probably another 30 metres below that would be the top of the saltwater layer.

It has been estimated that there are approximately 30,000 cenotes or exposed access points to these cavern and cave systems and thousands of miles of underwater cave passageways have already been explored and exploration continues in too many systems to count. Two of these cave systems have over 140 km of explored passages.

Cenotes are complexes of sinkholes and caves in the Karst geological landscape of the Yucatán. Some cenotes contain spectacular cave formations, while others are important archaeological sites, and several were considered sacred by the Mayans. A few are open to the public for swimming and diving. Of the estimated 30,000 cenotes, many of them unexplored, many are considered to be Mayan cultural and archaeological sites. Ancient fossilized remains of Camels, giant Jaguars and Mammoths are among the interesting archaeological finds in recent years. Most of these have been found by cave divers exploring underwater cave systems and some sites are now protected by INAH, the Mexican government archaeological and historical protection organisation.

Tour operators emphasize the sensitive nature of cenotes, and La Ruta de los Cenotes was first promoted as an ecotourism attraction that would offer sustainable development for the region. To promoters in Quintana Roo, it was a way to bring tourist revenue to a relatively forgotten and marginalized part of the Mayan Riviera. However, some Mexican environmentalists have criticized the construction of the eastern segment of the highway, both for the destruction of pristine forest lands and for the use of heavy equipment in sensitive areas.

Recently, experienced divers have discovered Maya artifacts upsteam of some of the sinkholes they explored dating back over 1,000 years. This has led them to conclude that the water table in this area was significantly lower at one time and the Maya inhabited the caverns which are now full of water. They also concluded that some of the sacrifices made, were to ask the spirits to lower the water table so that they could resume life in the caverns. They also believed that the Maya remained in the area for some time living above ground, while waiting on the waters to recede, before moving on.

Sunday, August 04, 2013

Cave Exploration in Saudi Arabia

Cave Exploration in Saudi Arabia
The Saudi Geological Survey has had an interest in the study of caves and lava tubes since 1999, when a foreign caving expert was first hired by SGS and a team of Saudi geologists was built who could systematically investigate underground cavities in the Kingdom. In part, the interest in Saudi caves has coincided with a Kingdom-wide interest in developing sites of geo-touristic potential; but as part of its scientific mandate, SGS has an interest in caves because they may contain a detailed record of past climate, surface processes, and be sources of data that can be used in studies of climate change.
SGS interest in caves resulted in the publication, in 2003, of a hard-back volume called The Desert Caves of Saudi Arabia, which is available for purchase from SGS. The balance of this section of the SGS website consists of excerpts from this SGS title, which focused on underground caves around the town of Ma’aqala, some 200-250 km north-northeast of Riyadh. Those who want more information about Saudi caves might also connect to the website which is the independent website of the SGS cavers.

The earliest explorers of Saudi Arabia's desert caves were bedouins, whose daily lives represented a never-ending struggle for survival in one of the harshest environments on earth. For them, the caves promised a possible respite from heat, cold, and howling sandstorms. Many times, a brackish pool hidden at the bottom of a deep pit was their only source of water.
Modern cave explorers crawl into dark voids beneath the sands for other reasons. Some are attracted by the strange and often breathtaking environment totally unlike the stark desert above. Others are taken by the sheer challenge of risking life and limb on a thin nylon rope to penetrate an inky-black world where one small mistake can result in death. All of these explorers relish the possibility of reaching large caverns where no human being has been before.

For the most part, the photographs in this site represent cave exploration in Saudi Arabia during the last twenty years. This activity was triggered by a study of old maps showing a great number of natural water wells clustered around a small settlement named Ma'aqala, located just east of the Dahna desert atop a great bed of limestone and dolomite known as the Umm-Er-Radhuma formation.

Cavers requested permission to explore these cavities from the Emir of Ma'aqala who assigned a knowledgeable old-timer to guide the visitors to thc caves. He led them to a hard-pan area filled with holes, within walking distance of the red sand dunes of the Dahna. These cavities they explored methodically, frequently finding all the horizontal passages blocked by sand, with no sign of the limestone formations they had hoped to see.

The situation seemed less than encouraging until the day they came upon a small hole no wider than a dinner plate. Warm, humid air was blowing from this hole so strongly that it seemed worth the effort to enlarge it with a chisel.
When the opening was finally big enough to admit a human visitor the cavers squeezed into the hole, their unseen feet feeling for each rung of the cable ladder swinging to and fro in the darkness. They descended into a bell-shaped room which led them to a labyrinth of horizontal passages. Here they found stalactites, stalagmites, columns and other calcite and gypsum formations of great beauty and variety. Every time they thought they had reached the end of the cave, which they named Dahl Sultan, they found new passages leading in unexpected directions. They realized that Saudi Arabia has limestone caves of great size, beauty and complexity and their enthusiasm knew no bounds.
What are Caves?
Caves are airfilled underground voids developed by the former action of water on rock that over a long period of time was dissolved, opening up holes and tunnels in the ground. The holes and tunnels in cave systems are normally interconnected, depending on how the water seeped through the rock along joints and cracks, working its way down to the water table below the surface of the ground.
 The caves illustrated here are in limestone - the most common type of rock to have caves - which in this part of Saudi Arabia consists of calcium carbonate and small amounts of magnesium carbonate. The rocks found  50 million years ago from the calcareous shells and skeletons of countless organisms that flourished in shallow warm seas that covered the Arabian Peninsula. Over time, the shelly deposits were cemented by additional calcium carbonate, became hard and turned into limestone, forming a geologic unit referred to as the Umm er Radhuma and Rus Formations. Starting 25 million years ago, these formations were raised above sea level by earth movements affecting the whole of the Middle East, and were exposed to wind and rain at the surface.
The action of water percolating down through soluble rock is critical for the formation of most caves. Some caves develop because sulphuric acid rises from deep below the surface, but this is rare and it is not known if any of the caves in the Ma'aqala area formed in this fashion. Most likely they all formed by water action - either by falling rain or by streams that sink into the ground through joints and holes.

The process of forming caves in soluble rock is very slow. As rain falls through the air, it absorbs a small amount of carbon dioxide and picks up additional carbon dioxide from the soil. The result is a weak solution of carbonic acid that seeps downward, dissolving the limestone bedrock and opening up cavities and inter-connected channels. If streams flow on the surface - and in the recent geologic past, Saudi Arabia was much wetter and probably had permanent drainage - additional weakly acid water would enter the limestone where streams sink down holes and cavities. The underground water will move along the bedding and down the joints, forming long tunnels by combined solution and normal erosion. Sometimes the water moves very slowly and dissolves the rock instead of wearing it away, creating an intricate labyrinth of passageways. In other places, joints become enlarged, resulting in vertical shafts and chimneys.

Cave Deposits
A large part of the fascination that people feel for caves is because of the wonderful varied types of deposits that form inside caves after the water table drops and they begin to dry out. This is because the water that drips into, or flows through the now air-filled cave, is still full of dissolved minerals that precipitate as the carbon dioxide escapes from the water. The results are cave deposits, or speleothems, as they are technically called, There are two main types: stalactites, which are formed by water dripping from the ceiling and hang from the cave roof and stalagmites, which grow up from the floor where the drops fall.

Some caves have beautiful coatings of minerals where thin sheets of water flow down the cave walls or along inclines. Others have small pebble-like deposits or cave pearls that grow in small pools.

The Importance of Caves
Caves are important, not only because they are beautiful and awe-inspiring, but because they provide a detailed record of past climate, surface processes, fauna, and flora.
Careful chemical analysis of the cave deposits reveals information about the abundances of different isotopes of carbon, sulphur, and other trace elements that were present in the atmosphere when the deposits formed and gives an age of the deposits. The two types of information - chemical and chronologic - provide a record of climate change.
Examination of bones, pollen, and spores that may be trapped in dust and silt in the caves gives information about the types of animals and plants that existed in the recent past in areas that are now desert.
Surveying the caves and mapping the types and distributions of cave deposits provides information about the rise and fall of the water table, which, in turn, is a key to understanding the changing rates of discharge and recharge of the water volume and increases and decreases of rainfall.

• Ain Hit: Diving in the Desert
• Dahls and  Survival in the Desert 
• Dharb Al Najem
• Gecko Gave
• Mossy Cave
• Surprise Cave
• The Discovery of Dahl Sultan
• The KFUPM – Austrian Expedition Project
• The Whistling Teapot
• Treasures of Dahl B-7/ Murubbeh
• UPM Cave

Ain Hit: Diving in the Desert
Southeast of Riyadh near AI Kharj lie several sinkholes that offer direct access to a vast aquifer lying deep below the surface.
The most famous of these holes is Ain Hit. where geologists, invited on a picnic by King AbduIaziz, discovered the first surface outcrop of anhydrite in the Kingdom. In recent years. experienced cave divers have carried their heavy equipment into Ain Hit down to the edge of a lake 120 meters below the surface. Using breathing equipment they began an exploration of this Dahl's submerged passages, which, they claimed contained the clearest  water they had ever seen anywhere in the world.

Writing of his visit to the northern Summan plateau in 1917-18, Philby describes natural shafts or dahls (duhul in Arabic) up to ten meters deep, where rain water tended to collect in pools. Aramco CEO Tom Barger, writing from Ma'aqala in 1939, reported:
'The water comes from dahls, sinkholes in the limestone that vary from a foot to 10 feet in diameter. The one with the most water has the dirtiest water; it is more thin mud than water. The 'biggest one requires crawling through 100 yards of winding tunnel and dragging the water out in gurbas [water-skins].' (Out in the Blue, Selwa Press, 2001)

Dharb al Najem
The name Dharb al Najem means' Place Where the Star Fell to Earth and suggests how local people may have thought this great hole was created. Located in the desert east of Majma'ah this cave consists of a single chamber roughly measuring 100 meters in depth by 100 meters in diameter. A person descending by rope into this huge room can only feel as small as a spider on a thread.
Upon arriving at the bottom, he or she is treated to the awe-inspiring sight of a bright shaft of sunlight cutting through the darkness and lighting up the wings of hundreds of rock doves soaring overhead.

Gecko Gave
This cave gets its name from the many geckos (Plyodactylus hasselquistii) that wander about its ceiling. These creatures are very beneficial to human beings because one or their favorite meats is the sand fly. Which carries the bacteria that causes leishmaniasis, a disease that has Ions plagued the inhabitants or the Summan plateau.
Much of Gecko Cave can only be visited on hands and knees, but the thick carpet of sand found throughout the cave makes this a peasant task. Visitors will find themselves surprised again and again by the beautiful and delicate formations decorating every room.

Mossy Cave
This cave was discovered by accident when a group of explorers took a shortcut in order to recover a lost flashlight. Bright green moss, which is not something one expects to find in a parched desert caught the cavers' eyes and led them to a baroque world of gaudy, crystalline draperies and tiny intricate tangles of helic¬tites. One of its most outstanding formations, a very long stalac¬tite called The Rope, was accidentally smashed not long after Mossy's discovery Visits to such caves should be limited to very small groups or responsible adults.
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Surprise Cave
Hundreds of dahls dot the karst lying east of the Dahna desert. Most of these are small and uninspiring but among them may be found the entrances to complex caverns of great beauty. Having spent all day checking dahl after dahl, cave explorers were about to give up when they decided to climb down one lest hole. Fifteen metres below. they found thick dust and broken rocks. It looked anything but promising but then they came to a few old-looking stalactites To their great surprise, this passage led them into one of the biggest and most beautiful caves ever found in Saudi Arabia.
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The Discovery of Dahl Sultan
In the early 1980s, cave explorers learned that a large number of pits or dahls were concentrated around a small settlement called Ma'aqala. located alongside the Dahna Desert. With the help of the Emir of Ma'aqala. a study of the area was begun. Many of the cave passages were found to be blocked by drifting sand but then a small hole was discovered /Tom which a strong current of warm, moist air was blowing The exploration of what may be the largest cave in Saudi Arabia was about to begin.

The KFUPM – Austrian Expedition Project
In 1986 the Summan Plateau karst was chosen for an important study by scientists from King Fahd University of Petroleum and Minerals and the Austrian Academy of Sciences, The focus was on the role that dahls play in replenishing the large aquifer that supplies potable water to much of Saudi Arabia. During the course of this project, these investigators explored studied and surveyed some 58 caves, amassing over 500 pages of documents and maps on this area of vital concern to Saudi Arabia's future.

The Whistling Teapot
While drinking tea with friendly local residents, cave explorers learned about a small hole- not far from their tent. The local residents said a strong current of air was blowing from the hole, a good indicator that the cave could be very large. The entrance turned our to be a tube so narrow that it was impossible to lift the knee in order to climb the- cable ladder  forcing explorers to develop a new technique for 'auto-extraction' from the hole. Although quite small, the Teapot is one of the most beautifully decorated caves in Saudi Arabia.
Treasures of Dahl B-7/ Murubbeh
Many of the caves on the As Sulb plateau are- warm and humid. but Dahl Murrubeh is dry and remains at a temperature of 16 degrees centigrade all through the year. This has provided the ideal ambient for preserving hundreds of bones carried into the cave by hyenas about a thousand years ago. Murubbeh also contains beautiful crystal formations not round in nearby caves. Because it has a walk-in entrance - and a large room with a sandy floor. it has become a popular picnic spot and is in need of protection.

UPM Cave
UPM Cave was one of the major discoveries made by speleologists from King Fahd University of Petroleum and Minerals and the Austrian Academy of Sciences. It has passages on three different levels and is impressive not only because of a huge hall (45 by 80 meters and 17 meters high) which once housed an underground lake, but also thanks to rhe delicate beauty of small formations such as tiny pools of cave pearls and an ever-growing rimstone dam. So far, speleothems of this sort have been found nowhere else in the Kingdom.
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In addition to the book Desert Caves of Saudi Arabia, the SGS has also issued a number of open-file and data-file reports on Saudi caves and lava tubes, which are available from the SGS.  For information on obtaining SGS publications contact  SGS at .


Diver deaths spawn rumors of underground waterway

by Mike Smith Daily Lobo
About 120 miles east of Albuquerque, on the eastern edge of the town of Santa Rosa, N.M., lies a tiny oval of blue water – a spring-fed sinkhole about 80 feet wide and 81 feet deep – known as the Blue Hole.
Sometime ago a group of scuba divers dove into the Blue Hole, eager to explore every nook and fissure of the smooth-walled sinkhole. After climbing out, they realized one of their divers had disappeared.
Six months later, the body of that diver finally surfaced, but not in Santa Rosa. It was discovered, the story claims, in Lake Michigan – more than a thousand miles away – naked, waterlogged and with much of its skin scuffed off, as if it had been pushed and scraped through miles of rocky tunnels.
If the story is true, one of the longest underground waterways in the world could lie directly beneath us. Perhaps the direct water route across the continent searched for by the explorers Lewis and Clark actually exists – underground. Andrea Sachs, in a Dec. 19, 2004, Washington Post article, wrote that there is a protective metal grate covering a spring that produces about 3,000 gallons of fresh water per minute on the Blue Hole’s limestone floor. And, she wrote, that grate also seals off an elaborate network of caves that twists southward 200 miles, down to Texas.
“I don’t think anyone knows just how extensive that system is,” said Si Minton, owner of New Mexico Scuba Center. “No one has ever explored the total cave system below Blue Hole.”
“The only maps (of the cave network) are apparently sketches made by rescue divers. There are reportedly some rooms below the sink, and it goes to 250 feet with a going passage beyond,” said Mike Poucher, cartographer for the National Speleological Society Cave Diving Section. “How far does it go? No one knows.”
Poucher said the grate blocking the cave system was installed in the early 1980s, after at least four divers died in the caves during the previous decade.
In March of 1976, the Albuquerque Journal reported two of these deaths, detailing how a group of 10 university students were diving in the Blue Hole one morning, how 21-year-old David Gregg and 22-year-old Mike Godard failed to resurface, and how it took the State Police multiple dives to recover their bodies. In 1979, two other divers got lost and died in the caves. Their bodies were recovered as well.
That the bodies of all who drowned in the Blue Hole’s caves were quickly accounted for suggests that the Lake Michigan story really is only rumor, as does the area’s geology.
The odds of there being a hydrologic connection to the Great Lakes from New Mexico are about as remote as finding a wormhole to transport you there across time and space,” said scientist Mike Spilde, UNM’s resident cave-geology expert.
“In other words, it just doesn’t exist. First, it would require a continuous rock stratum capable of supporting caves to be present all the way from New Mexico to the Great Lakes, which there isn’t. More importantly, the body would have to get past the huge hydrologic barrier of the Mississippi River. The river acts as a giant collection system, moving not only surface water to the ocean, but a lot of subsurface water, too. The body would have to swim upstream to get to the Great Lakes,” he said.
So, perhaps the story isn’t so strange after all.
However, in 1976 and 1979, as the young divers swam their ways silently through dark caves deep beneath the New Mexico desert, feeling the walls for a way back out, the truth of the story was probably strange to them. As they lost their way, their headlamps dimmed and died, their air supplies seeped away in panicked moments, and they swam from this life into the wide unknown that follows. The events of their mornings could not have felt entirely normal.
Me jumping into Blue Hole in 2007


Secrets of Yucatan Caves

Cave divers in Mexico’s Yucatan Peninsula area may have discovered the earliest evidence of humans in the Americas.  Exploration of these flooded caves is in it’s early stages since the openings are hidden deep within the dense jungle.  The geology of this area is primarily limestone that is easily dissolved with rainwater.  Approximately 12,000 years ago, at the end of the Pleistocene epoch the melting of the ice caps caused a dramatic rise in global sea levels, which flooded low lying coastal landscapes and cave systems. At the Aktun-Hu cave system in the state of Quintana Roo, divers reached the furthest extent of that… the pit.  The pit is approximately 200 feet deep and 120 feet in diameter and the bottom of it holds the mystery.  They first came across several megafauna remains and what was clearly a mastodon bone, and a human skull resting upside down with other nearby remains at about 140 feet.  The skull looks pre-Maya, which could make it one of the oldest set of human remains in the area.  Gaining an understanding of how this human and these animals entered the site will reveal an immense amount of knowledge from that time.  Dating of the skull is still being processed but it has potential to change history in the Americas.

Human skull discovery

Cave divers in Mexico’s Yucatan Peninsula area may have discovered the earliest evidence of humans in the Americas.  Exploration of these flooded caves is in it’s early stages since the openings are hidden deep within the dense jungle.  The geology of this area is primarily limestone that is easily dissolved with rainwater.  Approximately 12,000 years ago, at the end of the Pleistocene epoch the melting of the ice caps caused a dramatic rise in global sea levels, which flooded low lying coastal landscapes and cave systems. At the Aktun-Hu cave system in the state of Quintana Roo, divers reached the furthest extent of that… the pit.  The pit is approximately 200 feet deep and 120 feet in diameter and the bottom of it holds the mystery.  They first came across several megafauna remains and what was clearly a mastodon bone, and a human skull resting upside down with other nearby remains at about 140 feet.  The skull looks pre-Maya, which could make it one of the oldest set of human remains in the area.  Gaining an understanding of how this human and these animals entered the site will reveal an immense amount of knowledge from that time.  Dating of the skull is still being processed but it has potential to change history in the Americas.

Human skull discovery


2006 National Geographic Emerging Explorer Kenny Broad free dives into the eerie looking Devil's Ear in Florida. Broad and his filmmaking partner Wes Skiles encountered many dangers while making the movie "Extreme Cave Diving". (photo by Wes Skiles)
2006 National Geographic Emerging Explorer Kenny Broad free dives into the eerie looking Devil’s Ear in Florida. Broad, and his filmmaking partner Wes Skiles, encountered many dangers while making the movie “Extreme Cave Diving”. (photo by Wes Skiles)
Every week, embark with host Boyd Matson on an exploration of the latest discoveries and interviews with some of the most fascinating people on the planet, on National Geographic Weekend.
Please check listings near you to find the best way to listen to National Geographic Weekend, or pick your favorite segments and listen now below!
Episode: 1324 – Air Date: June 16
As National Geographic’s annual Explorer’s Symposium came to an end, we revisit some of our favorite adventures from the previous classes of Emerging Explorers. In the coming weeks and months, we will introduce the new class of Emerging Explorers on the show. Here are some of our favorites from over the years:
Caves are considered the most dangerous frontiers on the planet, and delving into their deepest crevices can be a monumental task. National Geographic grantee and 2006 Emerging Explorer Kenny Broad and National Geographic filmmaker Wes Skiles discuss the dangers they have encountered in their new NOVA/National Geographic documentary, Extreme Cave Diving.