Saudi Arabia’s Desert Caves

By John Pint
Photographed by Lars Bjurström

Lars Bjurström

Accessible only through rough and narrow passages, Mossy Cave’s ceilings “drip” with stalactites, which are deposits of crystallized limestone (calcite) left behind when mineral-bearing water drips from a gap in the ceiling.

More than 60 million years ago, a vast sea covered the lands that today are the central deserts of Saudia Arabia. Over eons, the shells and bones of the countless creatures that died sank to the ocean floor. In time, they hardened into the rock base that presently makes up the Arabian Peninsula’s Umm er Radhuma formation.

As the land continued to evolve, there were wet and dry times. In the wet periods, rain would sometimes pick up enough carbon dioxide from the atmosphere to become slightly acidic. When runoff flowed into the cracks in the rock base, this “acid rain” slowly ate away at the stone, leaving eroded patches. Over time, cavities formed, and more runoff from the surface filled them. Eventually, some of these cavities contained underground lakes and rivers. In dry periods, only a little water percolated down and underground water levels slowly dropped, allowing some cavities to fill with air. In these, one mineral-laden drop at a time, stalactites and stalagmites formed. Some have been dated to more than 270,000 years ago, while others are geological youngsters, only about 11,000 years old.

Throughout Saudi Arabia, the Umm er Radhuma region is known for its water holes. The formation’s vast body of rock holds water that percolated into it during the last wet period, some 18,000 to 30,000 years ago. Farther to the east, this fossil water actually gushes to the surface as springs and is then channeled to several modern agricultural projects.

Lars Bjurström

Above: Stalactites and stalagmites form as a result of calcium-laden water dripping through the ceiling of a cave and onto its floor. The water actually evaporates and what remains is the calcium. Stalactites build downward from the roof of a cave. When they fall to the floor and then build upward, they are known as stalagmites. Below: A caver in a chamber of “The Dome” in Dhal Shawyah.

As a cave explorer, I was intrigued by the gradually falling water table in areas with eroded rock. I wondered: Might some of these sinkholes—dahls in Arabic—lead to limestone caverns? In the early 1980’s, I began my search—accompanied by biologist David Peters and my wife Susana—in an area around Ma‘aqala, a small town several hours drive north from Saudi Arabia’s capital city of Riyadh. In the first holes we climbed down, the few horizontal passages we saw were filled with fine red sand, which had either blown or washed in. Then, one day, I chanced on a small hole that was no wider than a dinner plate. As I leaned over it, my face was suddenly bathed in a rush of warm air so humid that it fogged my glasses. Its strength suggested large chambers on the other side, and we were soon busy chipping away at the rather soft rock until it looked wide enough for us to fit through.

We did, but just barely. After squeezing through, one shoulder at a time, and feeling about for the rungs of our free-swinging cable ladder, we found ourselves in a bell-shaped room about 30 feet deep. On one side of the room, a jumble of large rocks had long ago fallen from the ceiling. Through these, we felt a current of air. So, on our bellies, we wriggled through an opening down into a low tunnel that branched off in two directions. As we cautiously made our way into chamber after chamber, we came upon majestic displays of sparkling mineral formations.

Although we found no water, it was clear that there had been water in the past. Some caves had deep grooves worn into the entrance lip by bucket-hauling ropes, a sure sign that the cave had dried out recently. The horizontal bands of color on the walls of some caves offered further evidence of past water. These were the result of interaction of water and air.

Locals told us that the dahls were thought to be home to jinn, spirits best left alone by humans. I was reminded of this belief when I squeezed down into one very tight hole. I was halfway down the cable ladder, swinging to and fro inside a large, almost round room, when I heard what sounded like a distant moan. I followed the sound, crawling through a small opening on my hands and knees into a long, low tunnel with smooth, almost white, walls and a floor of soft red sand. The farther I made my way into it, the louder the strange wailing grew and the more beautiful the passage became, until it seemed that every bit of the ceiling was covered with curling, ivory-colored cave deposits. It looked like an upside-down stage crowded with hundreds of beautiful, but out-of-step, ballerinas. In the last room was a sort of alcove and, in the wall above it, a small hole about three inches in diameter. Air was blowing furiously through it—a natural whistle.

I poked my smallest flashlight through the hole and looked over it into a bizarrely decorated room. I returned to the entrance room to report my find to my fellow cavers, but at the top of the cable ladder, I ran into a problem that many cavers have experienced. The ceiling was six feet thick, and once inside the tight tube leading up through the ceiling, I was no longer able to raise my knee to take another step up the ladder. Try as I might, I couldn’t advance! Fortunately, two Bedouin who had been watching our day’s expedition noticed my predicament. They reached down, grabbing the one arm above my head and pulling me out like a cork from a bottle. Eventually, we managed to tunnel through the soft sand under the wall of the “closet of the jinn,” but could go no farther.

As we worked our way back, we wondered how many more impressive pits there were to be uncovered, aware that the exploration of Saudi Arabia’s underground wonders is clearly just beginning.

Lars Bjurström (2)
Left: Interested spectators watch as a caver descends into a dahl, or sinkhole, in the limestone plateau near Ma‘aqala. Only a small percentage of dahls lead to dry caves. Most are plugged by windblown sand. Right: One of the largest and most complex caves in the Ma‘aqala area is UPM cave, named after King Fahd University of Petroleum and Minerals in Dhahran.

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John Pint is a member of the U.S. National Speleological Society, and with his wife, Susana, has explored and written about caves in Mexico and Saudi Arabia. He lives in Jiddah, where he teaches English and operates www.saudicaves.com

Lars Bjurström has lived in Riyadh for 11 years, where he practices dentistry and pursues his love of wildlife photography and caving. He has produced two films: "Travels in the Sand," about desert wildlife, and "Wonders under the Sand," about caves.