On a hot, sunny day in March 1999, we set out for our usual weekend of cave exploration among the sinkholes between the villages of Ma’aqala and Shawyah, 200 km north of Riyadh. We knew there had to be several unknown caves under the surface, waiting to be discovered. The Bedouins have known about the sinkholes for centuries as a potential source of water, but it is only recently that a more systematic exploration of them has been undertaken. After some time we found a hole that looked very interesting. After rigging up the gear and ropes for descending I lowered myself through the little opening.
At the bottom, the shaft narrowed and I had to squeeze myself through the last meters of limestone rock. And then, I was standing upright on a sandy floor, looking at a wide tunnel with no end and full of beautiful stalactites. I named it Surprise Cave. It turned out to be the most beautiful cave in the area. How did I become involved in this?
Well, you could say it started 200 million years ago. The plateau, named As Sulb, was then submerged under a vast sea, which covered much of Saudi Arabia. The sea was full of marine life, many of them with shells made up of lime. During millions of years, the creatures slowly sank to the bottom, and a mighty layer of limestone formed. Eventually, the land rose from the sea, and the limestone formation was exposed. The process of cave formation then went through different stages:
Rain falling through the atmosphere picked up enough carbon dioxide to become slightly acidic. This weak acid ate away the rock at a rate of roughly 10 mm per 1000 years, creating cavities that were filled with water from the surface. In the alternating dry periods when the water table fell, the caverns were air-filled. Stalactites were now slowly formed by dripping water. Between 1.6 million to 700,000 years ago a warm, rainy period prevailed which transformed Arabia into a lush savannah. It was probably during this time that the greatest amount of dissolution of the area took place.
A lot of holes in the ground opened up when the roofs of the caverns closest to the surface gradually collapsed. During the last 6000 years, all of northeastern Saudi Arabia has stayed dry and the caves have mostly remained dry, while the water table has fallen progressively
In 1983, John Pint, an English teacher, stumbled upon a 20-year-old Aramco map showing an unusual concentration of sinkholes, known locally as dahls, around Ma’aqala. In 1986 a joint team from King Fahd University of Petroleum and Minerals and the Austrian Academy of Science scientifically explored and mapped an area of 500 sq km containing 58 dahls between the villages of Shawyah and Ma’aqala.
Four 4 km north of Shawyah is the UPM Cave, named after the University of Petroleum and Minerals in Dhahran. The biggest chamber, the Dabbagh Hall, measures 45 x 80 meters and is 17 meters high!
It is a magnificent sight when you enter the big hall after passing the last tunnel. Here was once a big underground lake. The cave does not contain many stalactites but has a lot of pretty formations known as gypsum flowers. One of the most interesting caves is Dahl Shawyah, which has two entrances, the biggest one leading to a marvelous domed cavern and a side tunnel with exquisite gypsum hair. Perhaps the most interesting part is a small entrance to the right of the main entrance where there is a colony of leaf-nosed trident bats. While other caves in the area are humid and hot, typically 26-28°C, Dahl Shawyah is cool and dry, providing a perfect environment for preserving remains carried into the cave by predators many centuries ago. About 1000 years ago, a pack of striped hyenas lived here, and we have found lots of remains of camels, donkeys, hedgehogs, gazelles, and also two human skulls. One of the first caves I visited, Mossy Cave, had one cavern full of stalactites.
That cave also taught me an important lesson in cave safety. I could not find my way out! For some reason, I became disorientated and returned to the same place over and over again. Finally, I had to give up and wait in the dark for the people on the surface to start looking.
‘Since then we have always used a thin but strong white rope to mark our way. At New Year 1998 I found a cave that I called Friendly Cave. The formations here are very impressive and concentrated in one room, the Showroom. It is almost like being in a sacred shrine in caves of this kind.
Carbon dating of the formations in the upper part of the cave revealed that it was over 47,000 years old. Although deposit formations – known as cave decorations – are generally uncommon in Saudi Arabia’s caves, those at Ma’aqala have them in great abundance.
Caves like Friendly Cave, Surprise Cave, and Mossy Cave all contain stalactites, drip curtains, gypsum flowers, and selenite crystals. Stalagmites are not commonly seen, however, except in Surprise Cave, which we discovered in March 1999. This large cave contains numerous beautiful decorations. And as water continues to drip from the roof, the cave is still evolving.