Exploration of Desert Caves in Central Saudi Arabia

by John J. Pint and Mahmoud A. Al-Shanti

The earliest explorers of Saudi Arabia’s desert caves were the local people, whose daily lives represented a struggle for survival in a very harsh environment. For them, the caves promised a possible respite from heat, cold, and the wind-blown sand. Oftentimes, a brackish pool, hidden at the bottom of a deep pit, was their only source of water.

Modern cave explorers crawl into the 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 limb and life 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.

The photographs 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 that were 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.

The cavers requested permission to explore these cavities from the emir of Ma’aqala, who assigned a knowledgeable old-timer to guide the visitors to the caves. He led them to a hard-pan area, filled with holes and within walking distance to the red sand dunes of the Dahna. They explored these cavities methodically, frequently finding all the horizontal passages blocked by sand, with no sign of the decorative 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 feet feeling for each rung of the cable ladder swinging to and fro in the darkness. They descended into a bell-shaped room that led 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 to unexpected directions. They realized that Saudi Arabia has limestone caves of great sizes, beauty, and complexity, and their enthusiasm knew no bounds.

As more and more remarkable caves were located, word reached the scientific community, inspiring geologists, biologists, and hydrologists to investigate. Following these early explorations, John J. Pint joined the Saudi Geological Survey (SGS) and an SGS subproject was established to explore and examine the caves in the Umm er Radhuma and elsewhere, in a systematic manner. No matter what remains to be discovered, however, the early cavers will not forget the wonderful sights that met them when they first succeeded in entering Dahl Sultan.

 

Desert Caves in Central Saudi Arabia

Exploration of Desert Caves in Central Saudi Arabia
by John J. Pint and Mahmoud A. Al-Shanti

 

 

Geology of the Caves of Central Saudi Arabia

by Peter R. Johnson

This is a collection of photographs of a group of underground caves around the town of Ma’aqla, 200-250 km NNE of Ar Riyadh, in a region that is quite flat, 400-450 m above sea level. The caves are located in the desert, but were formed by the action of rain and running water.

 

 

WHAT ARE CAVES?

Caves are air-filled underground voids, developed by the former action of water on a rock that over long period of time was dissolved and opened 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 the limestones, 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 formed 50 million years ago from the calcareous shells and skeletons of countless organism 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 the Rus formations (see map). 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 the 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 sulfuric acid rises from deep below the surface, but this is rare. It is not known if any of the caves here have formed in this fashion. Most likely, they all formed by the action of water, either by falling rain or by streams that sink into the ground through the 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 and dissolves the limestone bedrock, forming cavities and interconnected 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 acidic water would enter the limestone where the streams sink down the holes and cavities. The underground water will move along the bedding and the joints, forming long tunnels through combined solution and normal erosion. Sometimes, the water moves very slowly and dissolves the rock instead or 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 about caves is due to the wonderful and varied types of deposits that form inside the caves after the water table drops and begins 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 climates, surface processes, fauna, and flora. Careful chemical analysis of the cave deposits reveals information about the abundances of the different isotopes of carbon, sulfur, and other trace elements that were present in the atmosphere, when the deposits formed, and gives the age of the deposits. These two types of information, chemical and chronologic, provide a record of climate change. Examination of the bones, pollens, and spores that may be trapped in the dusts and silts in the caves, gives information about the types of animals and plants that existed in the recent past in the 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 the increases and decreases of rainfall.

 

Curiously shaped stalactites may remind the observer of flowers or animals

 

Slow crawlway will sometimes lead to spectacular formations hundreds of thousands
of years old

 

Dahl Sultan is a labyrinth of underground passages, many of which still await exploration

 

In many parts of Dahl Sultan, visitors can stroll through spacious passageways like this one

 

In Saudi Arabia, speleologists can park their cars directly in front of a cave entrance, making it easy to anchor their ropes

 

A stalagmite is formed by drops of water containing calcium carbonate. The process can take hundreds of thousands of years

 

Strategic placement of lanterns brings a warm glow to the Show Room in the Friendly Cave

 

Friendly Cave could become a tourist attraction, where visitors can admire its beautiful formations without getting close enough to damage them

 

Resembling plants or frosted feathers, these calcite formations decorate the ceiling deep inside the cave

 

A natural dome occurs halfway along the Camel Aisle. The nearby walls are covered with a thin lacy layer of calcite

 

The first room in the Dahl Murubbeh is fifty meters long and is home to owls, foxes, and rock doves

 

A human skull lies among the bones and horns of a wide variety of animals. Carbon dating suggests these bones are about 1,000 years old

 

Unperturbed by the mosquitoes and sand flies that are sometimes found in the Mossy Cave, this visitor admires a flowstone display

 

The delicate formations of this cave will be preserved only, if visitors are careful not to touch them

 

The water is crystal clear, but the flip of a fin can resuspend the fine, anhydrite silt, reducing visibility to zero

 

Delicate and beautiful crystals, such as these, have been broken off and removed from several caves in the Summan Plateau

 

Angled “duck tails” suggest that the coating on the stalactites may have been deposited by supersaturated air

 

Some cave formations are reminiscent of the coral bushes found in the Red Sea

 

The Scorpion’s Tail is a very delicate, segmented formation of calcite crystals

 

Small nooks and crannies of the cave may be filled with long, delicate gypsum needles

 

The doorway to the passages that are still unexplored. Less than 600 meters of tunnels have been mapped in this cave

 

Suspended above a sheer drop of 70 meters, the cave explorer’s life depends on a single rope

 

On the floor of the cave, directly under the entrance, lies a steep hill of sand and rocks, created by the collapse of the roof

 

This gecko proved to be the ideal photographer’s model, posing patiently for over an hour and even allowing itself to be moved from place to place on the stalactite

 

It will take more than a gecko guard to protect the formations of this cave, all of which are within easy reach of a visitor

 

Trident bats (Asellia tridens) live in several of the caves and eat harmful insects, like sand flies. These bats can fly to as far as 50 kilometers in a single night

 

It’s not a tall tale to say that in the Summan karst you can’t walk for a minute without coming to a dahl

 

Helpful hands hold a caver who is attempting to extract a rock, which is blocking the entrance to the Dahl Iftakh

 

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Curiously shaped stalactites may remind the observer of flowers or animals.

Slow crawlway will sometimes lead to spectacular formations hundreds of thousands of years old.

Dahl Sultan is a labyrinth of underground passages, many of which still await exploration.

In many parts of Dahl Sultan, visitors can stroll through spacious passageways like this one.

In Saudi Arabia, speleologists can park their cars directly in front of a cave entrance, making it easy to anchor their ropes.

A stalagmite is formed by drops of water containing calcium carbonate. The process can take hundreds of thousands of years.

Strategic placement of lanterns brings a warm glow to the Show Room in the Friendly Cave.

Friendly Cave could become a tourist attraction, where visitors can admire its beautiful formations without getting close enough to damage them.

Resembling plants or frosted feathers, these calcite formations decorate the ceiling deep inside the cave.

A natural dome occurs halfway along the Camel Aisle. The nearby walls are covered with a thin lacy layer of calcite.

The first room in the Dahl Murubbeh is fifty meters long and is home to owls, foxes, and rock doves.

A human skull lies among the bones and horns of a wide variety of animals. Carbon dating suggests these bones are about 1,000 years old.

Unperturbed by the mosquitoes and sand flies that are sometimes found in the Mossy Cave, this visitor admires a flowstone display.

The delicate formations of this cave will be preserved only, if visitors are careful not to touch them.

The water is crystal clear, but the flip of a fin can resuspend the fine, anhydrite silt, reducing visibility to zero.

Delicate and beautiful crystals, such as these, have been broken off and removed from several caves in the Summan Plateau.

Angled “duck tails” suggest that the coating on the stalactites may have been deposited by supersaturated air.

Some cave formations are reminiscent of the coral bushes found in the Red Sea.

The Scorpion’s Tail is a very delicate, segmented formation of calcite crystals.

Small nooks and crannies of the cave may be filled with long, delicate gypsum needles.

The doorway to the passages that are still unexplored. Less than 600 meters of tunnels have been mapped in this cave.

Suspended above a sheer drop of 70 meters, the cave explorer’s life depends on a single rope.

On the floor of the cave, directly under the entrance, lies a steep hill of sand and rocks, created by the collapse of the roof.

This gecko proved to be the ideal photographer’s model, posing patiently for over an hour and even allowing itself to be moved from place to place on the stalactite.

It will take more than a gecko guard to protect the formations of this cave, all of which are within easy reach of a visitor.

Trident bats (Asellia tridens) live in several of the caves and eat harmful insects, like sand flies. These bats can fly to as far as 50 kilometers in a single night.

It’s not a tall tale to say that in the Summan karst you can’t walk for a minute without coming to a dahl.

Helpful hands hold a caver who is attempting to extract a rock, which is blocking the entrance to the Dahl Iftakh.

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From the book:

Pint, J.J., and Al-Shanti, M.A., 2001. Exploration of desert caves in central Saudi Arabia, With discussion of the geology of Saudi Arabian caves by Johnson, P.R.: Saudi Arabia Geological Survey Data File Report SGS-DF-2001-1, Jeddah, Saudi Arabia, 54p.