An awesome view awaits.
The Dhofar Mountains are riddled with caves. Its limestone rocks are deeply cut by wadis draining north into the desert and southwards across the coastal plain into the sea.
A typical karst country, with ridges and hollows from millimetre to hundreds of metre scale formed by the dissolution of limestone rock. The same dissolution can create huge caves in the limestones below. Collapsed caves or large dissolution holes form what is known as sinkholes or dolines. In many cases they will be filled with sediments. Flat rounded features in a limestone country are the telltale signs of dolines hiding below.
The limestones of the Dhofar mountains feature great examples of such sinkholes such as Tawi Atayr and the great Taiq Sinkhole. You will notice that there is a very flat rounded area next to the Taiq sinkhole, clearly another doline and once your eye will get tuned in Google Earth you will spot many more. The rocks in the Dhofar Mountains may hide many more caves or extensive cave systems still to be found and explored.
Typical karst surface with dissolution ridges and hollows.
It is not merely another sinkhole; it is a rather big one.
The elliptical hole has a width of approximately 1000metres in SSE-NNW direction and 750metres in NNE-SSW direction. The deepest point is approximately 750m from the top lip. The highest point along the rim is at ±1000m altitude (southern and eastern sides). With an average height of approximately 975m of the rocks surrounding the hole and an average height of some 800m inside, the total volume amounts to a whopping 90 million m3. Compare this to the Tawi Atayr sinkhole with a diameter of some 80metres and a depth of 200m and a volume of 'only' 1 million m3, or the largest cave in Oman, the Majilis Al Jinn, which has a volume of about 5 million m3 and you get a feeling of the sheer size of this enormous hole.
Origin
Limestone, with its high calcium carbonate content, is easily dissolved in the acids produced by organic materials. About 10% of the earth's land surface consists of soluble limestone, which can be easily dissolved by the weak solution of carbonic acid found in underground water. When limestone interacts with underground water, the water dissolves the limestone to form karst topography - an amalgamation of caves, underground channels, and a rough and bumpy ground surface. Karst topography is named for the Kras plateau region of eastern Italy and western Slovenia (Kras is Karst in German for "barren land"). The underground water of karst topography carves our impressive channels and caves that are susceptible to collapse from the surface. When enough limestone is eroded from underground, a sinkhole (also called a doline) may develop. Sinkholes are depressions that form when a portion of the lithosphere below is eroded away. Sinkholes can range in size from a few feet or meters to over 100 meters (300 feet) deep. They've been known to "swallow" cars, homes, businesses, and other structures. A sinkhole can even collapse through the roof of an underground cavern and form what's known as a collapse sinkhole, which can become a portal into a deep underground cavern. While there are caverns located around the world, not all have been explored. Many still elude spelunkers as there is no opening to the cave from the earth's surface.
One theory of how doline/sinkhole can form.
Illustration of how this sinkhole could have formed by the collapse of an underlying cave system. The partial overhanging to vertical walls of the sinkhole support this hypothesis. Just west of the sinkhole is a round area with a perfect flat surface, which could hide yet another sinkhole, or doline to use the scientific name of these features. An check on Google Earth reveals quite a number of possible dolines, suggesting many and possible large cave system hiding in the limestones below.
Thank you and acknowledgments to: http://home.kpn.nl/~janm_schreurs/Tayq.htm
Logging requirements
In order to substantiate your visit and be able to claim this Earthcache, a number of questions need to be answered and submitted to the cache developer, via e-mail.
You could also post a photograph on the site with your log of you or your team and GPSr standing near GZ. There are stunning views here and it would be an absolute shame to come here without a camera to preserve your memories. [Optional]
1. Describe your trip from the coast to the cache location. Particularly mention the points of geological and geographic interest (rock formations, rivers, gorges, other sinkholes, plataues etc.).
2. Describe some of the shapes of the Taiq sinkhole – look particularly at the bottom surface and see if you feel there is ANY evidence for caves below to substantiate the formation of the sinkhole according to the theory/picture in the cache description.
3. Take a small piece of the limestone rock with you (you will not need more than about a thumb sized piece). Take it back to your home/hotel/base camp. Put it into a glass (preferably a transparent vessel0 and cover it with a vinegar solution. Describe what happens.
4. Please note and post photographs of any other interesting things you saw at this cache or in the area. I look forward to alol the interesting logs. You are welcome to add this to your cache log too.
NOTE: You may log your visit prior to approval, but e-mail submissions that do not meet the above criteria will be deleted.
