The large cliff face in front of you is often referred to in tourist literature as “the Travertine Curtain”. However it is more technically correct to refer to this as TUFA. Tufa is precipitated as water containing dissolved carbonate minerals. As the water is aerated it deposits the carbonates. Tufa is sometimes referred to as (meteogene) travertine; care must be taken when searching through literature to prevent confusion with hot spring (thermogene) travertine. This is the more common association for the word travertine. Also note that tufa should not be confused with tuff, a porous volcanic rock with parallel etymological origins.
At the start of the hike
Tufa in this form (sometimes refferred to as Waterfall Tufa) is deposited mainly at large knick points (or dramatic changes in angle) such as a waterfall. Here the water with the high degree of calcium carbonate dissolved becomes supersaturated as the speed of the water, the aeration and the pressure change (lower pressure as water is exposed) lead to an micro environment where deposition can occur of the calcite out of te water onto the surrounding surface. It is also postulated that moss and algal growth on the surface of these waterfalls aids in the entrapment and provides some stability for the travertine to deposit out and harden with time. This particular travertine (tufa) rock surface covers a large cross section (often reffered to as Oman's Niagra Falls) where the wadi Darbat and it's reservoir above falls over the escarpment and deposits the travertine out. Judging by the current semi-arid climate, this is more likely to be an indicator of a far moister time period of the region's history, although, as typical of karst areas (as indicated by the many sinkholes and limestone outcrops) water does contain a higher than normal calcium content.
Do visit the nearby Tawi Atayr EarthCache and make sure you climb down to the required waypoint. Also make a diversion to the top of this cliff and get a close up look of the wadi above.
Sample photo at Travertine Curtain
For additional background and historical interest - those purists of EarthCaches can stop reading here ;) - I include below an excerpt from one of the first recorded accounts of this area by a westerner. Theodore Bent and his wife Mabel more than 100 years ago gave a description that can't be improved, capturing very much the feeling of the wadi as it still is despite modern road and cars. Let's start their story from Taqah where they first explored Khor Rori. Traveling with the local people they heard stories as were told at that time. This provides quite a bit more background than more recent tourist guides:
".....Leaving the harbour behind us we again approached the mountains, and, after journeying inland for about eight miles, we found the valley leading up to the mountains choked up by a most remarkable formation caused by the calcareous deposit of ages from a series of streams which precipitate themselves over a stupendous wall in feathery waterfalls. This abyss is perfectly sheer, and hung in fantastic confusion with stalactites. At its middle it is 550 feet in depth, and its greatest length is about a mile. It is quite one of the most magnificent natural phenomena I have ever seen, and suggestive of comparison with the calcareous deposits in New Zealand and Yellowstone Park; and to those who visited this harbour in ancient days it must have been a familiar object, so no wonder that when they went home and talked about it, the town near it was called the City of the Abyss, and Ptolemy, as was his wont, gave the spot a fresh appellative, just as he called the capital the Oracle of Artemis....."
About a quarter of a mile from the western side of the whole abyss is a small conical mountain, about 1,000 feet high, which looks as if it had once stood free but were now nearly smothered by the petrifaction of the overflowing water. It rises above the level top of the cliffs, and has about a quarter of a mile of abyss on one side, which is only 300 feet in depth, and half a mile on the other. It is all wooded. The larger side and the upper plain is called Derbat, and the smaller Merbat or Mergà. The three days we spent in exploring the neighbourhood of this abyss were the brightest and pleasantest of all during this expedition. Our camp was pitched under shady trees about half a mile from the foot of the abyss, whither we could wander and repose under the shade of enormous plantains which grew around the watercourse, and listen to the splashing of the stream as it was precipitated over the rock to irrigate the ground below, where the Bedouin had nice little gardens in which the vegetation was profuse. One day we spent in photography and sketching, wandering about the foot of the rocky wall; and another day, starting early in the morning, with one camel to carry our things, we set off to climb the hill by a tortuous path under shady trees which conducted us along the side of the hill, and got lovely glimpses of the abyss on both sides through the branches.
On reaching the summit we found ourselves on an extensive and well-timbered flat meadow, along which we walked for a mile or so. It was covered with cattle belonging to the Bedouin grazing on its rich pasturage. It seemed like the place Jack reached when he had climbed up the beanstalk. At length we came to two lovely narrow lakes, joined together by a rapid meandering stream, delicious spots to look upon, with well-wooded hills on either side, and a wealth of timber in every direction. We lunched and took our midday siesta under a wide-spreading sycamore by the stream, after walking up alongside the lakes for nearly two miles; fat milch cows, not unlike our own, were feeding by the rushing stream; birds of all descriptions filled the branches of the trees, water-hens and herons and ducks were in abundance on one of the lakes, bulrushes and water-weeds grew in them; it would be an ideal little spot in any country, but in Arabia it was a marvel. The trees were loaded with climbing cactus and a large purple convolvulus with great round leaves. We wanted to get some water-plants, easily to be obtained if anyone would have entered the lake in which they grew, but the jinni or ghinni who lives there (our old friend the Genius of the 'Arabian Nights') was so dangerous that the plants had to be hooked out with sticks and branches tied to strings. Sheikh Sehel maintains that he has seen ghinni in that neighbourhood. This wide-spreading meadow can be watered at will by damming up the streams which lead the water from the lakes to the abyss, and in a large cave near the edge of the precipice dwells a family of pastoral Bedouin who own this happy valley; before leaving the higher level we went to the edge and peered over into the hollow below, where, far beneath us, was our camping ground among the trees, and in the sun's rays the waterfall over the white cliff gave out beautiful rainbows. We had to cross much swampy ground, and got our feet wet, without catching the inevitable fever. Imam Sharif camped away from us one night and found that the streams which feed them have their source up in the limestone, about two days' journey from them. The Bedouin are exceedingly proud of them, and in the absence of much water in their country they naturally look upon them with almost superstitious awe and veneration. Perhaps in Scotland one might be more inclined to call them mountain tarns, for neither of them is more than a mile in length, and in parts they are very narrow; yet they are deep, and, as the people at Al Hafa proudly told us, you could float thereon any steamer you liked, which may or may not be true, but their existence in a country like Arabia is, after all, their chief cause for renown. This really is Arabia Felix. (Ref: Bent, T. & M., 1900, Southern Arabia. Smith Elder & Co., London)
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 must also post a photograph on the site with your log of you or your team and GPSr standing near GZ (see example photo above). [optional]
1. Describe the “travertine curtain” in your own words. Mention in particular any “unusual” features on the curtain that caught your attention.
2. Explain how you believe this feature formed. Compare this to how stalactites form underground. Do you see any similarity?
3. Estimate the height and width of the curtain.
4. What is the Khareef?
NOTE: You may log your visit prior to approval, but e-mail submissions that do not meet the above criteria will be deleted.