Sabkha is an Arabic name for a salt-flat that has come into general use in sedimentology following classic research in the United Arab Emirates of the Arabian Gulf in the 1960s and later. A supratidal part of a large coastal sabkha at Umm Said in Qatar. This particular area is the remains of a lagoon indirectly filled with siliciclastic sand of aeolian origin, originating from some large barchan sand dunes. The flatness is controlled by the content of capillary moisture from the water-table, which is only about half a metre (one and a half feet) down, keeping the sand damp and firm and preventing it from being blown away. Any higher dryer sand can be moved away by deflation. This particular sabkha has much granular gypsum in addition to the sand.
They often appear to be ideal for driving over being wide and flat but their appearance is deceptive. They are composed of areas of saline sand or silt, lying just above the water table and generally deposited over a long period of time by the action of wind-blown sand falling into areas of low sea. Their flatness is controlled by the humidity associated with the presence of the relatively high water table which, commonly, is about half a metre below the surface. DO NOT ATTEMPT TO DRIVE TO GROUND ZERO! Park your vehicle at the edge and walk to ground zero. The location is easily reached with a saloon car but caution should be exercised at all times.
One of the features associated with sabkha is the presence of gypsum crystals formed within the sabkha. These appear as two crystalline forms. The first takes the shape of fans of needle-like gypsum sand and appear where the stronger structures are exposed as the lighter sands are moved away from them. These tend to be found in the area south of Umm Said towards what is known as the Inland Sea.
The second form have the appearance of agglomerated shells and are familiarly known to English speakers as ‘desert roses’. They tend to be found in low areas in the north, east and central part of Qatar. They are delicate and can be easily broken or affected by water. There is no standard shape of these agglomerates, and they tend to be found in any numbers of crystals usually with just a part of them exposed. Those who dig to find them may go to a metre or so in order to uncover them. Obviously they are extremely sensitive to weathering and mechanical damage.
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 at cincolcc(at)gmail.com You can also post a photograph on the site with your log of you or your team and GPSr standing on the sabkha.
1. Describe in your own words what the crust of the sabkha looks like to the naked eye.
2. Describe in your own words what the crust of the sabkha feels like when you rub it between your fingers.
3. Briefly describe what the texture feels like underfoot on your way to Ground Zero.
4. Why would it be dangerous to drive over this sabkha?
NOTE: You may log your visit prior to approval, but e-mail submissions that do not meet the above criteria will be deleted.
