Bait al Afreet or better Bimmah Sinkhole EarthCache
Bait al Afreet or better Bimmah Sinkhole
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Bimmah sinkhole is one of the world’s natural oddities. Geologists say this 40 meter wide, 20 meter deep water-hole was created when a limestone cavern collapsed, but the locals say a piece of the moon fell from the sky and made the hole and call the sinkhole as "Bait al Afreet" - "House of the Demon"...
Hidden features that you do not see:
The Bimah sinkhole is a spectacular limestone crater and is filled with water. There is an underwater tunnel leading to the sea 500 metres away. So, this sinkhole was formed naturally when the ground over unstable layers collapsed on itself. To reach the water, climb down the stairs is required. The top layer of the water is crystal clear and in winter the temperature was about 25 degrees. The middle part of the sinkhole is shallow and there are some green algae growing at the deeper areas. On the opposite of the stairs the water get deeper and diameter of the hole increases with depth. The wall becomes a roof on which algae and small sponges grow. Up to around 8-meter depth the water is clear but deeper the water becomes very warm and gets a orange brown color with a sulfuric taste. Sulfur-oxidizing bacteria colored the orange water. The sulfuric acid produced by bacteria is hollowing out the lime stone hole and would showing a PH of 4-6 in water samples. Both the muddy bottom and stone roof lay under a slope of around 30 degrees. The visibility in 15-meter depth is less then 1/2 meter. Most deeper it becomes very disorientating. The space between the wall/roof and bottom slope is maybe 4 or 5 meters and hitting the roof could be painful. On left side from the stairs there is an underwater cave going about 10 meters inside the limestone. The maximum depth here is about 8 meters and the water is crystal clear. Disturb the sediment will reduce the visibility to very low levels.
Formation:
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Many millions of years ago:
Underground water from the mountains, flow into the
ocean. Now, water penetrate the rock layers and the
upper layers of the soil begin to erode.
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The mechanisms of formation involve natural processes
of erosion or gradual removal of slightly soluble bedrock
(such as limestone here) by percolating water, the
collapse of a cave roof, or a lowering of the water table.
Sinkholes often form through the process of suffosion.
Thus, for example, groundwater may dissolve the
carbonate cement holding the sandstone particles together
and then carry away the lax particles, gradually
forming a void.
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Some tens or hundreds years ago:
This geological formation, thousands of years later the
ground over unstable layers collapsed on itself and
formed naturally the unique limestone crater.
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To log this cache, send me an email with the answer of my Questions.
1st: Describe the form and color of surface texture inside the crater.
(You will find 2 different surface-forms)
2nd: What could be the reason for this? Describe in your own words.
3rd: Estimated the dimension "x" of the limestone layer (see picture.).
4th: You´ve learned there is an underwater tunnel leading to the sea 500 metres away.
Taste (NOT drink) the water with your tongue. Is the water salty?
Optional: "It would be nice you could take a picture with you and the sinkhole in the background"
Please send your answers to the following address: strahle_man@web.de. Please write your GC-Nickname in subject heading.
You may log the earthcache without my permission. If i find any incorrectness, i will write an email to you.
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