Ain Murr - An active Geo-Hydrotherm in the Sudanese part of the Jebel Uweinat
 (three countries corner Egypt/Sudan/Libya)

Norbert Brügge, Germany


The Jebel Uweinat is a sandstone plateau in the Western Desert that rises on the edge of a large granitic intrusion of tertiary ages up to 1200 m above ground. The plateau of Paleozoic sandstones is located directly above the uplifted Archean Basement of the ESGC. The expanded region is characterized by a multitude of volcanic structures that were created in the Tertär period. In the meantime, there are growing indications that post-volcanic activities could have existed up to the recent past (Holocene). The Jebel Uweinat provides sufficient discussion material for this.
At the moment, a possibly even a recent post-volcanic activity in the Jebel Uweinat is coming into focus. Andras Zboray ( has also explored a dry valley in the southeastern part of the Uweinat during his numerous tours. His informations and photos are of great interest because they allow an extraordinary interpretation of the spring "Ain Murr"as a geo-hydrotherm.
This dry valley, called Karkur Murr, is known to connoisseurs due to its palm grove, temporary water holes and further up in the valley the constantly water-bearing spring "Ain Murr".
From a geomorhological point of view, this part of the Karkur Murr can be described as an erosion channel, in which the sandstone layers have been eroded down to near base of the crystalline surface,which is to be expected here at about +700 m asl.

Thanks to the information provided by Andras Zboray, the following is known in summary about the spring "Ain Murr" and the following waterholes downstream:
  • The spring "Ain Murr"carries water permanently. In a valuable water analysis from 2002, a conspicuous concentration of Ca-Na-Mg sulphates was found.
  • The ground between spring and a striking water hole, 90m downstream, is covered with a thin crust of white crust of anhydrit crystals.
  • But there are more water holes with residues of crusts down the valley including at the palm grove, about 400m down the valley.
  • Currently at the striking water hole are to see adhering crystals on reed, which suggests a higher water level.
  • The edge of the spring is mostly free of crystals as the rivulets and water holes itself, probably due to the solution of crystals by weakly contaminated water.
  • However, there are permanent markings of white crust on the rock directly above the spring, which indicate high water levels from up to 40/50 cm above normal level.
  • The water holes are supplied with leachate from the spring with normal level conditions and if not they dry out.
  • About 150m in upstream of the spring crossing a fault the valley. In this area, some palm trees and fresh grass grow on the damp ground. A connection with the spring is suspected.

  Hydrological Research Institute in Budapest




Specific conductivity



Chemical oxygen absorbtion



Total hardness



Total dissolved matter







































Hypothesis of a hydrogeological scenario, derived from informations and photos

The following hydrogeological model can be developed based on for years documented conditions around the spring "Ain Murr" spring and water holes (see history):

The spring "Ain Murr" has an unhindered underground hydraulic connection to a hidden hydrotherm, which is located about 150m upstream at a striking west-east fault. In the area of the suspected geo-hydrotherm there is vegetation (some palm trees and grass) and at least a moist soil. The spring "Ain Murr" down the valley is the end point of a reservoir of hydrothermal water, which collects in a morphological deepening of the basement and is filled by the hydrotherm.
The geo-hydrotherm has short eruptive phases at intervals, as a result of which highly sulphate-rich water emerges at the "Ain Murr" spring. Then there is a violent outflow of water above the ground, which flows down the valley.
 After the hydrothermal water has cooled, the first sulfate crystals form downstream when the water level is still high (crystals in the reeds or on stone surfaces). In the course of the event, the water output at the spring decreases again. Water that remained in the bumps between the spring and the water holes then evaporate and leaving a crust of anhydrite.
The white crust largely persists because it cannot be dissolved by further events with highly concentrated water.
If there are no crusts on the edge of the spring itself and in the residual water in the rivulets, there will have been solution effects due to the already lower concentrated water after an eruption has subsided. This also applies to the pools in the water holes after an eruption.
On closer examination, however, it can also be ascertained that white crusts can very well have been preserved at the edge of the spring. There are also permanent markings at the "big rock" above the spring. That are bands of crusts and rust-colored strips that document different water levels of up to 50cm above normal and that clearly prove eruptive overflows of the spring.
the period between the eruptions, depending on the normal water level of the spring, the water holes can be weakly filled with leachate from the spring.
The normal water level fluctuates around 10cm. When it reaches its peak, water seeps away in the direction of the water holes. Depending on the surface of the terrain, they fall dry one after the other when the water level drops and there is no seepage. If the water level rises slightly again, the opposite effect occurs.
This water from the spring is contaminated with differently low sulfate concentrations. This is supported by differences in the taste perception of the leachate in the water holes (water exchange).
A special feature are darker, partially eroded deposits at the "big rock" on the spring and in the downstream. Rust-red and yellow-red deposits can be seen in exposed areas. It will be older deposits and therefore prove a long lasting lifetime of the geo-hydrotherm (Holocene). Such deposits can prove that "Ain Murr" was a formerly more active hot Sulphur source.

Note: Andras Zboray does not agree with my hypothesis of an violent overflow the spring "Ain Murr". Further research is planned for March 2021 at the earliest. Above all, the obvious presence of further deposits up the valley must be checked.


Suspected Hydrotherm

It is believed that the "Ain Murr" spring is just a stagnation point of water that is supplied underground by a hydrotherm. About 150 m upstream there is a west-east fault, which is crossed by the Karkur Murr. In both the main and secondary valley, palm trees and grass grow on a soil that isoccasionally at least moist.



2006: Palms

2006: Fresh grass

2015: Palms (3)

Crystalline underground
An outcrop of the crystalline underground in the valley is up to now not detected. It could be the suspected Archean Basement. Thanks to Andras Zboray, there are photos and a sample from an elevation in the valley, nearby the palm grove, which according to initial findings is a trachyte like intrusion.

Numerous bright clusters can be seen in a sample in a slightly brownish-colored groundmass. Enlarged, these clusters contain directed elongated white crystals. The entire matrix contains small reflective crystals. A few small gas bubbles are visible. If it is trachyte, the elongated crystals are alkali-feldspar. Andras Zboray: A hardness and acid test exclude a amount of quartz or carbonate in the rock.

History of discovering
(visited and documented by Andras Zboray nine times from 2002 to 2019)

2019, March
The documented white deposits directly at the spring are convincing for a recent overflow of the spring. They are located on the surface of stones and also as
parallel markings on the "big rock" itself. It is visible that the height of an eruptively water levels was more than 40-50cm above the normal water level. Fresh crusts and crystals can be found in the filled water holes in the downstream.



Residual water from the spring's last overflow



Spring downstream

Fresh crust near palm grove

Fresh crystals on  trachyte outcrop nearby the palm grove

Quote: "We found the spring of Ain Murr with abundant water, both at the main source and along the series of shallow pools below."
"Vegetation like in 2015. Pools were full, including those near the palm grove far downstream from spring. Lot of fresh vegetation farther upstream in valley at the fault."

2015, November
The vegetation at the source is clearly disturbed. Currently, the water holes have already dried out due to a low water level. A defect line filled with crystals on the "big rock", far above the normal water level, is visible again.




Spring downstream


Quote: "The vegetation around the spring of Ain Murr was much less than on previous visits, the secondary serie of holes were all dry. The spring itself was almost completely overgrown with vegetation, showing only a small patch of open water."

2010, March
The fresh crusts in the entire downstream and the holes filled with water are a clear sign that there was a recent "eruption" of the spring.


Striking pool

Crystals in the reed



Nearby palm grove

Fresh crystals

 Artificial holes

Quote: "There was much more water as 2009, the shallow pools between the two springs all had some water or at least wet mud on their bottoms, and the cluster of reeds a short distance south of the main spring were actually standing in water. We also observed a strange transformation of the water. While the upper larger spring was rather bitterish when we last visited in November 2009, the water taken from under the rock in the smaller pool some 200 metres away was crystal clear, and practically tasteless. Now the striking pool also was as bitter, or even more than the upper spring, which appeared to have cleared somewhat."
"The first series of shallow pools had mostly dry reeds, but there was shallow water in them. Second series of pools among rocks lower down all had water."

2009, November
A recent event is undetectable. The upper water holes are already dry. The deposits of crystals from eruptive water levels can be recognized by the "big rock". The white crust on the upstream side of the "big rock" (even with the splashes) is also not new either.


Splashes by the flank

Spring area


Striking pool

Artificial hole
Quote: "Only in a small hole under a rock a hundred metres below the spring was water. While the water in the spring was murky and tasted the usual bitterish, the small hole had crystal clear and almost tasteless water. Aside this hole, there was no trace of any water in other holes, only the thick white dry salt crust."
"The spring was overgrown with vegetation. The first series of shallow pools had mix of dry and still green reeds, but the pools dry. Second series of pools among rocks lower down had pool with water under a large rock."

2006, October
Little or no seepage from the spring. The water holes were almost all dry.



Water in a artificial hole

Quote: "Still plenty of green grass and green reeds, but no water in the shallow pools. There was water in the artificial hole at the second series of pools lower down."

2005, October
There is no evidence of a recent event. The markings on the "big rock" are not new. The higher water lines with white crystals are shown in the photo.

Spring area







Striking pool

Quote: "The vegetation around the spring was much less than on previous visits, the secondary holes were all dry. The spring itself under the big rock was almost completely overgrown with vegetation, showing only a small patch of open water. Abundant green grass in watercourse and green reeds in pools, but no observable surface water."

2004, October

Holes before Palm grove (2002)


Hole with very little water

Quote: "Don’t have any photos, don’t remember if there was any water in the pools. Visited the lower spring (Ain Brins), it had very little water."

2004, March
Photos document a recent "eruption" at the spring following activation of the Hydrotherm. The soil in the immediate vicinity of the spring is still damp. The water holes in the downstream are filled. For the first time, eroded remains of an apparently older gray deposit were documented, which was deposited at the source itself and in the downstream. It contains rust-red and red-yellow deposits, as can be expected from a "Hot Sulphur Spring".



Older deposits



Spring area downstream

Spring area upstream

Hole downstream

Striking pool

Palm grove area

Quote: "It was interesting to note, that in 2004 water was seeping out from cracks in a distinct rock band for about 200 metres along the wadi, forming numerous little pools. The water seemed more abundant then when we last visited in October 2002. The first series of shallow pools had green reeds and water. There was open water at the second series of pools lower down. There was a trickle of water among the rocks above the palm groves."

2002, October
The soil at the spring should not document an overflow of the spring. Since the first water hole with the reeds has already dried up, an event would have happened some time ago. Traces of higher water lines with white crust on the "big rock" are not visible in the photo, but there are probably old rust-red strips from running back water at the upstream side. The devastation at the spring could have been caused by humans. The barriers with brushwood are unnatural.



Striking pool

Quote: "The first series of shallow pools had mix of dry and stll green reeds, but the pools dry. Second series of pools among rocks lower down had a clearly excavated pool with water