3N Cave, New World’s Longest Cave in Salt
During the last January 2006 expedition the Big Ponor Cave was connected with the Cave of Tøí Naháèù (former second longest cave in salt). The resulting cave was named 3N Cave and altogether with newly mapped parts reaches the total length of 6,580 m. It is some 900 m longer than Malham Cave (5,685 m, Mt. Sedom, Israel) now being the second.
3N Cave, New World’s Longest Cave in Salt
M. Filippi(1), Z. Vilhelm(2), J. Bruthans(2), M. Zare(3) and N. Asadi(3)
(1) Institute of Geology, Academy of Science of the Czech Republic, Rozvojová 269, 165 02 Prague 6, Czech Republic, e-mail: firstname.lastname@example.org
(2) Department of Hydrogeology, Engineering Geology and Applied Geophysics, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic, e-mail: email@example.com
(3) Department of Earth Sciences, Faculty of Sciences, Shiraz University, Shiraz, Iran
Key words: salt karst, 3N Cave, longest salt cave, Iran
Abstract: During the last January 2006 expedition the Big Ponor Cave was connected with the Cave of Tøí Naháèù (former second longest cave in salt). The resulting cave was named 3N Cave and altogether with newly mapped parts reaches the total length of 6,580 m. It is some 900 m longer than Malham Cave (5,685 m, Mt. Sedom, Israel) now being the second.
Between 1997 and 2006, we carried out six expeditions and two shorter trips to a salt karst in the south and southwestern part of the Zagros Mountains (Iran). The research of salt karst has been jointly held by Charles University in Prague, Shiraz University and Czech Academy of Sciences.
Rock-salt is rising from underground in a form of cylindrical bodies of salt diapirs. Rain water corrodes the salt and creates an extensive karst features including numerous caves (Bosák et al., 1998, 1999; Bruthans et al., 2000, 2003). The Holocene depositional history and uplift rates of two most studied diapirs and some notes to speleogenesis will be published soon (Bruthans et al., in print).
Up to date, we mapped 19 salt caves with a total length of 14.1 km on Namakdan, Hormoz, Kuh-e Jahani and Kuh-e Khurgu diapirs. Several tens of other caves were located and sketched.
Studied salt karst is a geologically active and rapidly changing environment. Especially during and after rains, several risks exist: First, all the surface karst features of the salt diapirs formed in a sedimentary cover (cap-rock) relatively weekly cemented by gypsum, that undergoes a distinct dissolution by rain water. Then, intense land-sliding and collapsing of ravine walls occurs. Second, the caves are modelled by flood-waters, therefore they become partially or completely flooded and some places change to sumps. Plus, due to a rapid corrosion of rock-salt, frequent collapsing of cave ceiling especially in ponor parts of the caves takes place.
3N Cave (6,580 m)
The 3N Cave and related Upper Entrance Cave are developed in the SE part of Namakdan Salt Diapir in western part of Qeshm Island (Figure 1). The 3N Cave consists of one large meandering passage opened by entrance (8 by 2 m) in the western wall of outlet valley (Fig. 2). This lower entrance is partly filled by brine. Another large lake, 300 m long and up to one metre deep was developed at 160 m from the entrance behind small collapse dam between 1999-2004. The lake was dry in spring 2005, as well as this year, as the dam had been washed out by flood. Abundant curved stalagmites were typical, hanging above the lakes. At about 700 m from the entrance, the “Hangar” hall is developed (35 by 20 by 16 m). Behind this point, the passage width decreases from 10 - 15 m to only 6 m. One kilometre from the entrance, several domes (up to 40 by 20 by 15 m in size) created by ceiling break down occur. Around that place, there are three shafts connecting the cave with the surface; all about 40 m high. These can be used as an alternative entrance to the cave, but there is a trouble with anchoring, as the salt is fragile and corrosive and the unstable sediments on the surface under the cave give only small possibility for making stabilization points for the ropes.
Upstream to the shafts the draught dies out and the character of the passage changes: The arched spaces modelled by breakdown that occur below the shafts turns into a very wide spaces with almost flat ceiling without any traces of collapsing. The first harder crawlway “Bend” is about 150 m long. The passage becomes larger and larger further on. On the right side, there is a permanent shower of brine called “Waterfall”. This 10 m high vertical chimney was climbed in 2006 using an aluminium ladder. 170 m long minor meandering passage was mapped in the upper level. The passage continues, but the spaces are very narrow and frequent fractures and fallen blocks from the ceiling indicate increased danger of collapsing.
On the left side of the main corridor, there is an older level, so called “Snow Passage”. The main corridor reaches the width of 40 m and height up to 6 m here (“Namakdan Highway”). Suddenly the large corridor turns right and quickly decreases clearing to only half a metre. The most challenging – more than 500 m long – “Azadi´s Crawlway” starts here. Fortunately the crawlway was bypassed in 2004 by a shortcut “Motashakkeram” we dug through an older +6 m level, so now one could safely reach the upstream parts of the cave in case that some flooding occurs. Either way one gets to “Megadomes”. These are two extensive, but relatively low halls – together they occupy an area of 200 by 100 by 2-8 m. They are situated at a confluence of streams from two main ponors of this cave. Further upstream one can take a fossil corridor named "Old Passage" or another crawlway "Active Passage" with an active channel, wide but of a very low clearing. The latter was connected to Big Ponor Cave this year.
The Big Ponor entrance is situated in a deep ravine with extremely unstable sides. An ephemeral stream drains a flat plateau of eastern Namakdan disappears in a huge portal (35 by 15 m) below some 100 metres of a hanging wall. After a large entrance hall (ca 50 by 50 by 15 m) there are several low passages in different directions. They became inaccessibly low after several tens of meters due to a coarse gravel fill. In January 2006 we dug through the fill and found several hundred metres of new passages and finally also the way to Cave of Tøí Naháèù. The new spaces are generally very low, filled by sand and coarse gravel to cobbles. Especially after a major precipitation event, the whole Big Ponor part might be very dangerous. First, because of collapsing of the ceiling and second, there is a place marked “Sandy Sump” on the map, that becomes filled by water and sediments during flooding (it was impassable in 2004). There are a number of other shorter passages going in various directions wedging out because of a sedimentary filling.
Upper Entrance Cave (length 650 m)
The Upper Entrance Cave is probably connected to the 3N Cave though the connection was not confirmed yet. Cave entrance is developed in a blind end of a ravine, similar but smaller to that leading in the Big Ponor Cave. The cave begins with a labyrinth of very low passages that have joint flat roof of rock-salt, bottom and sides are built by coarse cobbles, gravel and sand. Some 60 m from the entrance, a large corridor starts. Unfortunately, this larger corridor mapped during previous expeditions was not accessible in January 2006 because of a plug of sediments. The distance from the end of mapped passages to the 3N Cave is only about 130 m. As the water can apparently pass through, there is a chance that the inner parts of the Upper Entrance Cave will open again in future.
Many thanks to all staff of Department of Earth Sciences of Shiraz University for a great support in the field. We would like to thank Mr. Dareshouri, from Qeshm Free Zone Organization for his support during the field works in Qeshm Island. Special thanks to Martin Sluka for lending us his equipment for cave mapping. Research was supported by project no. B301110501 of the Grant Agency of the Academy of Sciences of the Czech Republic. The authors thanks also to Ceskomoravsky Cement Co. (Heidelberg Cement Group) for financial support.
- Bosák P., Jaroš J., Spudil J., Sulovský P., Václavek V. (1998): Salt Plugs in the Eastern Zagros, Iran: Results of Regional Geological Reconnaissance. – GeoLines, 7, 1-174. Inst. Geol. Acad. Sci. Cz. Rep. Prague
- Bosák P., Bruthans J., Filippi M., Svoboda T., Šmíd J. (1999): Karst and Caves in the Salt Diapirs, SE Zagros Mts., Iran. – Acta Carsologica, 28/2, 41-74
- Bruthans J., Šmíd J., Filippi M., Zeman O. (2000): Thickness of cap rock and other important factors affecting morphogenesis of salt karst. – Acta Carsologica, 29/2, 51-64
- Bruthans J., Filippi M., Šmíd J., Palatinus P. (2003): Tøí Naháèù and Ghár-e Daneshyu Caves: The world´s second and fifth longest salt caves. – International caver 2002, 27-36
- Bruthans J., Filippi M., Geršl M., Zare M., Melková J., Pazdur A., Bosák P. (in print): Holocene marine terraces on two salt diapirs in Persian Gulf (Iran): age, depositional history and uplift rates. – Journal of Quaternary Science