International Caving Expedition “Mount Sedom 2019”

Malham Cave Project – The Longest Salt Cave in The World

(22 February – 4 March 2019)

From 22 February to 4 March, an international team of cavers from Israel, Bulgaria, France, UK, Croatia, Romania and the Czech Republic explored and re-surveyed Malham cave, Mount Sedom, Dead Sea region, Israel.

As a result, we have the new longest salt cave in the world with about 10 km of multi-level stream galleries, 19 entrances (most of them are vertical shafts and the deepest one is -92 m).

Until this expedition, Malham cave was the second longest salt cave in the world with length of 5685m, resulting from two Israeli-Italian expeditions in the 80’s. The cave was originally discovered by the Israel Cave Research Center in 1981. This was followed by tens of research expeditions on the 1980’s exploring and surveying some 100 salt caves in the mountain. A first map of Malham cave was drawn in 1983-4 by two collaborative expeditions of the Israel Cave Research Center and Gruppo Grotte Milano SEM CAI from Italy. Since then, additional passages were discovered and surveyed by the Israeli team. Interestingly, within several decades, new passages have formed or enlarged enough to allow human passage, due to the high solubility of salt. The older, abandoned cave passages were dated to 7000 years by radiocarbon of wood twigs swept from the surface.

Тhe longest salt cave, before March 2019, was 3N (“Cave of three nudes” often abbreviated to 3N-cave, as the first explorers were naked during first exploration, as there is a large and deep salty lake at the entrance), located in Iran, with a length of 6580 m (map from 2006), result of several expeditions by Czech cavers.

The first international caving expedition, (in recent times) to the Malham cave took place from 11 to 22 January 2018. There were participants from Israel, Bulgaria, Czech Republic, UK, France and Germany – 11 from abroad and more than 20 from Israel. The main goal of the expedition was to resurvey the Malham cave, to create a new vector map and include the new passages that were found after the Israeli-Italian expeditions. During the survey, the teams re-mapped the known parts and found new passages. As a result: about 6 km were mapped by 4-7 mapping teams and 2-3 survey teams working both on the surface and in the cave, searching for abandoned channels and hidden passages. A later international expedition was planned for 2019.

Under the motto “Project: Malham – the longest salt cave in the world”, the 2019 expedition combined the efforts of the participants and led to the successful mapping of the longest salt cave in the world.

Final processing of the data from the mapping in order to have compete electronic map of the cave is in progress by the Bulgarian team. Then, the exact cave details from both expeditions in 2018 and in 2019, such as length and depth of Malham cave, will be published together with a completed map.

The expedition was organized by the Israel Cave Explorers Club, the Israel Cave Research Center at the Hebrew University of Jerusalem and the Caving Club and Speleo School “Sofia”, Bulgaria. 

The expedition is supported by the Bulgarian Federation of Speleology, the Ministry of Youth and Sports in Bulgaria, the European Federation of Speleology and FSE official partners: Aventure Verticale, Korda’s, Scurion. “Bulgaria air” is an official partner and carrier of the Bulgarian participants of the expedition.

Additional information

Mount Sedom, Dead Sea, Israel

Mount Sedom is a mountain along the southwestern part of the Dead Sea in Israel, part of Negev Desert. It is only 11 km long and approximately 2 km wide. The mountain top is 226 m above the Dead Sea and reaches a height of 170 m below sea level.

Mount Sedom is an extraordinary geological phenomenon: underneath some thin layers of sand, anhydrite, silt and marl, it is made entirely of salt. The general geology includes two rock units: karstic and non-karstic. The karstic unit is a massive salt rock and the non-karstic unit comprise less soluble minerals (mainly anhydrite) and lacustrine deposits (clay, sand etc.), usually named “cap rock”. Two factors protecting the salt rock from total dissolution are – the cap rock covering the salt, and the aridity of the area. The salt layers accumulated in a lagoon connected to the Mediterranean Sea about 8 million years ago. The weight of the rocks above creates a pressure that forces the salt to flow up along the basin wall, creating a salt diapir (intruding structure).

The mountain is an outcome of this massive force, and it keeps rising approximately 1 cm per year. The mountain gets around 50 mm of rain a year, which appear as short but dramatic rain storms. The short rains turn into flash-floods. Part of the water is drained from the mountain on the surface, but most of the water is drained through the cap rock into the salt layers forming underground channels (allogenic karst). Contrary to other rocks, the salt dissolves extremely rapidly in water. Erosion and creation of underground cavities in salt are an order of magnitude faster than in limestone or dolomite.

Salt Caves of Mount Sedom

Mount Sedom caves are underground dry and active water streams. The source of the stream is local flash-floods, on the less-permeable cap rock. Some surface streams are captured downwards into the cap rock, becoming underground passages. When the stream reaches the salt layer it drops in a vertical shaft until it reaches an underground tunnel that has enough capacity to drain the flood water out of the shaft. Those underground passages are semi-horizontal channels. The caves of Mount Sedom are divided into 2 classes, caves that has an outlet (traverse caves) and caves that have no human-negotiable outlet (inlet caves). In this case an underground salt-water lakes may form.

The deepest cave is around 135 m. There are about 150 known caves and each year there are new discoveries. The oldest cave is only 8000 years old.

Malham Caving Expedition 2019 Teaser by Radu Dimitru, Romania

Malham Cave Project – The Longest Salt Cave in The World by Boyan Shanov

Photos from the expedition by Efraim Cohen, Marketa Jakovenko, Boyan Shanov, Antoniya Vlaykova