It’s official: The 10-kilometer Malham Cave in Israel’s Dead Sea region is the world’s longest salt cave.

The announcement on March 28 followed an international mapping expedition led by the Hebrew University of Jerusalem’s Cave Research Center, Israel Cave Explorers Club and Bulgaria’s Sofia Speleo Club, along with 80 cavers from Israel, Bulgaria, France, United Kingdom, Croatia, Romania, Germany and the Czech Republic.

Looking out of Malham Cave in Israel, the world’s longest salt cave. Photo by Anton Chikishev/Hebrew University

Malham was initially discovered by the Cave Research Center in the 1980s inside 11-kilometer-long Mount Sodom. At 170 meters below sea level at the southwestern tip of the Dead Sea, this mountain is composed entirely of salt underneath a thin layer of cap rock.

Malham Cave near the Dead Sea is inside Mount Sedom, which is made entirely of salt. Photo by Ruslan Paul/Hebrew University

Additional CRC expeditions over the years found more than 100 salt different caves inside the mountain, the longest of which measured 5,685 meters and was dated to approximately 7,000 years ago.

Every winter, rainstorms dissolve more salt and create new passages. So when the international expeditions returned to Malham in 2018 and 2019, they discovered the cave now has a double-digit length, breaking the record held for the past 13 years by Iran’s Cave of the Three Nudes on Qeshm Island, measuring 6,580 meters long.

“Thirty years ago, when we surveyed Malham, we used tape measures and compasses. Now we have laser technology that beams measurements right to our iPhones,” said Prof. Amos Frumkin, director of the CRC at HU’s Institute of Earth Sciences.

However, added his CRC colleague Efraim Cohen, “Mapping Malham Cave took hard work. We cavers worked 10-hour days underground, crawling through icy salt channels, narrowly avoiding salt stalactites and jaw-dropping salt crystals. Down there it felt like another planet.”

Salt stalactites inside Malham Cave near the Dead Sea. Photo by Ruslan Paul/Hebrew University

Currently, the survey team is processing final data from the new Malham Cave surveys to create an electronic map of the cave and to publish its findings.

Cohen said the next and final step is to map the tightest spots and the most difficult ones to reach. “When we’re all done, it’s likely we’ll add a few hundred meters to Malham’s impressive 10-kilometer length.”