Sof Omar Caves

Sof Omar Caves, located east of Ginnir in Ethiopia’s East Bale Zone, Oromia Region, stretches 15.1 kilometers (9.4 miles), making it the country’s longest cave. When surveyed in 1972, it held the title of Africa’s longest cave, but later discoveries—Marosakabe in Madagascar (113 km) and Rhar Bou Ma’za (the Tafna River Cave) in Algeria (18.4 km)—have since surpassed it. The Weyib River (also called the Gestro River) flows through the cave, sinking at the Ayiew Maco entrance and reappearing 1 kilometer (0.62 miles) away at the Holuca resurgence. According to local tradition, Sof Omar was a Muslim holy man who once lived here, and Ayiew was his daughter; Maco and Holuca are local words for “name” and “cave,” respectively. The site has long served as a religious center, sacred to both Islam and the traditional Oromo faith. The caves are noted for their many pillars, especially in the “Chamber of Columns.” In 2011, the site was added to UNESCO’s tentative list, pending consideration for full inscription.

The first recorded visit by an explorer was in 1894 by Arthur Donaldson Smith. An Italian expedition followed in 1913, and in 1934 Henri Breuil conducted archaeological work in the area. Italians likely visited during their occupation of Ethiopia, but none of these early explorers made a through trip from Ayiew Maco to Holuca. In 1967, Eric Robson, Chris Clapham, and Kabir Ahmed surveyed the cave, mapping 8 kilometers of passage, after which the Ethiopian Tourist Board published a brochure. Though the area was remote and adventure tourism was undeveloped, a few intrepid visitors made the journey. In February 1971, Professor Théodore Monod, Bill Morton, and Ato Mezmure Hailemeskale added another kilometer of passages. That same year, Dick Ashford and Malcolm Largen studied the cave’s bats. In 1972, a British expedition—including Dick Ramsden, Tim Renvoize, Simon Amatt, Dave Catlin, Paul Ramsden, Terry Raynor, and Steve Worthington—systematically explored and surveyed the caves, discovering 6.1 kilometers (3.8 miles) of new passages and bringing the total to 15.1 kilometers (9.4 miles). Their findings were published in the Transactions of the Cave Research Group of Great Britain.

Approaching from Goro, the scrubby bush drops steeply 90 meters into a canyon at Sof Omar. The Web River flows from the 4,300-meter (14,100-foot) Bale Mountains through a 150-kilometer (93-mile) wide outcrop of Anatole limestone to the cave. In earlier times, the river made a sharp left meander; over time, limestone dissolved, creating phreatic passages large enough to capture the entire river flow. The river eventually abandoned the meander, leaving a dry valley from the sink at Ayiew Maco to the resurgence at Holuca. Sof Omar village lies near Ayiew Maco in this dry valley. Infill has raised the valley to about 45 meters above the Web, before it drops to a pebble beach downstream of Holuca. Another dominant feature is a large shakehole 100 meters (330 feet) wide and 60 meters (200 feet) deep on the basalt plateau above the cave.

The cave follows a network of joints: one set runs roughly north-south, the other east-west, creating a zigzag of passages trending southeast. Sof Omar has 42 entrances, but only four are commonly used: two upstream Village Entrances (one east, one west of the village), the Tourist Entrance downstream from the Holuca Resurgence where the dry valley rejoins the Web River, and a right bank entrance downstream of Holuca that accesses the Deep South part of Clapham’s Climb Series. Entering via either Village Entrance, visitors pass a local shrine. The Ayiew Maco Series consists of interconnecting passages 1 to 10 meters wide, several leading to a pebble beach on the river’s left bank. A less complex series on the right bank probably once connected to the left bank until the Web’s vadose action cut the river passage deeper.

At the pebble beach, the passage is about 40 meters wide—the cave’s widest. Downstream, the river vanishes between two columns. The route crosses the Web at Ford 1, follows a figure-eight passage, and reaches the river again at Ford 2. The river meanders through a rectangular passage 15 meters wide and 20 meters high for 300 meters. The way onward involves crossing and recrossing the river at Fords 2, 3, 4, and 5. Small passages exist on both sides. The beach ends after Ford 5 beneath the 50-meter-high Great Dome. On the opposite bank, a steep rise leads to Molossadie Passage. Short, deep Fords 6, 7, and 8 lead to a cobble beach and the entrance to the Chamber of Columns. Exiting Ford 6 on the left bank, the Railway Tunnel passage offers an alternative route into Molossadie Passage, bypassing Fords 7 and 8 into the Chamber of Columns.