Sof Omar Caves
Encyclopedia
At 15.1 kilometres long, Sof Omar Cave is the longest cave
in Ethiopia
; sources claim it is the longest system of caves in Africa
and ranks as the 306th longest in the World. It is situated in the Bale province
in southeastern Ethiopia (6°55′N 40°45′E) through which the Weyib River
(Gestro River) flows. It sinks at the Ayiew Maco entrance and reappears at the Holuca resurgence 1 kilometre (0.621372736649807 mi) away. Long a religious centre, it is sacred both to local traditional religion
s and to Islam
. The caves are known for their many pillars, particularly in the "Chamber of Columns".
The explorer Arthur Donaldson Smith
recorded his visit to the cave in 1894. An Italian expedition also visited in 1913. In 1934, Henri Breuil
conducted some archaeological investigations in the area. The Italians almost certainly visited the cave during the occupation years, but apparently none of these early explorers made a through trip from Ayiew Maco to Holuca.
In 1967, Eric Robson, Chris Clapham and Kabir Ahmed explored and surveyed the cave recording 8 km of passage. Following this the Ethiopian Tourist Board published a brochure about the cave. Although the area was not easily accessible and the "Adventure" Tourist industry did not exist, a few intrepid visitors made the trip to the then remote cave.
In February 1971 Professor Théodore Monod
of the Muséum national d'histoire naturelle
in France, Bill Morton (ex Manchester University Speleological Society caver) a geologist at Haile Selassie I University, and Ato Mejmare Hsilemalid recorded another 1 km new passages to the known cave. In the same year Dick Ashford and Malcolm Largen of Haile Selassie University made a study of some of the bat
s in the cave.
In 1972, the British Expedition to Ethiopia arrived. The team included Dick Ramsden and Tim Renvoize (Preston Caving Club), Simon Amatt (Birmingham Plytechnic Karabiner Club), Dave Catlin (University of Bradford Pothole Club), Paul Ramsden (Whernside Manor Scout Centre), Terry Raynor (9th and 12th Royal Lancers) and Steve Worthington (Sheffield University Speleological Society). With some initial help from Bill Morton the group made a systematic exploration and survey of the cave and published a full report of the Sof Omar caves in the Transactions of the Cave Research Group of Great Britain. The team discovered 6.1 kilometres (3.8 mi) of new passages bringing the survey total to 15.1 kilometres (9.4 mi).
and through a 150 kilometres (93.2 mi) wide outcrop of Anatole Limestone to the cave. In earlier times the river made a sharp left meander. At some point the cave dissolved a series of phreatic
passages, which became big enough to capture the whole flow of the river Web. Eventually the river abandoned the meander creating a dry valley running from the cave sink at Ayiew Maco to the resurgence at Holuca. Sof Omar village is situated close to Ayiew Maco in the dry valley. Infill into the valley makes it rise to a high point of about 45 m above the Web, before it drops away to a pebble beach downstream of Holuca.
The other dominant feature is the large shakehole 100 metres (328.1 ft) wide and 60 metres (196.9 ft) deep. This is found on the basalt
plateau directly above the cave.
Entering the cave via either of the Village Entrances the visitor passes a shrine used by the locals. The Ayiew Maco Series is a set of interconnecting passages of varying in width between 1m and 10m. Several can be passed through to the pebble beach on the left bank of the river. A less complex series of passages exists on the right bank. These probably connected to those on the left bank until severed by the vadose action of the Web cutting the river passage deeper.
The passage at the pebble beach is about 40 m wide – the widest passage in the cave. At the downstream end of the beach the river disappears between two columns. The way to continue is to cross the Web at Ford 1 and follow the Figure-of-Eight passage until reaching the river again at Ford 2. At this point it is possible to see down Safari Straight, the most spectacular view in the cave. The river meanders down this 15m wide, 20m high rectangular passage for 300m.
The way on involves crossing and re-crossing the river from cobble beach to cobble beach at Fords 2, 3, 4 and 5. Small passages exist on both sides. The beach after Ford 5 ends under the 50m high Great Dome. On the opposite bank a steep rise leads to Molossadie Passage. The deep, short Ford 6, Ford 7 and Ford 8 leads to a cobble beach and the entrance into the Chamber of Columns. Exiting Ford 6 on the left bank it is possible to enter the Railway Tunnel passage which offers an alternative route into Molossadie and a bypass to Fords 7 and 8 into the Chamber of Columns.
Chamber of Columns is a unique feature in the world of caves. It looks like a wide passage leaving the Web before sweeping back to the river about a 100 m downstream. The passage is circumnavigates a cluster of thick columns densely packed in the centre of chamber. The Railway Tunnel and Molossadie Passage enter the chamber from the north.
The river passage continues from the Chamber of Columns meandering for about 200m to the Big Rapids. This striking feature is formed from a jumble of huge boulders, well worn by the actions of the river. The river passage continues around a curve for about 250m before flowing around a massive boulder into the sunlight at the Holuca Resurgence. The Web continues running through a canyon. About 250m downstream the dry valley appears on the left bank.
The left side of the canyon
from the resurgence to the dry valley
is riddled with passages breaking out into the canyon walls, forming many of the unusable entrances to the cave. Most of these are small passages exposed as the river cut its way down. The exception to this is the 25m wide Great Hall that follows the north – south
joint pattern breaking into the canyon at the resurgence. Hidden at the end of the Great Hall behind boulders is the hard-to-find Chameleon Passage. This runs along the east–west joint pattern. Some small passages lead from Chameleon to Blank Passage and back to the Big Rapids. Several small passages run from Blank Passage to Boulder Chokes.
The area surrounded by the river, Great Hall, Chameleon and Blank Passage contains a criss-cross labyrinth of passages. Two of the most significant, Bill's Passage and Tautology Passage, run between the river and the Great Hall. These are high rift passages. By climbing them it is possible to access the 35m long Balcony that overlooks the Big Rapids 7m below.
Running parallel to the Great Hall, and interconnected to it via several passages is Flintstone Passage. This splits into lots of different passages that break into the left bank of the canyon downstream of Holuca. Away from the river Flintstone runs into another of the caves' unique passages – Mudwall Passage. This passage has been filled with mud virtually to the 3m high roof. Following the infilling process a vadose trench has been cut the length of the passage revealing that the mud is formed of thin laminations.
After 200 m the Mudwall Passage enters into the small Mudwall Chamber. This has been formed by water coming from Link Passage on the west cutting across the line of the Mudwall Passage disappearing into Rimstone Passage to the east. It is this flow of water that formed the chamber. Climbing out of Mudwall Chamber leads to Batshit Passage whose floor is knee deep in guano
. This leads to the large chamber, the Astrodome, which houses a large colony of bat
s.
Link Passage is a narrow rift passage that links back to the Chamber of Columns. A series of small passages at two levels leave Link Passage and heads towards the river passage. One of these leads into the wide Blind Passage, which also emerges into the Chamber of Columns. The upper passage is a tight crawl into the pretentiously named Wembley Stadium
. This passage is formed in a fault. The survey of the British expedition in 1972 showed that the Wembley Fault extended from a right bank passage on the river, to Wembley Stadium, Mudwall and Rimstone Passages.
The Shakehole on the plateau centred on the Wembley Fault line. Obviously the fault played a significant role in the major collapse that created the Shakehole. The underground debris from the collapse forms the Big Rapids and is responsible for the boulder chokes seen near Blank Passage.
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
in Ethiopia
Ethiopia
Ethiopia , officially known as the Federal Democratic Republic of Ethiopia, is a country located in the Horn of Africa. It is the second-most populous nation in Africa, with over 82 million inhabitants, and the tenth-largest by area, occupying 1,100,000 km2...
; sources claim it is the longest system of caves in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and ranks as the 306th longest in the World. It is situated in the Bale province
Bale Province, Ethiopia
Bale is the name of two former polities located in the southeastern part of modern Ethiopia.- The medieval dependency of Bale :...
in southeastern Ethiopia (6°55′N 40°45′E) through which the Weyib River
Weyib River
Weyib River is a river of eastern Ethiopia. It rises in the Bale Mountains east of Goba in the Oromia Region, flowing east to pass through the Sof Omar Caves, then to the southeast until it joins the Ganale Dorya River in the Somali Region....
(Gestro River) flows. It sinks at the Ayiew Maco entrance and reappears at the Holuca resurgence 1 kilometre (0.621372736649807 mi) away. Long a religious centre, it is sacred both to local traditional religion
Animism
Animism refers to the belief that non-human entities are spiritual beings, or at least embody some kind of life-principle....
s and to Islam
Islam
Islam . The most common are and . : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...
. The caves are known for their many pillars, particularly in the "Chamber of Columns".
History of exploration
According to tradition Sof Omar was the name of a Muslim holy man who lived in the area and Ayiew the name of his daughter. Maco and Holuca are local names for "name" and "cave".The explorer Arthur Donaldson Smith
Arthur Donaldson Smith
Dr. Arthur Donaldson Smith was an American explorer of Africa. In the 1890s he made a geological expedition to Lake Rudolph , passing through what was then Somaliland, southern Ethiopia and Kenya.-External links:*...
recorded his visit to the cave in 1894. An Italian expedition also visited in 1913. In 1934, Henri Breuil
Henri Breuil
Henri Édouard Prosper Breuil , often referred to as Abbé Breuil, was a French Catholic priest, archaeologist, anthropologist, ethnologist and geologist...
conducted some archaeological investigations in the area. The Italians almost certainly visited the cave during the occupation years, but apparently none of these early explorers made a through trip from Ayiew Maco to Holuca.
In 1967, Eric Robson, Chris Clapham and Kabir Ahmed explored and surveyed the cave recording 8 km of passage. Following this the Ethiopian Tourist Board published a brochure about the cave. Although the area was not easily accessible and the "Adventure" Tourist industry did not exist, a few intrepid visitors made the trip to the then remote cave.
In February 1971 Professor Théodore Monod
Théodore Monod
Théodore André Monod was a French naturalist, explorer, and humanist scholar.-Exploration:...
of the Muséum national d'histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...
in France, Bill Morton (ex Manchester University Speleological Society caver) a geologist at Haile Selassie I University, and Ato Mejmare Hsilemalid recorded another 1 km new passages to the known cave. In the same year Dick Ashford and Malcolm Largen of Haile Selassie University made a study of some of the bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s in the cave.
In 1972, the British Expedition to Ethiopia arrived. The team included Dick Ramsden and Tim Renvoize (Preston Caving Club), Simon Amatt (Birmingham Plytechnic Karabiner Club), Dave Catlin (University of Bradford Pothole Club), Paul Ramsden (Whernside Manor Scout Centre), Terry Raynor (9th and 12th Royal Lancers) and Steve Worthington (Sheffield University Speleological Society). With some initial help from Bill Morton the group made a systematic exploration and survey of the cave and published a full report of the Sof Omar caves in the Transactions of the Cave Research Group of Great Britain. The team discovered 6.1 kilometres (3.8 mi) of new passages bringing the survey total to 15.1 kilometres (9.4 mi).
Topography
When you reach Sof Omar from Goro the scrubby bush steeply drops 90 m into a canyon. The river Web makes its way from the 4300 metres (14,107.6 ft) high Bale MountainsBale Mountains
The Bale Mountains are a range of mountains in the Oromia Region of southeast Ethiopia, south of the Awash River. They include Tullu Demtu, the second-highest mountain in Ethiopia , and Mount Batu . The Weyib River, a tributary of the Jubba River, rises in these mountains east of Goba...
and through a 150 kilometres (93.2 mi) wide outcrop of Anatole Limestone to the cave. In earlier times the river made a sharp left meander. At some point the cave dissolved a series of phreatic
Phreatic
The term phreatic is used in Earth sciences to refer to matters relating to ground water below the water table . The term 'phreatic surface' indicates the location where the pore water pressure is under atmospheric conditions...
passages, which became big enough to capture the whole flow of the river Web. Eventually the river abandoned the meander creating a dry valley running from the cave sink at Ayiew Maco to the resurgence at Holuca. Sof Omar village is situated close to Ayiew Maco in the dry valley. Infill into the valley makes it rise to a high point of about 45 m above the Web, before it drops away to a pebble beach downstream of Holuca.
The other dominant feature is the large shakehole 100 metres (328.1 ft) wide and 60 metres (196.9 ft) deep. This is found on the basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
plateau directly above the cave.
Cave description
The cave is formed along a network of joints: one set runs approximately north to south and the other east to west. This zig-zag of passages runs in an approximate southeasterly direction. Sof Omar has 42 entrances, but generally only four are useful for gaining entrance:- Two upstream Village Entrances (one to the east and one to the west of the village)
- The Tourist Entrance downstream from the Holuca Resurgence – at a point where the abandoned meander forming the dry valley rejoins the Web river
- A right bank entrance downstream of Holuca accessing the Deep South part of the Clapham's Climb Series
The passage at the pebble beach is about 40 m wide – the widest passage in the cave. At the downstream end of the beach the river disappears between two columns. The way to continue is to cross the Web at Ford 1 and follow the Figure-of-Eight passage until reaching the river again at Ford 2. At this point it is possible to see down Safari Straight, the most spectacular view in the cave. The river meanders down this 15m wide, 20m high rectangular passage for 300m.
The way on involves crossing and re-crossing the river from cobble beach to cobble beach at Fords 2, 3, 4 and 5. Small passages exist on both sides. The beach after Ford 5 ends under the 50m high Great Dome. On the opposite bank a steep rise leads to Molossadie Passage. The deep, short Ford 6, Ford 7 and Ford 8 leads to a cobble beach and the entrance into the Chamber of Columns. Exiting Ford 6 on the left bank it is possible to enter the Railway Tunnel passage which offers an alternative route into Molossadie and a bypass to Fords 7 and 8 into the Chamber of Columns.
The river passage continues from the Chamber of Columns meandering for about 200m to the Big Rapids. This striking feature is formed from a jumble of huge boulders, well worn by the actions of the river. The river passage continues around a curve for about 250m before flowing around a massive boulder into the sunlight at the Holuca Resurgence. The Web continues running through a canyon. About 250m downstream the dry valley appears on the left bank.
The left side of the canyon
Canyon
A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...
from the resurgence to the dry valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
is riddled with passages breaking out into the canyon walls, forming many of the unusable entrances to the cave. Most of these are small passages exposed as the river cut its way down. The exception to this is the 25m wide Great Hall that follows the north – south
The area surrounded by the river, Great Hall, Chameleon and Blank Passage contains a criss-cross labyrinth of passages. Two of the most significant, Bill's Passage and Tautology Passage, run between the river and the Great Hall. These are high rift passages. By climbing them it is possible to access the 35m long Balcony that overlooks the Big Rapids 7m below.
Running parallel to the Great Hall, and interconnected to it via several passages is Flintstone Passage. This splits into lots of different passages that break into the left bank of the canyon downstream of Holuca. Away from the river Flintstone runs into another of the caves' unique passages – Mudwall Passage. This passage has been filled with mud virtually to the 3m high roof. Following the infilling process a vadose trench has been cut the length of the passage revealing that the mud is formed of thin laminations.
Guano
Guano is the excrement of seabirds, cave dwelling bats, and seals. Guano manure is an effective fertilizer due to its high levels of phosphorus and nitrogen and also its lack of odor. It was an important source of nitrates for gunpowder...
. This leads to the large chamber, the Astrodome, which houses a large colony of bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s.
Link Passage is a narrow rift passage that links back to the Chamber of Columns. A series of small passages at two levels leave Link Passage and heads towards the river passage. One of these leads into the wide Blind Passage, which also emerges into the Chamber of Columns. The upper passage is a tight crawl into the pretentiously named Wembley Stadium
Wembley Stadium
The original Wembley Stadium, officially known as the Empire Stadium, was a football stadium in Wembley, a suburb of north-west London, standing on the site now occupied by the new Wembley Stadium that opened in 2007...
. This passage is formed in a fault. The survey of the British expedition in 1972 showed that the Wembley Fault extended from a right bank passage on the river, to Wembley Stadium, Mudwall and Rimstone Passages.
The Shakehole on the plateau centred on the Wembley Fault line. Obviously the fault played a significant role in the major collapse that created the Shakehole. The underground debris from the collapse forms the Big Rapids and is responsible for the boulder chokes seen near Blank Passage.