Marrah Mountains

The Marrah Mountains or Marra Mountains (Fur, Fugo Marra; Arabic: جبل مرة, Jebel Marra) are a range of volcanic peaks in a massif that rises up to 3,012 metres (9,882 ft). They are the highest mountains in Sudan.

The mountains are located in the center of the Darfur region of Sudan on the border of the states of South Darfur and Central Darfur, with a smaller part of the range in the state of North Darfur. The highest point is Deriba Caldera. The upper reaches of the massif is a small area of temperate climate with high rainfall and permanent springs of water amidst the dry savanna and scrub of the Sahel below.

Apart from the Aïr Mountains in Niger, which are on the border of the Sahara proper, the Marrah Mountains are the only major mountain range in the otherwise flat Sahel, rising up to 2,600 metres (8,500 ft) above the plain, but are relatively unknown owing to lack of development and political conflict in the region.

The last eruption occurred around 1500 BC. The centre of activity was Deriba Caldera, and involved caldera collapse following the eruption of pumice and pyroclastic flows which travelled over 30 kilometres (19 mi) from the volcano.

The vegetation was described by Gerald Wickens.

The two lakes at Deriba, as described by Hobbs' 1918 notes, were presumably the only two in Jebel Marra. Hobbs situated them at an altitude of approximately 518 m (1700 feet, as indicated in his note) above the plain and 1,463 m (4,804 feet) above sea level (modern measurements, however, indicate 2100 m). They were described as being located within a vast amphitheatre, approximately 4.8 to 6.4 km (3 to 4 miles) in diameter, formed by a continuous circular (or slightly oval) range of steeply sloping heights, varying from about 244 to 610 m (800 to 2,000 feet) above the surrounding area.

The larger lake, known as the "female", lay in the northeast corner of the amphitheatre. It measured approximately 1,780 metres (5,840 ft) in length, 1,230 metres (4,040 ft) in width, and had a circumference of about 4.8 kilometres (3.0 mi). Its water, with a high salinity, appeared murky green and emitted an unpleasant odour. Although time constraints prevented soundings, it was inferred that the lake was shallow except in its northern part. The smaller lake, dubbed as "male", situated around 800 metres (2,600 ft) south, had fresher water. Its dimensions were approximately 1,420 metres (4,660 ft) in length, 820 metres (2,690 ft) in width, with a circumference of about 910 metres (2,990 ft). Rising nearly vertically from the water's edge, the crater walls reached heights of around 120–210 metres (390–690 ft), except for the northern rim, which sloped gently. Like its counterpart, this lake exhibited a greenish hue and a faint sulphuric aroma.

Since the first exploration by Hobbs and Gillan in 1918 (Gillan 1918, Hobbs 1918.), Jebel Marra has been visited by many geologists, botanists and zoologists. In 1964 an expedition made the first biological survey of the streams and two Deriba lakes. The hydrobiological importance of Jebel Marra stems from the isolation of these waters near the geographical centre of the African continent, coupled with the known chemical differences between the various streams and lakes (Hunting Technical Services, 1958). During the five-week expedition, numerous samples were collected from various sites, including the two saline crater lakes. Chemical analyses were conducted both in the field and at the University of Khartoum. The team also conducted the first bathymetric survey of the lakes, using a calibrated echo sounder and an inflatable rubber dinghy. The larger lake was found to be shallow, with a maximum depth of 11.6 metres (38 ft), while the smaller lake featured unique characteristics, including a conical funnel.