Northern Afar Rift
Geology of the Northern Afar Rift
The Northern Afar region (also known as the Danakil Depression) is bound to the west by the Ethiopian Plateau and to the east by the Danakil Block. It is a low lying area dropping in elevation from around 200m in the north to 120m below sea level in its centre. The northwest-southeast trending Axial Volcanic Ranges of the Erta Ale, Tat Ale and Alyata volcanic shield complexes dominate the geology (e.g. Beyene & Abdelsalam, 2005).
To the north of the Northern Afar Rift the southern Red Sea spreading ridge splits into southeast and a SSW trending branches. The southeast trending rift dies out while the SSW trend continues through the Gulf of Zula into the Northern Afar Rift. It continues south along the Erta Ale range and then splits again running southeast into the Tat Ale-Dadar range and southwest into the Alyata-Manda Hararo and Dabbahu ranges (Barberi & Varet, 1975, Chu & Gordon, 1998, Beyene & Abdelsalam, 2005) .
Within
the Northern Afar Rift, Quaternary extension has thinned the crust to
about 16km and the rift is below sea level. This extension is accompanied
by magmatism which has formed the NW-SE trending axial volcanic ranges
of fissure basalts and shield volcanoes. The axial volcanic ranges are
up to 80km long and 700m high. They are cut by a series of horsts and
grabens getting younger towards the centre and formed by short, closely
spaced normal faults. Transfer zones between the normal faults form topographic
lows with adjacent segments curving together in a similar manner to en
echelon fracture tips and oceanic ridge segments (Hayward & Ebinger,
1996).
Top: Looking north along the Dabbahu rift segment towards the Dabbahu volcano (Photo by Elizabeth Baker, Royal Holloway, University of London.) Left: Close up showing the geometry of the normal faults and transfer zones (Photo by Elizabeth Baker, Royal Holloway, University of London.)
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