TY - JOUR
T1 - Geological and geotechnical properties of the medieval rock hewn churches of Lalibela, Northern Ethiopia
AU - Asrat, Asfawossen
AU - Ayallew, Yodit
N1 - Funding Information:
This work was conducted under a research project on ‘Geotourism in Ethiopia’ funded by the Ministry of Science and Technology of Ethiopia (to AA) and an MSc thesis project on the engineering geological characteristics of the Lalibela rock hewn churches funded by the Addis Ababa University (to AA and YA). We would like to acknowledge M. Gobezie, M. Demissie, and A. Mogessie for the fruitful discussions on the history and archaeology of Lalibela as well as the geo-touristic significance of the rock hewn churches. The comments of two anonymous reviewers on the original manuscript are greatly appreciated.
PY - 2011/1
Y1 - 2011/1
N2 - Lalibela is a medieval settlement in Northern Ethiopia famous for its 11 beautifully carved rock hewn churches, registered as World Heritage Site in 1978. The rock hewn churches are grouped into three based on their proximity: the Bete Medhane Alem (Church of the Holy Saviour), Bete Gabriel-Rufael (Church of St. Gabriel-Rafael) and Bete Giorgis (Church of St. George) groups. The churches are carved out of a single, massive scoriaceous basalt hill which was deposited along an East-West extending palaeovalley in the Oligo-Miocene Trap basalt of the northwestern Ethiopian plateau.The Rock Mass Rating (RMR) classification scheme was used to classify the rock mass (assuming each church as a separate rock mass) based on their uniaxial compressive strength and the spacing and conditions of discontinuities. Though most of the churches are hewn from medium to high strength rock mass, discontinuities make them vulnerable to other deteriorating agents mainly weathering, and water infiltration. Most of the rock hewn churches are affected by pre-carving cooling joints and bedding plane discontinuities, and by mostly but not necessarily post-carving tectonic and seismic induced cracks and fractures. Material loss due to deep weathering triggered by rain water infiltration and uncontrolled groundwater seepage affects most of the churches, particularly the Bete Merqorios (Church of St. Mark) and Bete Aba Libanos (Church of Father Libanos) churches. The scoriaceous basalt which is porous and permeable allows easy passage of water while the underlying basalt is impermeable, increasing the residence time of water in the porous material, causing deep weathering and subsequent loss of material in some of the churches and adjoining courtyards.
AB - Lalibela is a medieval settlement in Northern Ethiopia famous for its 11 beautifully carved rock hewn churches, registered as World Heritage Site in 1978. The rock hewn churches are grouped into three based on their proximity: the Bete Medhane Alem (Church of the Holy Saviour), Bete Gabriel-Rufael (Church of St. Gabriel-Rafael) and Bete Giorgis (Church of St. George) groups. The churches are carved out of a single, massive scoriaceous basalt hill which was deposited along an East-West extending palaeovalley in the Oligo-Miocene Trap basalt of the northwestern Ethiopian plateau.The Rock Mass Rating (RMR) classification scheme was used to classify the rock mass (assuming each church as a separate rock mass) based on their uniaxial compressive strength and the spacing and conditions of discontinuities. Though most of the churches are hewn from medium to high strength rock mass, discontinuities make them vulnerable to other deteriorating agents mainly weathering, and water infiltration. Most of the rock hewn churches are affected by pre-carving cooling joints and bedding plane discontinuities, and by mostly but not necessarily post-carving tectonic and seismic induced cracks and fractures. Material loss due to deep weathering triggered by rain water infiltration and uncontrolled groundwater seepage affects most of the churches, particularly the Bete Merqorios (Church of St. Mark) and Bete Aba Libanos (Church of Father Libanos) churches. The scoriaceous basalt which is porous and permeable allows easy passage of water while the underlying basalt is impermeable, increasing the residence time of water in the porous material, causing deep weathering and subsequent loss of material in some of the churches and adjoining courtyards.
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U2 - 10.1016/j.jafrearsci.2010.08.003
DO - 10.1016/j.jafrearsci.2010.08.003
M3 - Article
AN - SCOPUS:78449287896
VL - 59
SP - 61
EP - 73
JO - Journal of African Earth Sciences
JF - Journal of African Earth Sciences
SN - 1464-343X
IS - 1
ER -