In many parts of the world debris flows are one of the most dangerous of all mass wasting events. Mountainous areas with high slope instability, high seismic activities and extreme rainfall condition are the main triggering factors. The Monday, May 12, 2008, mega-earthquake of magnitude 8.0 that struck the Wenchuan area, Northwestern Sichuan province in China was catastrophic. This event, led to co-seismic landslides and subsequent rainfall induced debris flow in Yingxiu catchment on August 14th, 2010. The catchment has a very steep topography, an area of 5.35 km2 and a channel length of 3.55 km. The aim of this research is to model the post seismic debris flow, Parameterize and calibrate the event. Two main initiation zones were identified based on susceptibility assessed from geomorhological mapping and formed the bases for input in the FLO-2D model. 161, 350 m3 (64.54%) of the debris flow volume was modeled with FLO-2D in a manner consistent within the limit of the data available. FLO-2D model do not incorporate entrainment of materials in the transport zone. Thus, limitation to the production of the total deposits volume on the debris flow fan. The model was parameterized and the result shows that, Sediment concentration and the coefficient of friction were the two main parameters that affected the velocity of debris flow, area of inundation and the impact force respectively. Finally, the debris flow was calibrated using a back analysis of the debris flow event of 2010.
This study is the second of a series of work to be done on Bishini Sheet 165 SW, which is part of the basement complex of the Kushiriki-Minna area. The area lies between latitudes 9°34′ N and 9°40′ N and longitudes 7°00′ E and 7°08′ E. Due to the continuous play of geologic processes on the earth, there is the need to continuously update the geology of the Nigeria basement complex as this has a very important economic implication in areas like mineral and water exploration. Equally, less attention has been given to this sheet unlike other sheets within the zone. The study of the block has revealed the various rock types and their geological characteristics: field relation, macroscopic and microscopic features and structural elements. Results from the field shows that the block consists of migmatites, gneisses, schists and granites which all show a variety of colours, textures and mineralogy. The displacement of distinctive mineralogy, textures, optical and structural characteristics led to the nomenclature of the rocks. The granitic rocks displayed two petrographic varieties based on their textures. These are the fine-medium grained and coarse porphyritic varieties. The granitic rocks have greatly intruded other rocks and this is thought to be responsible for gold mineralization in the area, The NNE-SSW and the NNW-SSE are the major structural trends determined for the joints and faults while the minor ones are the NE-SW and NW-SE. All these trends are consistent with the general trends of the Nigeria basement rocks. A study of thin sections of the rocks under a petrological microscope reveals characteristic optical properties peculiar to each rock type. The type and nature of the minerals the rocks contain together with their geometry reveal that the rocks have undergone more than one deformational event since the time of their formation. The occurrence of numerous fractures (joints and faults) shows that the area has a great potential for water and mineral exploration.
A swarm of 14 landslides occurred spontaneously within the Azenge Mountain on November 13 th , 2010 between the hours of 1 and 6 am after torrential rains. The landslides were studied using interviews, field observations and laboratory study of the soil samples collected from the major landslide site. Results of the study show that the event that was reported by many local media in Nigeria as volcanic eruption was a spontaneous massive slope movement along the mountainous terrain of Imande Ukusu, Mon village. About 1,123,918 m 3 of rock and debris were moved along the sliding surface for more than 1.5 km to the toe of the mountain within a very few minutes. The size of the materials moved decreases from the top to the toe of the slope which range from 50 o to 5 o respectively. These materials range in size from block of rocks of various sizes, soil to mud. The largest boulders moved measured 71.2 m and 88.5 m respectively. The rock types in the area include gneisses, granites, basaltic rocks and dolerite dykes which have a general strike of 240 o NW with a dip of 038 o NE and are highly fractured. The fractures and dip are in the direction of the slope. Laboratory result of the soil samples reflect two types of grain sizes. Those with very high degree of susceptibility to sliding above the sliding surface which plot in the failure zone and those less susceptible from the sliding surface and plot outside the failure zone. Torrential rainfall towards the end of the year was the main triggering mechanism of the landslides. Other causes are attributed to geological, morphological and human factors. The landslides led to the death of 1 person, destruction of vegetation, soil structure and texture, farmlands and remodeling of the geomorphology of the area. It is recommended that human activities along the toe of the hills be reduced and settlements should be sited far away from the hills to avoid further loss of lives in future.
The Odobola, Ogodo area is part of the basement complex of Nigeria and is underlain mainly by schists and intrusive granitic and pegmatitic rocks along with sediments weathered from these rocks. The granitic and pegmatitic intrusives are source of feldspar with a significant K2O component (k-feldspar). A study of the area reveals the occurrence of feldspar deposit hosted by granitic and pegmatitic intrusives. Geochemical data for the feldspar samples show average Si2O, Al2O, K2O, Na2O, CaO, Fe2O3, MgO and TiO2 contents of 65.81wt%, 16.67wt%, 10.67wt%, 5.83wt%, 0.02wt%, 0.26wt%, 0.5wt% and < 0.001wt% respectively while mineralogical results reveals average anorthite, orthoclase and albite contents of 0.42%, 85.40% and 14.06% respectively. The results of the analyses compared with those of the British international Standard (BIS) shows that the feldspar deposit can be used in industries such as glass, ceramic tiles, sanitary wares and insulators. Field and petrographic evidence show that the area is a potential source of gemstones such as tourmaline and tantalite. Mineral Resource and Reserve Estimation classify the feldspar resource as an estimated proven feldspar-bearing Reserve of about 119Million tons. Apart from feldspar, inferred Minerals Resource of quartz, tantalite and tourmaline can also be obtained from this area
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