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May Zegzeg
May Zegzeg is a river of the Nile basin. Rising in the mountains of Dogu’a Tembien in northern Ethiopia, it flows southward to empty finally in Giba and Tekezé River. Characteristics It is a confined river, locally meandering in its narrow alluvial plain, with an average slope gradient of 43 metres per kilometre. With its tributaries May Sho'ate and May Harena, the river has cut a gorge. Jointly with adjacent May Be’ati River, this river is the source of Rubaksa River. Flash floods and flood buffering Runoff mostly happens in the form of high runoff discharge events that occur in a very short period (called flash floods). These are related to the steep topography, often little vegetation cover and intense convective rainfall. The peaks of such flash floods have often a 50 to 100 times larger discharge than the preceding baseflow. The magnitude of floods in this river has however been decreased due to interventions in the catchment. At Habdi Luqmuts and on other steep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tigrinya Language
(; also spelled Tigrigna) is an Ethio-Semitic language commonly spoken Eritrea and in northern Ethiopia's Tigray Region by the Tigrinya and Tigrayan peoples. It is also spoken by the global diaspora of these regions. History and literature Although it differs markedly from the Geʽez (Classical Ethiopic) language, for instance in having phrasal verbs, and in using a word order that places the main verb last instead of first in the sentence—there is a strong influence of Geʽez on Tigrinya literature, especially with terms relating to Christian life, Biblical names, and so on. Ge'ez, because of its status in Ethiopian culture, and possibly also its simple structure, acted as a literary medium until relatively recent times. The earliest written example of Tigrinya is a text of local laws found in the district of Logosarda, Debub Region in Southern Eritrea, which dates from the 13th century. In Eritrea, during British administration, the Ministry of Information put out a we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Confluence MB MZZ
In geography, a confluence (also: ''conflux'') occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main stem); or where two streams meet to become the source of a river of a new name (such as the confluence of the Monongahela and Allegheny rivers at Pittsburgh, forming the Ohio); or where two separated channels of a river (forming a river island) rejoin at the downstream end. Scientific study of confluences Confluences are studied in a variety of sciences. Hydrology studies the characteristic flow patterns of confluences and how they give rise to patterns of erosion, bars, and scour pools. The water flows and their consequences are often studied with mathematical models. Confluences are relevant to the distribution of living organisms (i.e., ecology) as well; "the general pattern ownstream of confluencesof increasing stream flow and decreasing sl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene (2.58 million years ago to 11.7 thousand years ago) and the Holocene (11.7 thousand years ago to today, although a third epoch, the Anthropocene, has been proposed but is not yet officially recognised by the ICS). The Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets related to the Milankovitch cycles and the associated climate and environmental changes that they caused. Research history In 1759 Giovanni Arduino proposed that the geological strata of northern Italy could be divided into four successive formations or "orders" ( it, quattro ordini). The term "quaternary" was introduced by Jules Desnoye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antalo Limestone
The Antalo Limestone, also known as the Antalo Sequence, is a geological formation in Ethiopia. It is between 300 and 800 metres thick and comprises fossiliferous limestones and marls that were deposited in a reef. Marine microfossils have shown an age between 165 and 150 million years. Name and definition The Antalo Supersequence includes two main stratigraphic units: the Antalo Sequence and the Agula Group. The Antalo Sequence, or Antalo Limestone has been named after the town of Hintalo in Tigray, Ethiopia. The name of the formation was coined by geologist William Thomas Blanford, who accompanied the British Expedition to Abyssinia in 1868. At that time, Hintalo was a major town on the route of the invading British army. So far the nomenclature has not been proposed for recognition to the International Commission on Stratigraphy. Geographical extent The sedimentary succession is found in Ethiopia, in the Mekelle Outlier, in the Blue Nile gorge, in the Harrar Plateau and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amba Aradam Formation
The Amba Aradam Formation is a Cretaceous sandstone formation in Ethiopia. It is up to 200 metres thick, for instance in the Degua Tembien district. As fossils are absent, the age of the Amba Aradam Formation was interpreted based on the age of assumed corresponding sandstones elsewhere in Ethiopia: the Debre Libanos Sandstones in the Blue Nile Basin, and the Upper Sandstone near Harrar in southeast Ethiopia, both of Late Cretaceous age (100–66 million years ago). The lithology of the Amba Aradam Formation makes it less suitable for rock church excavation; caves have however been blasted in this formation to serve as headquarters for the TPLF during the Ethiopian Civil War of the 1980s. Name and definition The name “Amba Aradam Sandstone” was coined by geologist William Thomas Blanford, who accompanied the British invading army in 1868. The formation is named after the Amba Aradam mountain, where the formation widely outcrops. So far the nomenclature was not proposed for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ashangi Basalts
The Ashangi Basalts are the earliest Tertiary volcanic rocks in north Ethiopia, hence they are in the lowest position. These dark porphyritic basalts are separated from the Mesozoic formations below it by basal Conglomerate (geology), conglomerates. The basalts hold phenocrysts that developed before the magma reached the earth surface. These basalts are weathered, partially eroded and have a sub-horizontal stratification, particularly at the lower part. This series was created during the first period of the flood basalt eruptions in north Ethiopia, in the Oligocene. Name and definition The name was coined by geologist William Thomas Blanford, who accompanied the British Expedition to Abyssinia in 1868,{{cite book , last1=Blanford , first1=W.T. , title=Observations on the geology and zoology of Abyssinia, made during the progress of the British expedition to that country in 1867-68 , url=https://archive.org/details/cu31924024736666 , date=1870 , publisher=Macmillan and Co. , location ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intra-volcanic Sedimentary Rock In North Ethiopia
Between 29 and 27 million years ago, the extrusion of Ethiopia’s flood basalts was interrupted and deposition of continental sediments occurred. Inter-trappean beds outcrop in many places of the Ethiopian highlands. They consist of fluvio-lacustrine deposits, that are generally a few tens of metres thick. Often, these interbedded fluvio-lacustrine deposits are very visible because their bright colours strongly contrast with the basalt environment. Name and definition The formation, also called ''silicified limestone'' and ''interbedded lacustrine deposits'' was first extensively characterised in the 1930s by Merla and Minucci. Stratigraphic context The formation is generally at the interface between the lower Ashangi Basalts, and the upper Alaji Basalts. Environment The sediments were deposited in shallow lakes and marshes in large topographic depressions. The dense vegetation hosted mammals and birds, which found their food between the reeds of the lake shores. The decompos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alaji Basalts
The Alaji (upper) Basalts are the youngest series of the Ethiopian flood basalts. The most recent flows are only 15 million years old. Name and definition The name was coined by geologist William Thomas Blanford, who accompanied the British Expedition to Abyssinia in 1868, after the Imba Alaje mountain. So far the nomenclature has not been proposed for recognition to the International Commission on Stratigraphy. Stratigraphic context Uppermost Tertiary flood basalts in Ethiopia. Locally they are covered by Pliocene shield volcanoes, such as the Simien Mountains, or Mount Guna. These flows have been deposited on the lower Ashangi Basalts and locally on intra-volcanic sedimentary rock. Environment Like all volcanic rocks, the Alaji Basalts originate from initial melting of the Earth's mantle. After extrusion, the magmatic structures form at the surface. Common volcanic structures such as lava tubes or ropy lavas are absent in the Alaji Basalts, but (columnar joints) are omnipres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonolite Series In North Ethiopia
The phonolite or clinkstone of northern Ethiopia is a shallow-seated igneous rock. The phonolites intruded and punctured the Mesozoic sedimentary rocks and the Tertiary flood basalts some 19 to 11 million years ago. Stratigraphic context The formation occurs as plugs that have punctured the Tertiary flood basalts of the Ethiopian plateau, and form the highest peaks in their surrounding. Lithology These phonolites are composed of alkali pyroxenes and nephelines; there are also elongated plagioclase crystals. Pyroxenes have a skeletal texture, whereas nepheline crystals are hexagonal to rectangular. The phonolites of pink to light grey colour. The outcrops hold massive (up to 25 metres long), moderately weathered blocks, generally of elongated shape; in some locations it also forms spherical outcrops. Geographical extent These silica-poor rocks belong to the Adwa-Aksum trachy-phonolite volcanic field. They are also exposed in Addi Amyuq, some 3 kilometres north of Hagere Selam, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Check Dam
A steel check dam A check dam is a small, sometimes temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity. Check dams themselves are not a type of new technology; rather, they are an ancient technique dating from the second century A.D. Check dams are typically, though not always, implemented in a system of several dams situated at regular intervals across the area of interest. Function A check dam placed in the ditch, swale, or channel interrupts the flow of water and flattens the gradient of the channel, thereby reducing the velocity. In turn, this obstruction induces infiltration and reduces eroding. They can be used not only to slow flow velocity but also to distribute flows across a swale to avoid preferential paths and guide flows toward vegetation. Although some sedimentation may result behind the dam, check dams do not primarily function as sediment-trapping devices. For instance, on the Graliwdo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terrace (earthworks)
In agriculture, a terrace is a piece of sloped plane that has been cut into a series of successively receding flat surfaces or platforms, which resemble steps, for the purposes of more effective farming. This type of landscaping is therefore called terracing. Graduated terrace steps are commonly used to farm on hilly or mountainous terrain. Terraced fields decrease both erosion and surface runoff, and may be used to support growing crops that require irrigation, such as rice. The Rice Terraces of the Philippine Cordilleras have been designated as a UNESCO World Heritage Site because of the significance of this technique. Uses Terraced paddy fields are used widely in rice, wheat and barley farming in east, south, southwest, and southeast Asia, as well as the Mediterranean Basin, Africa, and South America. Drier-climate terrace farming is common throughout the Mediterranean Basin, where they are used for vineyards, olive trees, cork oak, and other crops. Ancient history ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infiltration (hydrology)
Infiltration is the process by which water on the ground surface enters the soil. It is commonly used in both hydrology and soil sciences. The infiltration capacity is defined as the maximum rate of infiltration. It is most often measured in meters per day but can also be measured in other units of distance over time if necessary. The infiltration capacity decreases as the soil moisture content of soils surface layers increases. If the precipitation rate exceeds the infiltration rate, runoff will usually occur unless there is some physical barrier. Infiltrometers, permeameters and rainfall simulators are all devices that can be used to measure infiltration rates. Infiltration is caused by multiple factors including; gravity, capillary forces, adsorption and osmosis. Many soil characteristics can also play a role in determining the rate at which infiltration occurs. Factors that affect infiltration Precipitation and Precipitation can impact infiltration in many ways. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
