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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] |
Degua Tembien
Dogu'a Tembien (, "Upper Tembien", sometimes transliterated as Degua Tembien) is a woreda in Tigray Region, Ethiopia. It is named in part after the former province of Tembien. Nowadays, the mountainous district is part of the Southeastern Tigray Zone. The administrative centre of this woreda is Hagere Selam. History Dogu’a Tembien holds numerous prehistoric sites, which have been dated to the Middle Stone Age in Ayninbirkekin, or Pastoral Neolithic in Aregen and Menachek. Geography Topography and landscapes Major mountains :* Tsatsen, 2815 metres, a wide mesa between Hagere Selam and Inda Maryam Qorar () :* Ekli Imba, 2799 metres, summit of the Arebay massif in Arebay ''tabia'' or district () :* Imba Zuw’ala, 2710 metres, near Hagere Selam () :* Aregen, 2660 metres, in Aregen ''tabia'' () :* Dabba Selama, 2630 metres, in Haddinnet ''tabia'' () (not to be confused with the homonymous monastery) :* Imba Dogu’a, 2610 metres, in Mizane Birhan ''tabia'' () :* Imb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tertiary
Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch. The time span covered by the Tertiary has no exact equivalent in the current geologic time system, but it is essentially the merged Paleogene and Neogene periods, which are informally called the Early Tertiary and the Late Tertiary, respectively. The Tertiary established the Antarctic as an icy island continent. Historical use of the term The term Tertiary was first used by Giovanni Arduino during the mid-18th century. He classified geologic time into primitive (or primary), secondary, and tertiary periods based on observations of geology in Northern Italy. Later a fourth period, the Quaternary, was applied. In the early d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kingdom Of Aksum
The Kingdom of Aksum ( gez, መንግሥተ አክሱም, ), also known as the Kingdom of Axum or the Aksumite Empire, was a kingdom centered in Northeast Africa and South Arabia from Classical antiquity to the Middle Ages. Based primarily in what is now northern Ethiopia, and spanning modern-day Eritrea, northern Djibouti, and eastern Sudan, it extended at its height into much of modern-day southern Arabia during the reign of King Kaleb. Axum served as the kingdom's capital for many centuries but relocated to Jarma in the 9th century due to declining trade connections and recurring external invasions. Emerging from the earlier Dʿmt civilization, the kingdom was likely founded in the early 1st century. Pre-Aksumite culture developed in part due to a South Arabian influence, evident in the use of the Ancient South Arabian script and the practice of Ancient Semitic religion. However, the Geʽez script came into use by the 4th century, and as the kingdom became a major power on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonolite Dimension Stones Khunale
Phonolite is an uncommon extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous rock trachyte that contains nepheline or leucite rather than quartz. Its intrusive equivalent is nepheline syenite. Phonolite is typically fine grained and compact. The name ''phonolite'' comes from the Ancient Greek meaning "sounding stone" due to the metallic sound it produces if an unfractured plate is hit; hence, the English name ''clinkstone'' is given as a synonym. Formation Unusually, phonolite forms from magma with a relatively low silica content, generated by low degrees of partial melting (less than 10%) of highly aluminous rocks of the lower crust such as tonalite, monzonite and metamorphic rocks. Melting of such rocks to a very low degree promotes the liberation of aluminium, potassium, sodium and calcium by melting of fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obelisk Of Axum
The Obelisk of Axum ( ti, ሓወልቲ ኣኽሱም, ḥawelti Akhsum; ) is a 4th-century CE, tall phonolite stele, weighing , in the city of Axum in Ethiopia. It is ornamented with two false doors at the base and features decorations resembling windows on all sides. The obelisk ends in a semi-circular top, which used to be enclosed by metal frames. History Overview The 'obelisk'—properly termed a stele or, in the local languages, Tigrinya: ; and church Ge'ez: —is found along with many other stelae in the city of Axum in modern-day Ethiopia. The stelae were probably carved and erected during the 4th century CE by subjects of the Kingdom of Aksum, an ancient Ethiopian civilization. Erection of stelae in Axum was a very old practice, probably borrowed from the Kushitic kingdom of Meroe. Their function is supposed to be as "markers" for underground burial chambers. The largest of the grave markers were for royal burial chambers and were decorated with multi-story false window ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lioness Of Gobedra
The Lioness of Gobedra is a rock sculpture located in Gobo Dura (Gobedra), Ethiopia. It is a representation of a crouching lioness around three metres long, which was carved into a relief on a large phonolite rock outcropping situated two kilometers west of Axum. It was first described by German archeologists in 1913. The reason for this isolated stone carving is unknown, but the subject of much speculation. A local story, according to Philip Briggs, is that Archangel Michael Michael (; he, מִיכָאֵל, lit=Who is like El od, translit=Mīḵāʾēl; el, Μιχαήλ, translit=Mikhaḗl; la, Michahel; ar, ميخائيل ، مِيكَالَ ، ميكائيل, translit=Mīkāʾīl, Mīkāl, Mīkhāʾīl), also ... was attacked by a lion here, and "he repelled the lion with such force it left an outline in the rock." Not far away is a quarry, where the stelae that adorn Axum are thought to have been carved, and there is a partially-carved example of one.Philip Briggs, '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hagere Selam (Degua Tembien)
Hagere Selam (meaning ''place of peace'') is a town in northern Ethiopia. Located on the Mekelle-Abiy Addi regional road, it is located at an elevation of 2650 metres above sea level. The town is the administrative center of the Dogu'a Tembien woreda. The weekly market is on Saturdays. Hagere Selam is located on the saddle point between two of the higher points in Tigray (Imba Zuw'ala and Tsatsen). The regional road from Mekelle to Abiy Addi climbs towards Hagere Selam, before going down to the Abergele lowlands. The area is categorized as highland or ''dega''. The local economy is dependent on trading, agriculture, with barley being the main crop grown in the area, and on milk production and apiculture. Demographics Based on figures from the census in 2007, Hagere Selam had a total population of 8130, of whom 3702 were men and 4428 were women. The 1994 census reported a total population of 3932. The functional agglomeration of Hagere Selam is larger than its administrative b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rock Sample Phonolite Addi Amyuq
Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales * Rock, Cornwall, a village in England * Rock, County Tyrone, a village in Northern Ireland * Rock, Devon, a location in England * Rock, Neath Port Talbot, a location in Wales * Rock, Northumberland, a village in England * Rock, Somerset, a location in Wales * Rock, West Sussex, a hamlet in Washington, England * Rock, Worcestershire, a village and civil parish in England United States * Rock, Kansas, an unincorporated community * Rock, Michigan, an unincorporated community * Rock, West Virginia, an unincorporated community * Rock, Rock County, Wisconsin, a town in southern Wisconsin * Rock, Wood County, Wisconsin, a town in central Wisconsin Elsewhere * Corregidor, an island in the Philippines also known as "The Rock" * Jamaica, an islan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plagioclase
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series. This was first shown by the German mineralogist Johann Friedrich Christian Hessel (1796–1872) in 1826. The series ranges from albite to anorthite endmembers (with respective compositions NaAlSi3O8 to CaAl2Si2O8), where sodium and calcium atoms can substitute for each other in the mineral's crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or 'record-groove' effect. Plagioclase is a major constituent mineral in the Earth's crust, and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks. Plagioclase is also a major constituent of rock in the highlan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nepheline
Nepheline, also called nephelite (), is a rock-forming mineral in the feldspathoid groupa silica-undersaturated aluminosilicate, Na3 K Al4 Si4 O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites. It is used in glass and ceramic manufacturing and other industries, and has been investigated as an ore of aluminium. Description and properties Nepheline crystals are rare and belong to the hexagonal system, usually having the form of a short, six-sided prism terminated by the basal plane. The crystals appear to have more symmetry than they actually possess, but unsymmetrical etched figures produced artificially on the prism faces indicate that the crystals are hemimorphic and tetartohedral, the only element of symmetry being a polar hexad axis. Nepheline is found in compact, granular aggregates, and can be white, yellow, gray, green, or reddish. Its hardness on the Mohs scale is 5.5–6, and its specific gravity 2.60–2.65. It i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkali Pyroxene
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The adjective alkaline, and less often, alkalescent, is commonly used in English as a synonym for basic, especially for bases soluble in water. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases. Etymology The word "alkali" is derived from Arabic ''al qalīy'' (or ''alkali''), meaning ''the calcined ashes'' (see calcination), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called potash and composed mostly of potassium carbonate, was mildly basic. After heating this substance with calcium hydroxide (''slaked lime''), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flood Basalt
A flood basalt (or plateau basalt) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot reaching the surface of the earth via a mantle plume. Flood basalt provinces such as the Deccan Traps of India are often called '' traps'', after the Swedish word ''trappa'' (meaning "staircase"), due to the characteristic stairstep geomorphology of many associated landscapes. Michael R. Rampino and Richard Stothers (1988) cited eleven distinct flood basalt episodes occurring in the past 250 million years, creating large igneous provinces, lava plateaus, and mountain ranges. However, more have been recognized such as the large Ontong Java Plateau, and the Chilcotin Group, though the latter may be linked to the Columbia River Basalt Group. Large igneous provinces have been connected to five mass extinction events, and may be associated with b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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