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Kenyte
Kenyte is a type of igneous rock. More specifically, it is a variety of porphyritic phonolite or trachyte with rhomb-shaped phenocrysts of anorthoclase with variable amounts of olivine and augite in a glassy matrix; the glass may be devitrified. It was originally described and named by J. W. Gregory in 1900 for the occurrence on Mount Kenya. Kenyte has also been reported from Mount Kilimanjaro (Tanzania) and Mount Erebus Mount Erebus () is the second-highest volcano in Antarctica (after Mount Sidley), the highest active volcano in Antarctica, and the southernmost active volcano on Earth. It is the sixth-highest ultra mountain on the continent. With a summ ... (Antarctica).Kyle, Philip R., ed., ''Volcanological and Environmental Studies of Mount Erebus, Antarctica,'' American Geophysical Union (December 1994), p. ''xi'' References Volcanic rocks Igneous petrology Mount Kenya Geology of Kenya Volcanism of Antarctica {{petrology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Kenya
Mount Kenya (Kikuyu: ''Kĩrĩnyaga'', Kamba, ''Ki Nyaa'') is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian (), Nelion () and Point Lenana (). Mount Kenya is located in the former Eastern and Central provinces of Kenya; its peak is now the intersection of Meru, Embu, Laikipia, Kirinyaga, Nyeri and Tharaka Nithi counties, about south of the equator, around north-northeast of the capital Nairobi. Mount Kenya is the source of the name of the Republic of Kenya. Mount Kenya is a volcano created approximately 3 million years after the opening of the East African Rift. Before glaciation, it was high. It was covered by an ice cap for thousands of years. This has resulted in very eroded slopes and numerous valleys radiating from the peak. There are currently 11 small glaciers, which are shrinking rapidly, and may disappear by 2050. The forested slopes are an important source of water for much of Keny ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kenyte From Mount Kenya
Kenyte is a type of igneous rock. More specifically, it is a variety of porphyritic phonolite or trachyte with rhomb-shaped phenocrysts of anorthoclase with variable amounts of olivine and augite in a glassy matrix; the glass may be devitrified. It was originally described and named by J. W. Gregory in 1900 for the occurrence on Mount Kenya. Kenyte has also been reported from Mount Kilimanjaro (Tanzania) and Mount Erebus Mount Erebus () is the second-highest volcano in Antarctica (after Mount Sidley), the highest active volcano in Antarctica, and the southernmost active volcano on Earth. It is the sixth-highest ultra mountain on the continent. With a summ ... (Antarctica).Kyle, Philip R., ed., ''Volcanological and Environmental Studies of Mount Erebus, Antarctica,'' American Geophysical Union (December 1994), p. ''xi'' References Volcanic rocks Igneous petrology Mount Kenya Geology of Kenya Volcanism of Antarctica {{petrology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Matrix (geology)
The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded. The matrix of an igneous rock consists of finer-grained, often microscopic, crystals in which larger crystals, called phenocrysts, are embedded. This porphyritic texture is indicative of multi-stage cooling of magma. For example, porphyritic andesite will have large phenocrysts of plagioclase in a fine-grained matrix. Also in South Africa, diamonds are often mined from a matrix of weathered clay-like rock (kimberlite) called "yellow ground". The matrix of sedimentary rocks is finer-grained sedimentary material, such as clay or silt, in which larger grains or clasts are embedded. It is also used to describe the rock material in which a fossil is embedded. Cementation All sediments are at first in an incoherent condition (e.g. sands, clays and gravels, beds of shells), and they may remain in this state for an indefinite period. Millions of years have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Petrology
Igneous petrology is the study of igneous rocks—those that are formed from magma. As a branch of geology, igneous petrology is closely related to volcanology, tectonophysics, and petrology in general. The modern study of igneous rocks utilizes a number of techniques, some of them developed in the fields of chemistry, physics, or other earth sciences. Petrography, crystallography, and isotopic studies are common methods used in igneous petrology. Methods Determination of chemical composition The composition of igneous rocks and minerals can be determined via a variety of methods of varying ease, cost, and complexity. The simplest method is observation of hand samples with the naked eye and/or with a hand lens. This can be used to gauge the general mineralogical composition of the rock, which gives an insight into the composition. A more precise but still relatively inexpensive way to identify minerals (and thereby the bulk chemical composition of the rock) with a petrographic m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Rocks
Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of Volcano, volcanic origin. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into Subvolcanic rock, hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks. For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In the context of Precambrian shield (geology), shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks. Volcanic rocks and sediment that form from magma erupted into the air are called "volcaniclastics," and these are technically sedimentary rocks. Volcanic rocks are among the most common rock types on Earth's surface, particularly in the oceans. On land, they are very common at plate bound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Erebus
Mount Erebus () is the second-highest volcano in Antarctica (after Mount Sidley), the highest active volcano in Antarctica, and the southernmost active volcano on Earth. It is the sixth-highest ultra mountain on the continent. With a summit elevation of , it is located in the Ross Dependency on Ross Island, which is also home to three inactive volcanoes: Mount Terror, Mount Bird, and Mount Terra Nova. The volcano has been active since about 1.3 million years ago and has a long-lived lava lake in its inner summit crater that has been present since at least the early 1970s. The volcano was the site of the Air New Zealand Flight 901 accident, which occurred in November 1979. Geology and volcanology Mount Erebus is the world's southernmost active volcano. It is the current eruptive centre of the Erebus hotspot. The summit contains a persistent convecting phonolitic lava lake, one of five long-lasting lava lakes on Earth. Characteristic eruptive activity consists of Str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Kilimanjaro
Mount Kilimanjaro () is a dormant volcano in Tanzania. It has three volcanic cones: Kibo, Mawenzi, and Shira. It is the highest mountain in Africa and the highest free-standing mountain above sea level in the world: above sea level and about above its plateau base. It is the highest volcano in Africa and the Eastern Hemisphere. Kilimanjaro is the fourth most topographically prominent peak on Earth. It is part of Kilimanjaro National Park and is a major hiking and climbing destination. Because of its shrinking glaciers and ice fields, which are projected to disappear between 2025 and 2035, it has been the subject of many scientific studies. Toponymy The origin of the name Kilimanjaro is not known, but a number of theories exist. European explorers had adopted the name by 1860 and reported that Kilimanjaro was the mountain's Kiswahili name. The 1907 edition of ''The Nuttall Encyclopædia'' also records the name of the mountain as Kilima-Njaro. Johann Ludwig Krapf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Walter Gregory
John Walter Gregory, , (27 January 1864 – 2 June 1932) was a British geologist and explorer, known principally for his work on glacial geology and on the geography and geology of Australia and East Africa. The Gregory Rift in the Great Rift Valley is named in his honour. Early life Gregory was born in Bow, London, the only son of a John James Gregory, a wool merchant, and his wife Jane, ''née'' Lewis. Gregory was educated at Stepney Grammar School and at 15 became a clerk at wool sales in London. He later took evening classes at the ''Birkbeck Literary and Scientific Institution'' (now Birkbeck, University of London). He matriculated in 1886, graduated BSc with first-class honours in 1891 and D. Sc. (London) in 1893. In 1887 he was appointed an assistant in the geological department of the Natural History Museum, London. Career Gregory remained at the museum until 1900 and was responsible for a ''Catalogue of the Fossil Bryozoa'' in three volumes (1896, 1899 and 1909), and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Augite
Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid solution in the pyroxene group. Diopside and hedenbergite are important endmembers in augite, but augite can also contain significant aluminium, titanium, and sodium and other elements. The calcium content of augite is limited by a miscibility gap between it and pigeonite and orthopyroxene: when occurring with either of these other pyroxenes, the calcium content of augite is a function of temperature and pressure, but mostly of temperature, and so can be useful in reconstructing temperature histories of rocks. With declining temperature, augite may exsolve lamellae of pigeonite and/or orthopyroxene. There is also a miscibility gap between augite and omphacite, but this gap occurs at higher temperatures. There are no industrial or economic uses for this mineral. Locatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from Partial melting, partial melts of existing rocks in either a Terrestrial planet, planet's mantle (geology), mantle or crust (geology), crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive (geology), extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form Volcanic glass, natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickly on the surface. For this reason, olivine has been proposed as a good candidate for accelerated weathering to sequester carbon dioxide from the Earth's oceans and atmosphere, as part of climate change mitigation. Olivine also has many other historical uses, such as the gemstone peridot (or chrysolite), as well as industrial applications like metalworking processes. The ratio of magnesium to iron varies between the two endmembers of the solid solution series: forsterite (Mg-endmember: ) and fayalite (Fe-endmember: ). Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and fayalite (Fa) (''e.g.'', Fo70Fa30). Forsterite's melting temperature is unusually high at atmospheric pressure, almost , while ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anorthoclase
The mineral anorthoclase ((Na,K)AlSi3O8) is a crystalline solid solution in the alkali feldspar series, in which the sodium-aluminium silicate member exists in larger proportion. It typically consists of between 10 and 36 percent of KAlSi3O8 and between 64 and 90 percent of NaAlSi3O8.Deere, Howie and Zussman, ''Rock Forming Minerals,'' Vol. 4 ''Framework Silicates,'' Wiley, pp. 2 - 5, Fig. 1 Structure and stability Anorthoclase is an intermediate member of the high albite – sanidine alkali feldspar solid solution series. Intermediate members of this series, high albite, anorthoclase and high sodium sanidine are stable at temperatures of and above. Below 400 to 600 °C only very limited solution exists (less than about 5% on both the low albite and microcline ends).Klein, Cornelis and Cornelius S. Hurlbut, Jr. ''Handbook of Mineralogy,'' Wiley, pp. 446-449 (Fig. 11-95 Anorthoclase and high albite exhibit triclinic symmetry, whereas sanidine and the low temperature orthoc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
