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Monte Roraima
Mount Roraima (; ) is the highest of the Pacaraima chain of tepuis (table-top mountain) or plateaux in South America. It is located at the junction of Brazil, Guyana and Venezuela. A characteristic large flat-topped mountain surrounded by cliffs high. The highest point of Mount Roraima is located on the southern edge of the cliff at an elevation of in Venezuela, and another protrusion at an elevation of at the junction of the three countries in the north of the plateau is the highest point in Guyana. The name Mount Roraima came from the native Pemon people. ''Roroi'' in the Pemon language means "blue-green", and ''ma'' means "great". Leaching caused by intense rainfall has shaped the peculiar topography of the summit, and the geographical isolation of Mount Roraima has made it home to much endemic flora and fauna. Western exploration of Mount Roraima did not begin until the 19th century, when it was first climbed by a British expedition in 1884. Yet despite subsequent expediti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roraima
Roraima ( ) is one of the 26 states of Brazil. Located in the country's North Region, it is the northernmost and most geographically and logistically isolated state in Brazil. It is bordered by the state of Pará to the southeast, Amazonas to the south and west, Venezuela to the north and northwest, and Guyana to the east. The state covers an area of approximately , slightly larger than Belarus, being the fourteenth largest Brazilian state by area. The city of Boa Vista is the capital and largest city in the state, and is the only capital in the country located entirely in the Northern Hemisphere. Antônio Denarium, a member of the conservative Progressistas party, has been the governor of the state since 2019. Roraima is the least populous state in Brazil, with an estimated population of 631,181 inhabitants as of 2020. It is also the state with the lowest population density in Brazil, with 2.01 inhabitants per square kilometre. Its economy, based mainly on the tertiar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pemon
The Pemon or Pemón (Pemong) are Indigenous people living in areas of Venezuela, Brazil, and Guyana.See pp.112,113 and 178 of ''Venezuela: the Pemon'', in '' Condé Nast Traveler'', December 2008. The Pemon people are divided into many dialects and traditions, which are Arekuna, Kamarakoto, and Taurepang. People The Pemon are part of the larger Cariban language family, and include six groups including the Arekuna, Ingarikó, Kamarakoto, Tualipang, Mapoyo and Macushi/Makushi (Macuxi or Makuxi in Brazil). While ethnographic data on these groups are scant, Iris Myers produced one of the most detailed accounts of the Makushi in the 1940s, and her work is heavily relied upon for comparisons between historical and contemporary Makushi life. The Pemon were first encountered by westerners in the 18th century and converted by missionaries to Christianity. Their society is based on trade and considered egalitarian and decentralized, and in Venezuela, funding from petrodollars have help ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astragalus (plant)
''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the List of the largest genera of flowering plants, largest genus of plants in terms of described species. The genus is native to temperate regions of the Northern Hemisphere. Common names include milkvetch (most species), locoweed (in North America, some species) and goat's-thorn (Astragalus gummifer, ''A. gummifer'', Astragalus tragacantha, ''A. tragacantha''). Some pale-flowered vetches (''Vicia'' spp.) are similar in appearance, but they are more vine-like than ''Astragalus''. Description Most species in the genus have pinnately compound leaves. There are annual and perennial species. The flowers are formed in clusters in a raceme, each flower typical of the legume family, with three types of petals: banner, wings, and keel. The Sepal, calyx is tubular or bell-shaped. Taxonomy The genus was formally described in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palmaceae
The Arecaceae () is a family of perennial, flowering plants in the monocot order Arecales. Their growth form can be climbers, shrubs, tree-like and stemless plants, all commonly known as palms. Those having a tree-like form are colloquially called palm trees. Currently, 181 genera with around 2,600 species are known, most of which are restricted to tropical and subtropical climates. Most palms are distinguished by their large, compound, evergreen leaves, known as fronds, arranged at the top of an unbranched stem, except for the Hyphaene genus, who has branched palms. However, palms exhibit an enormous diversity in physical characteristics and inhabit nearly every type of habitat within their range, from rainforests to deserts. Palms are among the best known and most extensively cultivated plant families. They have been important to humans throughout much of history, especially in regions like the Middle East and North Africa. A wide range of common products and foods are deri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orogeny
Orogeny () is a mountain-mountain formation, building process that takes place at a convergent boundary, convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is tectonic uplift, uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation (physics), deformation of existing continental crust and the creation of new continental crust through volcanism. Magma rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's lithosphere (crust (geology), crust and uppermost mantle (geology), mantle). A synorogenic (or synkinematic) process or event is one that occurs during an orogeny. The word ''orogeny'' comes . Although it was used before him, the American geologist Grove Karl Gilbert, G. K. Gilbert used the term in 1890 to me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diorite
Diorite ( ) is an intrusive rock, intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is Intermediate composition, intermediate in composition between low-silica (mafic) gabbro and high-silica (felsic) granite. Diorite is found in mountain-building belts (''orogens'') on the margins of continents. It has the same composition as the fine-grained volcanic rock, andesite, which is also common in orogens. Diorite has been used since prehistoric times as decorative stone. It was used by the Akkadian Empire of Sargon of Akkad for funerary sculptures, and by many later civilizations for sculptures and building stone. Description Diorite is an intrusive rock, intrusive igneous rock composed principally of the silicate minerals plagioclase feldspar (typically andesine), biotite, hornblende, and sometimes pyroxene. The chemical composition of diorite is Intermedia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesozoic
The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian reptiles such as the dinosaurs, and of Gymnosperm, gymnosperms such as cycads, ginkgoaceae and Araucariaceae, araucarian conifers; a hot Greenhouse and icehouse earth, greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of the three eras since Cambrian explosion, complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic. The era began in the wake of the Permian–Triassic extinction event, the largest mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction whose victims included the non-avian dinosaurs, Pterosaur, pterosaurs, Mosasaur, mosasaurs, and Plesiosaur, plesiosaurs. The Mesozoic was a time of significant tectonic, climatic, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gneiss
Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under pressures ranging from 2 to 15 kbar, sometimes even more, and temperatures over 300 °C (572 °F). Gneiss nearly always shows a banded texture characterized by alternating darker and lighter colored bands and without a distinct Cleavage (geology), cleavage. Gneisses are common in the ancient crust of Continental Shield, continental shields. Some of the oldest rocks on Earth are gneisses, such as the Acasta Gneiss. Description image:Orthogneiss Geopark.jpg, Orthogneiss from the Czech Republic In traditional English and North American usage, a gneiss is a coarse-grained metamorphic rock showing compositional banding (gneissic banding) but poorly developed schistosity and indistinct Cleavage (geology), cleavage. In other words, it i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Granite
Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies underground. It is common in the continental crust of Earth, where it is found in igneous intrusions. These range in size from dike (geology), dikes only a few centimeters across to batholiths exposed over hundreds of square kilometers. Granite is typical of a larger family of ''granitic rocks'', or ''granitoids'', that are composed mostly of coarse-grained quartz and feldspars in varying proportions. These rocks are classified by the relative percentages of quartz, alkali feldspar, and plagioclase (the QAPF diagram, QAPF classification), with true granite representing granitic rocks rich in quartz and alkali feldspar. Most granitic rocks also contain mica or amphibole minerals, though a few (known as leucogranites) conta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant families of materials, existing as a compound of several minerals and as a synthetic product. Examples include fused quartz, fumed silica, opal, and aerogels. It is used in structural materials, microelectronics, and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored. Silicon dioxide is a common fundamental constituent of glass. Structure In the majority of silicon dioxides, the silicon atom shows Tetrahedral molecular geometry, tetrahedral coordination, with four oxygen atoms surrounding a central Si atomsee 3-D Unit Cell. Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of Silicon dioxide, SiO2. Quartz is, therefore, classified structurally as a Silicate mineral#Tectosilicates, framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandstone
Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar, because they are the most resistant minerals to the weathering processes at the Earth's surface. Like uncemented sand, sandstone may be imparted any color by impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Because sandstone beds can form highly visible cliffs and other topography, topographic features, certain colors of sandstone have become strongly identified with certain regions, such as the red rock deserts of Arches National Park and other areas of the Southwestern United States, American Southwest. Rock formations composed of sandstone usually allow the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
