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Sahara Desert
The Sahara (, ) is a desert spanning across North Africa. With an area of , it is the largest hot desert in the world and the list of deserts by area, third-largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic. The name "Sahara" is derived from , a broken plural form of ( ), meaning "desert". The desert covers much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile, Nile Valley in Egypt and the Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south it is bounded by the Sahel, a belt of Tropical and subtropical grasslands, savannas, and shrublands, semi-arid tropical savanna around the Niger River valley and the Sudan (region), Sudan region of sub-Saharan Africa. The Sahara can be divided into several regions, including ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apollo 17
Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, while Command Module Pilot Ronald Evans (astronaut), Ronald Evans orbited above. Schmitt was the only professional geologist to land on the Moon; he was selected in place of Joe Engle, as NASA had been under pressure to send a scientist to the Moon. The mission's heavy emphasis on science meant the inclusion of a number of new experiments, including a Fe, Fi, Fo, Fum, and Phooey, biological experiment containing five mice that was carried in the command module. Mission planners had two primary goals in deciding on the landing site: to sample Lunar highlands, lunar highland material older than that at Mare Imbrium and to investigate the possibility of relatively recent Volcano, volcanic activity. They therefore selected Taurus–Littrow, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Niger River
The Niger River ( ; ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in south-eastern Guinea near the Sierra Leone border. It runs in a crescent shape through Mali, Niger, on the border with Benin and then through Nigeria, discharging through a massive River delta, delta, known as the Niger Delta, into the Gulf of Guinea in the Atlantic Ocean. The Niger is the third-longest river in Africa, exceeded by the Nile and the Congo River. Its main tributary is the Benue River. Etymology The Niger has different names in the different languages of the region: * Fula language, Fula: ''Maayo Jaaliba'' * Manding languages, Manding: ''Jeliba'' or ''Joliba'' "great river" * Tuareg languages, Tuareg: ''Eġərəw n-Igərǝwăn'' "river of rivers" * Songhay languages, Songhay: ''Isa'' "the river" * Zarma language, Zarma: ''Isa Beeri'' "great river" * Hausa language, Hausa: ''Kwara'' *Nupe language, Nupe: ''Èdù'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algeria
Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Algeria–Niger border, the southeast by Niger; to Algeria–Western Sahara border, the southwest by Mali, Mauritania, and Western Sahara; to Algeria–Morocco border, the west by Morocco; and to the north by the Mediterranean Sea. The capital and List of cities in Algeria, largest city is Algiers, located in the far north on the Mediterranean coast. Inhabited since prehistory, Algeria has been at the crossroads of numerous cultures and civilisations, including the Phoenicians, Numidians, Ancient Rome, Romans, Vandals, and Byzantine Greeks. Its modern identity is rooted in centuries of Arab migrations to the Maghreb, Arab Muslim migration waves since Muslim conquest of the Maghreb, the seventh century and the subsequent Arabization, Arabisation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sahara Satellite Hires
The Sahara (, ) is a desert spanning across North Africa. With an area of , it is the largest hot desert in the world and the third-largest desert overall, smaller only than the deserts of Antarctica and the northern Arctic. The name "Sahara" is derived from , a broken plural form of ( ), meaning "desert". The desert covers much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and the Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south it is bounded by the Sahel, a belt of semi-arid tropical savanna around the Niger River valley and the Sudan region of sub-Saharan Africa. The Sahara can be divided into several regions, including the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Tén ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vegetation Africa
Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader than the term ''flora'' which refers to species composition. Perhaps the closest synonym is ''plant community'', but "vegetation" can, and often does, refer to a wider range of spatial scales than that term does, including scales as large as the global. Primeval redwood forests, coastal mangrove stands, sphagnum bogs, desert soil crusts, roadside weed patches, wheat fields, cultivated gardens and lawns; all are encompassed by the term "vegetation". The vegetation type is defined by characteristic dominant species, or a common aspect of the assemblage, such as an elevation range or environmental commonality. The contemporary use of "vegetation" approximates that of ecologist Frederic Clements' term '' earth cover'', a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North African Climate Cycles
North African climate cycles have a unique history that can be traced back millions of years. The cyclic climate pattern of the Sahara is characterized by significant shifts in the strength of the North African Monsoon. When the North African Monsoon is at its strongest, annual precipitation and consequently vegetation in the Sahara region increase, resulting in conditions commonly referred to as the " green Sahara". For a relatively weak North African Monsoon, the opposite is true, with decreased annual precipitation and less vegetation resulting in a phase of the Sahara climate cycle known as the "desert Sahara". Variations in the climate of the Sahara region can, at the simplest level, be attributed to the changes in insolation because of slow shifts in Earth's orbital parameters. The parameters include the precession of the equinoxes, obliquity, and eccentricity as put forth by the Milankovitch theory. The precession of the equinoxes is regarded as the most important orbital p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axial Tilt
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbital plane. It differs from orbital inclination. At an obliquity of 0 degrees, the two axes point in the same direction; that is, the rotational axis is perpendicular to the orbital plane. The rotational axis of Earth, for example, is the imaginary line that passes through both the North Pole and South Pole, whereas the Earth's orbital axis is the line perpendicular to the imaginary plane through which the Earth moves as it revolves around the Sun; the Earth's obliquity or axial tilt is the angle between these two lines. Over the course of an orbital period, the obliquity usually does not change considerably, and the orientation of the axis remains the same relative to the background of stars. This causes one pole to be pointed mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precession
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called '' nutation''. In physics, there are two types of precession: torque-free and torque-induced. In astronomy, ''precession'' refers to any of several slow changes in an astronomical body's rotational or orbital parameters. An important example is the steady change in the orientation of the axis of rotation of the Earth, known as the precession of the equinoxes. Torque-free or torque neglected Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Libyan Desert
The Libyan Desert (not to be confused with the Libyan Sahara) is a geographical region filling the northeastern Sahara Desert, from eastern Libya to the Western Desert (Egypt), Western Desert of Egypt and far northwestern Sudan. On medieval maps, its use predates today's Sahara, and parts of the Libyan Desert include the Sahara's most arid and least populated regions; this is chiefly what sets the Libyan Desert apart from the greater Sahara. The consequent absence of grazing, and near absence of waterholes or wells needed to sustain camel caravans, prevented Trans-Saharan trade between Kharga (the Darb al Arbein) close to the Nile, and Murzuk in the Libyan Fezzan. This obscurity saw the region overlooked by early European explorers, and it was not until the early 20th century and the advent of the motor car before the Libyan Desert started to be fully explored. Nomenclature The term ''Libyan Desert'' began to appear widely on European maps in the last decades of the 19th centu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ténéré
The Ténéré (Tuareg languages, Tuareg: Tenere, literally: "desert") is a desert region in south central Sahara. It comprises a vast plain of sand stretching from northeastern Niger to western Chad, occupying an area of over . The Ténéré's boundaries are said to be the Aïr Mountains in the west, the Hoggar Mountains in the north, the Djado Plateau in the northeast, the Tibesti Mountains in the east, and the basin of Lake Chad in the south. The central part of the desert, the Erg du Bilma, is centred at approximately . It is the locus of the Neolithic Tenerian culture. Name The name ''Ténéré'' comes from the Tuareg languages, Tuareg language, meaning "desert", in much the same way as the Arabic language, Arabic word for "desert", ''Sahara'', came to be applied to the region as a whole. Climate The Ténéré has a hot desert climate (Köppen climate classification ''BWh''), typical of the large Sahara Desert. The climate is hyper-arid, extremely hot, sunny and dry year-rou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aïr Mountains
The Aïr Mountains or Aïr Massif (Air Tamajeq language, Tamajăq: ''Ayǝr''; Hausa language, Hausa: Eastern ''Azbin'', Western ''Abzin'') is a triangular massif, located in northern Niger, within the Sahara. Part of the West Saharan montane xeric woodlands ecoregion, they rise to more than and extend over . Lying in the midst of desert north of the 17th parallel north, 17th parallel, the Aïr plateau, with an average altitude between , forms an island of Sahel climate which supports a wide variety of life, many pastoral and farming communities, and dramatic geological and archaeological sites. There are notable archaeological excavations in the region that illustrate the prehistoric past of this region. The endangered African wild dog (''Lycaon pictus'') once existed in this region, but may now be Local extinction, extirpated due to habitat fragmentation, human population pressures in this region. Geology The Precambrian to Cenozoic Aïr Mountains consist of p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tibesti Mountains
The Tibesti Mountains are a mountain range in the central Sahara, primarily located in the extreme north of Chad, with a small portion located in southern Libya. The highest peak in the range, Emi Koussi, lies to the south at a height of and is the highest point in both Chad and the Sahara. Bikku Bitti, the highest peak in Libya, is located in the north of the range. The central third of the Tibesti is of volcanic origin and consists of five volcanoes topped by large depressions: Emi Koussi, Tarso Toon, Tarso Voon, Tarso Yega and Toussidé. Major lava flows have formed vast plateaus that overlie Paleozoic sandstone. The volcanic activity was the result of a continental hotspot (geology), hotspot that arose during the Oligocene and continued in some places until the Holocene, creating fumaroles, hot springs, mud pools and deposits of natron and sulfur. Erosion has shaped volcanic spires and carved an extensive network of canyons through which run rivers subject to highly irregula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
