|
Hamada (other)
A hamada (, ) is a type of desert landscape consisting of high, largely barren, hard rocky ( basalt) plateaus, where most of the sand has been removed by deflation. The majority of the Sahara is hamada. Other examples are Negev desert in PLASTEAN and the in Algeria. Formation Hamadas are produced by the wind, which removes the fine products of weathering, an aeolian process known as deflation. The finer-grained products are taken away in suspension. At the same time, the sand is removed through saltation and surface creep, leaving behind a landscape of gravel, boulders and bare rock. Related landforms Hamada is related to desert pavement (known variously as reg, serir, gibber, or saï), which occurs as stony plains or depressions covered with gravels or boulders rather than as highland plateaus. Hamadas exist in contrast to '' ergs'', which are large areas of shifting sand dune A dune is a landform composed of wind- or water-driven sand. It typically take ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
La Hamada Noire Du Tademayt 1890
LA most frequently refers to Los Angeles, the second largest city in the United States. La, LA, or L.A. may also refer to: Arts and entertainment Music * La (musical note), or A, the sixth note * "L.A.", a song by Elliott Smith on ''Figure 8'' (album) * ''L.A.'' (EP), by Teddy Thompson * ''L.A. (Light Album)'', a Beach Boys album * "L.A." (Neil Young song), 1973 * The La's, an English rock band * L.A. Reid, a prominent music producer * Yung L.A., a rapper * Lady A, an American country music trio * "L.A." (Amy Macdonald song), 2007 * "La", a song by Australian-Israeli singer-songwriter Old Man River Other media * l(a, a poem by E. E. Cummings * La (Tarzan), fictional queen of the lost city of Opar (Tarzan) * ''Lá'', later known as Lá Nua, an Irish language newspaper * La7, an Italian television channel * LucasArts, an American video game developer and publisher * Liber Annuus, academic journal Business, organizations, and government agencies * L.A. Screenings, a tel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saltation (geology)
In geology, saltation () is a specific type of particle transport by fluids such as wind or water. It occurs when loose materials are removed from a bed and carried by the fluid, before being transported back to the surface. Examples include pebble transport by rivers, sand drift over desert surfaces, soil blowing over fields, and snow drift over smooth surfaces such as those in the Arctic or Canadian Prairies. Process At low fluid velocities, loose material rolls downstream, staying in contact with the surface. This is called ''creep'' or ''reptation''. Here the forces exerted by the fluid on the particle are only enough to roll the particle around the point of contact with the surface. Once the wind speed reaches a certain critical value, termed the ''impact'' or ''fluid threshold'', the drag and lift forces exerted by the fluid are sufficient to lift some particles from the surface. These particles are accelerated by the fluid, and pulled downward by gravity, causing them to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amaranthaceae
Amaranthaceae is a family of flowering plants commonly known as the amaranth family, in reference to its type genus ''Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, making it the most species-rich lineage within its parent order, Caryophyllales. Description Vegetative characters Most species in the Amaranthaceae are annual or perennial herbs or subshrubs; others are shrubs; very few species are vines or trees. Some species are succulent. Many species have stems with thickened nodes. The wood of the perennial stem has a typical "anomalous" secondary growth; only in subfamily Polycnemoideae is secondary growth normal. The leaves are simple and mostly alternate, sometimes opposite. They never possess stipules. They are flat or terete, and their shape is extremely variable, with entire or toothed margins. In some species, the leaves are reduced to minute scales. In most cases, neither basal nor terminal aggrega ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hammada (plant)
''Hammada'' is a genus of flowering plants belonging to the family Amaranthaceae. It is also in the Salsoloideae subfamily. Although it is a very unclear and unsorted genus with many species that have later been classed as synonyms. Its native range is Central Asia and is found in Iraq, Lebanon, Palestine, Syria, Turkey and Uzbekistan. They are often found growing in alkaline or saline habitats. Description They are perennial plants, with a glabrous (smooth) wood (only at the base). They can grow up to tall.Michael Zohary The weed-like plants have regular, minute, or small, cyclic flowers. The flowers have no petals, but 5 sepals which are united at the base. It has 5 stamens and the ovary is positioned superior and consists of 2 united carpels. Which late matures into a fruit (or seed capsule). Known species According to Plants of the World Online; * ''Hammada eriantha'' Botsch. (from Uzbekistan) * ''Hammada ramosissima'' (Boiss. ex Eig) Iljin (from Iraq, Lebanon, Palestine, S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sand Dune
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat regions covered with wind-swept sand or dunes with little or no vegetation are called ''ergs'' or ''sand seas''. Dunes occur in different shapes and sizes, but most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter ''slip face'' in the lee side. The valley or trough between dunes is called a ''dune slack''. Dunes are most common in desert environments, where the lack of moisture hinders the growth of vegetation that would otherwise interfere with the development of dunes. However, sand deposits are not restricted to deserts, and dunes are also found along sea shores, along streams in semiarid climates, in areas of glacial outwash, and in other areas where poorly cemented san ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erg (landform)
An erg (also sand sea or dune sea, or sand sheet if it lacks dunes) is a broad, flat area of desert covered with wind-swept sand with little or no vegetative cover. The word is derived from the Arabic word ''ʿarq'' (), meaning "dune field". Strictly speaking, an erg is defined as a desert area that contains more than of aeolian or wind-blown sand and where sand covers more than 20% of the surface. Smaller areas are known as "dune fields". The largest hot desert in the world, the Sahara, covers and contains several ergs, such as the Chech Erg and the Issaouane Erg in Algeria. Approximately 85% of all the Earth's mobile sand is found in ergs that are greater than . Ergs are also found on other celestial bodies, such as Venus, Mars, and Saturn's moon Titan. Description Ergs are concentrated in two broad belts between 20° to 40°N and 20° to 40°S latitudes, which include regions crossed by the dry, subsiding air of the trade winds. Active ergs are limited to regions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desert Pavement
A desert pavement, also called reg (in the western Sahara), serir (eastern Sahara), gibber (in Australia), or saï (central Asia) is a desert surface covered with closely packed, interlocking angular or rounded rock fragments of pebble and cobble size. They typically top alluvial fans. Desert varnish collects on the exposed surface rocks over time. Geologists debate the mechanics of pavement formation and their age. Formation Several theories have been proposed for the formation of desert pavements. A common theory suggests that they form through the gradual removal of sand, dust and other fine-grained material by the wind and intermittent rain, leaving the larger fragments behind. The larger fragments are shaken into place through the forces of rain, running water, wind, gravity, creep, thermal expansion and contraction, wetting and drying, frost heaving, animal traffic, and the Earth's constant microseismic vibrations. The removal of small particles by wind does not conti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boulder
In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In common usage, a boulder is too large for a person to move. Smaller boulders are usually just called rocks or stones. The word ''boulder'' derives from ''boulder stone'', from the Middle English ''bulderston'' or Swedish ''bullersten''. Online Etymology Dictionary. Retrieved December 9, 2011, from Dictionary.com website. In places covered by s during s, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
