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Cryoplanation
In geomorphology, cryoplanation or is a term used to both describe and explain the formation of plains, terraces and pediments in periglacial environments. Uncertainty surrounds the term, and the effectiveness of the cryoplanation process is held to be limited meaning it can only produce small terraces. Instead, many of so-called cryoplanation terraces are likely an expression of the underlying lithology and rock structure rather than being unique products of cold-climate processes. Cryoplanation can be seen as a variant of pediplanation that is restricted to cold climates. All the cryoplanation surfaces that exist at present date to the Quaternary. History of the concept The existence of flat bedrock surfaces in the mountains of Siberia was noted in the 1930s. Soviet scientists S.G. Boch and I.I. Krasnov first proposed a cyclical model for the formation these surfaces in 1943. This model influenced central and western European geomorphologists. Carl Troll, writing in Germa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycle Of Erosion
The geographic cycle, or cycle of erosion, is an idealized model that explains the development of relief in landscapes. The model starts with the erosion that follows uplift of land above a base level and ends, if conditions allow, in the formation of a peneplain. Landscapes that show evidence of more than one cycle of erosion are termed "polycyclical". The cycle of erosion and some of its associated concepts have, despite their popularity, been a subject of much criticism. Description William Morris Davis, the originator of the model, divided it into stages whose transition is gradual. The model begins with an uplifted or to-be-uplifted landscape. Then Davis defined a ''youthful'' stage where river incision is the dominant process shaping the landscape. During the ''youthful'' stage height, differences between uplands and valley bottoms increase rapidly. The ''youthful'' stage is followed by a ''mature'' stage in which height differences between valley bottoms and uplands are at t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lesotho Highlands
The Lesotho Highlands are formed by the Drakensberg and Maloti mountain ranges in the east and central parts of the country of Lesotho. Foothills form a divide between the lowlands and the highlands. Snow is common in the highlands in the winter. Location and description The Highlands are located to the southeast of the Highveld, encompassing the whole eastern part of Lesotho. The average annual rainfall is nearly 1,000 mm (40 inches) in some parts of the high ranges. Temperature is closely related to elevation in the Lesotho Highlands. In general, the mean July (winter) temperatures stay around 7 °C (45 °F). The Lesotho Highlands form a localized high spot on the Central Plateau of the Great Escarpment. This is because it is capped by a 1400 m thick layer of erosion resistant lava''Geological Map of South Africa, Lesotho and Swaziland''. (1970). Council for Geoscience, Geological Survey of South Africa. which welled up and spread across most of Southern A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planation Surface
In geology and geomorphology a planation surface is a large-scale surface that is almost flat with the possible exception of some residual hills. The processes that form planation surfaces are labelled collectively planation and are exogenic (chiefly erosion). Planation surfaces are planated regardless of bedrock structures. On Earth, they constitute some of the most common landscapes. Geological maps indicate that planation surfaces may comprise 65% of the landscapes on Saturn's largest moon, Titan, which hosts a hydrological cycle of liquid methane. Peneplains and pediplains are types of planation surfaces planated respectively by "peneplanation" and "pediplanation". In addition to these there are planation surfaces proposed to be formed by cryoplanation, marine processes, areal glacial erosion and salt weathering. The term ''planation surface'' is often preferred over others because some more specific planation surface types and processes remain controversial. Etchplains are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomorphology
Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform and terrain history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphologists work within disciplines such as physical geography, geology, geodesy, engineering geology, archaeology, climatology, and geotechnical engineering. This broad base of interests contributes to many research styles and interests within the field. Overview Earth's surface is modified by a combination of surface processes that shape landscapes, and geologic processes that cause tectonic uplift and subsidence, and shape the coastal geography. Surface processes co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomorphology (journal)
''Geomorphology'' is a peer-reviewed scientific journal about geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n .... External links * Earth and atmospheric sciences journals Elsevier academic journals English-language journals Geomorphology journals {{Geomorphology-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karoo-Ferrar
The Karoo and Ferrar Large Igneous Provinces (LIPs) are two large igneous provinces in Southern Africa and Antarctica respectively, collectively known as the Karoo-Ferrar, Gondwana,E.g. or Southeast African LIP, associated with the initial break-up of the Gondwana supercontinent at . Its flood basalt mostly covers South Africa and Antarctica but portions extend further into southern Africa and into South America, India, Australia and New Zealand. Karoo-Ferrar formed just prior to the breakup of Gondwana in the Lower Jurassic epoch, about 183 million years ago; this timing corresponds to the early Toarcian anoxic event and the Pliensbachian-Toarcian extinction. It covered about 3 x 106 km2. The total original volume of the flow, which extends over a distance in excess of 6000 km (4000 km in Antarctica alone), was in excess of 2.5 x 106 km³ (2.5 million cubic kilometres). The Ferrar LIP is notable for long distance transport and the Karoo LIP for its large volume and c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solifluction
Solifluction is a collective name for gradual processes in which a mass moves down a slope ("mass wasting") related to freeze-thaw activity. This is the standard modern meaning of solifluction, which differs from the original meaning given to it by Johan Gunnar Andersson in 1906. Origin and evolution of the concept In the original sense it meant the movement of waste saturated in water found in periglacial regions. However it was later discovered that various slow waste movements in periglacial regions did not require saturation in water, but were rather associated to freeze-thaw processes. The term solifluction was appropriated to refer to these slow processes, and therefore excludes rapid periglacial movements. In slow periglacial solifluction there are not clear gliding planes, and therefore skinflows and active layer detachments are not included in the concept. On the other hand, movement of waste saturated in water can occur in any humid climate, and therefore this kind of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blockfield
A blockfieldWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984, pp. 66 and 190. . (also spelt block fieldLeser, Hartmut, ed. (2005). ''Wörterbuch Allgemeine Geographie'', 13th ed., dtv, Munich, pp. 107 and 221. . ), felsenmeer, boulder field or stone field is a surface covered by boulder- or block-sized angular rocks usually associated with alpine and subpolar climates and periglaciation. Blockfields differ from screes and talus slope in that blockfields do not apparently originate from mass wastings. They are believed to be formed by frost weathering below the surface. An alternative theory that modern blockfields may have originated from chemical weathering that occurred in the Neogene when the climate was relatively warmer. Following this thought the blockfields would then have been reworked by periglacial action. Most known blockfields are located in the northern hemisphere. Examples can be found in Abisko National Park in Sweden, Snowdonia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frost Weathering
Frost weathering is a collective term for several mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes such as frost shattering, frost wedging and cryofracturing. The process may act on a wide range of spatial and temporal scales, from minutes to years and from dislodging mineral grains to fracturing boulders. It is most pronounced in high-altitude and high-latitude areas and is especially associated with alpine, periglacial, subpolar maritime and polar climates, but may occur anywhere at sub-freezing temperatures (between -3 and -8 °C) if water is present. Ice segregation Certain frost-susceptible soils expand or heave upon freezing as a result of water migrating via capillary action to grow ice lenses near the freezing front. This same phenomenon occurs within pore spaces of rocks. The ice accumulations grow larger as they attract liquid water from the surrounding ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regolith
Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestrial planets and moons. Etymology The term ''regolith'' combines two Greek words: (), 'blanket', and (), 'rock'. The American geologist George P. Merrill first defined the term in 1897, writing: Earth Earth's regolith includes the following subdivisions and components: * soil or pedolith * alluvium and other transported cover, including that transported by aeolian, glacial, marine, and gravity flow processes. * "saprolith'", generally divided into the ** ''upper saprolite'': completely oxidised bedrock ** ''lower saprolite'': chemically reduced partially weathered rocks ** ''saprock'': fractured bedrock with weathering restricted to fracture margins * volcanic ash and lava flows that are interbedded with unconsolidated material * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface is underlain by permafrost, with the total area of around 18 million km2. This includes substantial areas of Alaska, Greenland, Canada and Siberia. It can also be located on mountaintops in the Southern Hemisphere and beneath ice-free areas in the Antarctic. Permafrost does not have to be the first layer that is on the ground. It can be from an inch to several miles deep under the Earth's surface. It frequently occurs in ground ice, but it can also be present in non-porous bedrock. Permafrost is formed from ice holding various types of soil, sand, and rock in combination. Permafrost contains large amounts of biomass and decomposed biomass that has been stored as methane and carbon dioxide, making tundra soil a carbon sink. As global war ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., it borders the Canadian province of British Columbia and the Yukon territory to the east; it also shares a maritime border with the Russian Federation's Chukotka Autonomous Okrug to the west, just across the Bering Strait. To the north are the Chukchi and Beaufort Seas of the Arctic Ocean, while the Pacific Ocean lies to the south and southwest. Alaska is by far the largest U.S. state by area, comprising more total area than the next three largest states (Texas, California, and Montana) combined. It represents the seventh-largest subnational division in the world. It is the third-least populous and the most sparsely populated state, but by far the continent's most populous territory located mostly north of the 60th parallel, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
