|
Aggradation
Aggradation (or alluviation) is the term used in geology for the increase in land elevation, typically in a river system, due to the deposition of sediment. Aggradation occurs in areas in which the supply of sediment is greater than the amount of material that the system is able to transport. The mass balance between sediment being transported and sediment in the bed is described by the Exner equation. Typical aggradational environments include lowland alluvial rivers, river deltas, and alluvial fans. Aggradational environments are often undergoing slow subsidence which balances the increase in land surface elevation due to aggradation. After millions of years, an aggradational environment will become a sedimentary basin, which contains the deposited sediment, including paleochannels and ancient floodplains. Aggradation can be caused by changes in climate, land use, and geologic activity, such as volcanic eruption, earthquake An earthquakealso called a quake, tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exner Equation
The Exner equation describes conservation of mass between sediment in the bed of a channel and sediment that is being transported. It states that bed elevation increases (the bed aggrades) proportionally to the amount of sediment that drops out of transport, and conversely decreases (the bed degrades) proportionally to the amount of sediment that becomes entrained by the flow. It was developed by the Austrian meteorologist and sedimentologist Felix Maria Exner, from whom it derives its name. It is typically applied to sediment in a fluvial system such as a river. The Exner equation states that the change in bed elevation, \eta, over time, t, is equal to one over the grain packing density, \varepsilon_o, times the negative divergence of sediment flux, \mathbf, : \frac = -\frac\nabla\cdot\mathbf Note that \varepsilon_o can also be expressed as (1-\lambda_p), where \lambda_p equals the bed porosity. Good values of \varepsilon_o for natural systems range from 0.45 to 0.75.Pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleochannel
In the Earth sciences, a palaeochannel, also spelled paleochannel, is a significant length of a river or stream channel which no longer conveys fluvial discharge as part of an active fluvial system. The term ''palaeochannel'' is derived from the combination of two words, ''palaeo'' or ''old'', and '' channel''; i.e., a palaeochannel is an old channel. Palaeochannels may be preserved either as abandoned surface channels on the surface of river floodplains and terraces or infilled and partially or fully buried by younger sediments. The fill of a palaeochannel and its enclosing sedimentary deposits may consist of unconsolidated, semi-consolidated, or well-cemented sedimentary strata depending on the action of tectonics and diagenesis during their geologic history after deposition. The abandonment of an active fluvial channel and the resulting formation of a palaeochannel can be the result of tectonic processes, geomorphologic processes, anthropogenic activities, climatic changes, o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Delta
A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creation of a river delta occurs at the '' river mouth'', where the river merges into an ocean, a sea, or an estuary, into a lake, a reservoir, or (more rarely) into another river that cannot carry away the sediment supplied by the feeding river. Etymologically, the term ''river delta'' derives from the triangular shape (Δ) of the uppercase Greek letter delta. In hydrology, the dimensions of a river delta are determined by the balance between the watershed processes that supply sediment and the watershed processes that redistribute, sequester, and export the supplied sediment into the receiving basin. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrology), discharge.Goudie, A. S., 2004, ''Encyclopedia of Geomorphology'', vol. 1. Routledge, New York. The soils usually consist of clays, silts, sands, and gravels deposited during floods. Because of regular flooding, floodplains frequently have high soil fertility since nutrients are deposited with the flood waters. This can encourage farming; some important agricultural regions, such as the Nile and Mississippi Basin, Mississippi Drainage basin, river basins, heavily exploit floodplains. Agricultural and urban regions have developed near or on floodplains to take advantage of the rich soil and freshwater. However, the Flood risk, risk of inundation has led to increasing efforts to Flood control, control flooding. Formation Most floodplai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alluvial
Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is typically geologically young and is not consolidated into solid rock. Sediments deposited underwater, in seas, estuaries, lakes, or ponds, are not described as alluvium. Floodplain alluvium can be highly fertile, and supported some of the earliest human civilizations. Definitions The present consensus is that "alluvium" refers to loose sediments of all types deposited by running water in floodplains or in alluvial fans or related landforms. However, the meaning of the term has varied considerably since it was first defined in the French dictionary of Antoine Furetière, posthumously published in 1690. Drawing upon concepts from Roman law, Furetière defined '' alluvion'' (the French term for alluvium) as new land formed by deposition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Eruption
A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three main types of volcanic eruptions. Magmatic eruptions involve the decompression of gas within magma that propels it forward. Phreatic eruptions are driven by the superheating of steam due to the close proximity of magma. This type exhibits no magmatic release, instead causing the granulation of existing rock. Phreatomagmatic eruptions are driven by the direct interaction of magma and water, as opposed to phreatic eruptions, where no fresh magma reaches the surface. Within these broad eruptive types are several subtypes. The we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomorphology
Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated 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 comprise the action of water, wind, ice, wildfire, and lif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Mohrig
David Mohrig is an American professor of geology and geomorphology whose works have been published in such journals as the Geological Society of America Bulletin, Journal of Hydraulic Engineering and many others. Currently he works at Jackson School of Geosciences of Austin, Texas Austin ( ) is the List of capitals in the United States, capital city of the U.S. state of Texas. It is the county seat and most populous city of Travis County, Texas, Travis County, with portions extending into Hays County, Texas, Hays and W .... References External linksDavid Mohrig Living people 20th-century births American geologists Year of birth missing (living people) Place of birth missing (living people) {{US-geologist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BBC News Online
BBC News Online is the website of BBC News, the division of the BBC responsible for newsgathering and production. It is one of the most popular news websites, with 1.2 billion website visits in April 2021, as well as being used by 60% of the UK's internet users for news. The website contains international news coverage, as well as British, entertainment, science, and political news. Many reports are accompanied by audio and video from the BBC's BBC Television, television and BBC Radio, radio news services, while the latest TV and radio bulletins are also available to view or listen to on the site together with other current affairs programmes. BBC News Online is closely linked to its sister department website, that of BBC Sport. Both sites follow similar layout and content options and respective journalists work alongside each other. Location information provided by users is also shared with the website of BBC Weather to provide local content. From 1998 to 2001 the site was n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature Geoscience
''Nature Geoscience'' is a monthly peer-reviewed scientific journal published by the Nature Publishing Group. The Chief Editor is Tamara Goldin, who took over from Heike Langenberg in February 2020. It was established in January 2008. Scope The journal covers all aspects of the Earth sciences, including theoretical research, modelling, and field work. Significant related work in other fields, such as atmospheric sciences, geology, geophysics, climatology, oceanography, palaeontology, and space science, is also published. Abstracting and indexing The journal is abstracted and indexed by: * '' CAB Abstracts'' * ''Chemical Abstracts Service/ CASSI'' * ''Science Citation Index'' * ''Current Contents/Physical, Chemical & Earth Sciences'' * '' GeoRef'' According to the ''Journal Citation Reports'', the journal has a 2020 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a type of journal ranking. Journals with higher impact f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Colorado At Boulder
The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a Public university, public research university in Boulder, Colorado, United States. Founded in 1876, five months before Colorado became a Federated state, state, it is the flagship university of the University of Colorado system. CU Boulder is a member of the Association of American Universities, considered a Public Ivy and is Carnegie Classification of Institutions of Higher Education, classified among R1: Doctoral Universities – Very high research activity. The university consists of nine colleges and schools and offers over 150 academic programs, enrolling more than 35,000 students as of January 2022. In 2021, the university attracted the support of over $634 million for research and spent $536 million on research and development according to the National Science Foundation, ranking it 50th in the nation. It receives the most NASA astrophysics technology grants of all academic institutions and is the only ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
