|
Bedrock River
A bedrock river is a river that has little to no alluvium mantling the bedrock over which it flows. However, most bedrock rivers are not pure forms; they are a combination of a bedrock channel and an alluvial channel. The way one can distinguish between bedrock rivers and alluvial rivers is through the extent of sediment cover. The extent of sediment coverage is based upon the sediment flux supplied to the channel and the channel transport capacity. Bedrock rivers are typically found in upland or mountainous regions. Their formation can have several erosional factors. Bedrock rivers are also one of the only ways to study incision into bedrock that is not related to glaciers. Forming and erosion Bedrock incision can be caused by tectonic plate movement. As the land is uplifted the river is forced to incise into the bedrock to keep flowing. Incision can be carried out through a variety of erosional processes. The type of bedrock may change as a river flows downstream, affecting ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giba Near Gabat
Gilberto Amauri de Godoy Filho (), known as Giba (; born 23 December 1976), is a Brazilian former professional volleyball player who played as an outside hitter. For much of the 2000s, he was widely regarded as one of the best volleyball players in the world. During his professional career he played in Brazil, Italy, Russia, Argentina and briefly in the United Arab Emirates. He is mostly remembered for his successes with the national team. With the Brazilian National Team he won a total of 8 South American Championships, 3 America's Cups, 8 World League titles, 3 World Grand Champions Cups, three World Championships (2002, 2006, 2010), a gold medal at the 2004 Summer Olympics and two silver medals at the 2008 and 2012 Summer Olympics, where he was the team's captain. During summer 2014, Giba retired from professional volleyball at the age of 37. Club career Giba debuted in his country for clubs such as Curitibano, Cocamar, Chapecó, São Caetano, Nipomed, Olympikus and M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grade (slope)
The grade (US) or gradient (UK) (also called stepth, slope, incline, mainfall, pitch or rise) of a physical feature, landform or constructed line is either the elevation angle of that surface to the horizontal plane, horizontal or its tangent. It is a special case of the slope, where zero indicates horizontal plane, horizontality. A larger number indicates higher or steeper degree of "tilt". Often slope is calculated as a ratio of "rise" to "run", or as a fraction ("rise over run") in which ''run'' is the horizontal distance (not the distance along the slope) and ''rise'' is the vertical distance. Slopes of existing physical features such as canyons and hillsides, bank (geography), stream and river banks, and stream bed, beds are often described as grades, but typically the word "grade" is used for human-made surfaces such as roads, landscape grading, roof pitches, rail tracks, railroads, aqueduct (watercourse), aqueducts, and pedestrian or bicycle routes. The grade may refer to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbonate Rock
Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and Dolomite (rock), dolomite rock (also known as dolostone), which is composed of Dolomite (mineral), dolomite (CaMg(CO3)2). They are usually Dunham classification, classified on the basis of texture and grain size. Importantly, carbonate rocks can exist as metamorphic and igneous rocks, too. When recrystallized carbonate rocks are Metamorphic rock, metamorphosed, marble is created. Rare igneous rock, igneous carbonate rocks even exist as Intrusive rock, intrusive carbonatites and, even rarer, there exists volcanic carbonate lava. Carbonate rocks are also crucial components to understanding Geological history of Earth, geologic history due to processes such as diagenesis in which carbonates undergo compositional changes based on kinetic effects. The correlation between this compo ... [...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] |
Headward Erosion
Headward erosion is erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, lengthening the stream channel.Essentials of Geology, 3rd Ed, Stephen Marshak It can also refer to the widening of a canyon by erosion along its very top edge, when sheets of water first enter the canyon from a more roughly planar surface above it, such as at Canyonlands National Park in Utah. When sheets of water on a roughly planar surface first enter a depression in it, this erodes the top edge of the depression. The stream is forced to grow longer at the very top of the stream, which moves its origin back, or causes the canyon formed by the stream to grow wider as the process repeats. Widening of the canyon by erosion inside the canyon, below the canyon side top edge, or origin or the stream, such as erosion caused by the streamflow inside it, is not called headward erosion. Headward erosion is a fluvial process of erosion that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shear Stress
Shear stress (often denoted by , Greek alphabet, Greek: tau) is the component of stress (physics), stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the other hand, arises from the force vector component perpendicular to the material cross section on which it acts. General shear stress The formula to calculate average shear stress or force per unit area is: \tau = ,where is the force applied and is the cross-sectional area. The area involved corresponds to the material face (geometry), face parallel to the applied force vector, i.e., with surface normal vector perpendicular to the force. Other forms Wall shear stress Wall shear stress expresses the retarding force (per unit area) from a wall in the layers of a fluid flowing next to the wall. It is defined as:\tau_w := \mu\left.\frac\_,where is the dynamic viscosity, is the flow velocity, and is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traction (geology)
Traction is the geologic Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth s ... process whereby a current transports larger, heavier rocks by rolling or sliding them along the bottom. Thus, the grains and clasts interact with the substratum during transport. By contrast, saltation, a related sediment transport process, moves grains across the bottom by bouncing or hopping. The actual current carries the sediment load in traction and saltation flows, whereas downslope movement under the force of gravity carries the sediment in gravity flows. These processes contrast with suspension settling, in which there is no current.Ritter, M.E. (2006), The Physical Environment: an Introduction to Physical Geography: The Geologic Work of Streams,'' online textbook. accessed 25 June 2013. Traction is ... [...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 t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bed Load
The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load. Bed load moves by rolling, sliding, and/or Saltation (geology), saltating (hopping). Generally, bed load downstream will be smaller and more rounded than bed load upstream (a process known as downstream fining). This is due in part to Wear, attrition and Abrasion (geology), abrasion which results from the stones colliding with each other and against the river channel, thus removing the rough texture (Rounding (sediment), rounding) and reducing the size of the particles. However, selective transport of sediments also plays a role in relation to downstream fining: smaller-than average particles are more easily Entrainment (physical geography), entrained than larger-than average particles, since the shear stress required to entrain a grain is linearly proportional to the diameter of the grain. Howev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suspended Load
The suspended load of a flow of fluid, such as a river, is the portion of its sediment uplifted by the fluid's flow in the process of sediment transportation. It is kept suspended by the fluid's turbulence. The suspended load generally consists of smaller particles, like clay, silt, and fine sands''.'' Sediment transportation The suspended load is one of the three layers of the fluvial sediment transportation system. The bed load consists of the larger sediment which is transported by saltation, rolling, and dragging on the riverbed. The suspended load is the middle layer that consists of the smaller sediment that's suspended. The wash load is uppermost layer which consist of the smallest sediment that can be seen with the naked eye; however, the wash load gets easily mixed with suspended load during transportation due to the very similar process. The wash load never touches the bed even outside of a current. Composition The boundary between bed load and suspended l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissolved Load
Dissolved load is the portion of a stream's total sediment load that is carried in solution, especially ions from chemical weathering. It is a major contributor to the total amount of material removed from a river's drainage basin, along with suspended load and bed load. The amount of material carried as dissolved load is typically much smaller than the suspended load, though this is not always the case, particularly when the available river flow is mostly harnessed for purposes such as irrigation or industrial uses. Dissolved load comprises a significant portion of the total material flux out of a landscape, and its composition is important in regulating the chemistry and biology of the stream water. The dissolved load is primarily controlled by the rate of chemical weathering, which depends on climate and weather conditions such as moisture and temperature. Dissolved load has many useful applications within the field of geology, including erosion, denudation, and reconstructi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluvial
A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it runs out of water, or only flow during certain seasons. Rivers are regulated by the water cycle, the processes by which water moves around the Earth. Water first enters rivers through precipitation, whether from rainfall, the runoff of water down a slope, the melting of glaciers or snow, or seepage from aquifers beneath the surface of the Earth. Rivers flow in channeled watercourses and merge in confluences to form drainage basins, or catchments, areas where surface water eventually flows to a common outlet. Rivers have a great effect on the landscape around them. They may regularly overflow their banks and flood the surrounding area, spreading nutrients to the surrounding area. Sediment or alluvium carried by rivers shapes the landscape a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
