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Alluvial fans are common in the geologic record, such as in the Triassic basins of eastern North America and the New Red Sandstone of south Devon. Such fan deposits likely contain the largest accumulations of gravel in the geologic record. Alluvial fans have also been found on Mars and Titan, showing that fluvial processes have occurred on ...
Abyssal (or submarine) fans are formed from turbidity currents. These currents begin when a geologic activity pushes sediments over the edge of a continental shelf and down the continental slope, creating an underwater landslide. A dense slurry of muds and sands speeds towards the foot of the slope, until the current slows. The decreasing ...
Also called Indianite. A mineral from the lime-rich end of the plagioclase group of minerals. Anorthites are usually silicates of calcium and aluminium occurring in some basic igneous rocks, typically those produced by the contact metamorphism of impure calcareous sediments. anticline An arched fold in which the layers usually dip away from the fold axis. Contrast syncline. aphanic Having the ...
Alluvial or sedimentary fans are shallow cone-shaped reliefs at the base of the continental slope that merge together, forming the continental rise. [2] Erosional submarine canyons slope downward and lead to alluvial fan valleys with increasing depth. [2] It is in this zone that sediment is deposited, forming the continental rise.
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. [1] [7] [8] 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.
A subaqueous fan is a fan-shaped deposit formed beneath water (similar to deltas or terrestrial alluvial fans), that is commonly related to glaciers [1] and crater lakes. [ 2 ] Subaqueous fan deposits are generally described as coarse to fine gravel and/or sand , with variable texture and sorting.
They make up significant percentages of many alluvial fans and debris cones along steep mountain fronts. Fully exposed deposits commonly have lobate forms with boulder-rich snouts, and the lateral margins of debris-flow deposits and paths are commonly marked by the presence of boulder-rich lateral levees .
In this arid environment, alluvial fans form at the mouth of these streams. Very large alluvial fans merged to form continuous alluvial slopes called bajadas along the Panamint Range. [33] The faster uplift along the Black Mountains formed much smaller alluvial fans because older fans are buried under playa sediments before they can grow too large.