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Superficial deposits (or surficial deposits [1]) refer to geological deposits typically of Quaternary age (less than 2.6 million years old) for the Earth. These geologically recent unconsolidated sediments may include stream channel and floodplain deposits, beach sands, talus gravels and glacial drift and moraine.
Erosion on Koh Tao Island. Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, sheetwash, slow continuous downslope creep, or a variable combination of these processes.
In 1839, geologist Roderick Murchison [3] introduced the term drift to describe unconsolidated surficial sediments previously called diluvium.The term drift refers to the drift hypothesis proposed by Charles Lyell, [4] as influenced by contemporary polar research, that these sediments had been transported by sea ice and icebergs drifting in marine currents.
Valley colluvium refers to the loose, unconsolidated sediments that have been settled inside the water courses and are driven by river mechanisms. [1] They are thin in shape and extended into straight lines that follow the river channels. [1] The plants grown on the valley colluvium are thicker than the nearby areas. [1]
Glacial till is mostly derived from subglacial erosion and from the entrainment by the moving ice of previously available unconsolidated sediments. Bedrock can be eroded through the action of glacial plucking and abrasion , and the resulting clasts of various sizes will be incorporated to the glacier's bed.
Commonly found on unconsolidated river and beach sediments of sand and clay or volcanic ash, some have an A horizon on top of bedrock. They are 18% of soils worldwide. Gelisol – permafrost soils with permafrost within two metres of the surface or gelic materials and permafrost within one metre. They constitute 9% of soils worldwide.
Parent material is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are often classified based upon their contents of consolidated or unconsolidated mineral material that has undergone some degree of physical or chemical ...
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.