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Weathering of the chalk has created a characteristic soil known as rendzina. [7] Unlike many soils in which there are easily distinguished layers or soil horizons , a chalk rendzina soil consists of only a shallow dark humus rich surface layer which grades through a lighter brown hillwash containing small pellets of chalk, to the white of the ...
The Chalk Group is now divided into a White Chalk Subgroup and a Grey Chalk Subgroup, both of which are further subdivided into formations.These modern divisions replace numerous earlier divisions, references to which occur widely on geological maps and in other geological literature.
Chalk is a soft, white, porous, sedimentary carbonate rock.It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor.
Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.
Some are more resistant to weathering than the surrounding rock and stand up like walls, while others weather faster and form long narrow depressions. dip slope A geological formation often created by erosion of tilted strata. disconformity A surface that represents missing rock strata but beds above and below that surface are parallel to one ...
Residuum is weathered rock that is not transported by erosion, contributing in time to the formation of soil.It is distinguished from other types of parent material in that it is composed solely of mineral, not organic, material, and it remains in place rather than being moved by the action of wind, water, or gravity.
Like several of the thin limestones of the upper Greenhorn and lower Carlile, the Fencepost bed is a shell-rich, coccolithic, chalky limestone; however, this bed is hardened by a crystalline matrix of sparry concretory calcite so that it is more resistant to weathering and erosion. Unexposed, the Fencepost is olive-gray, weathering to light ...
Karst is not typically well developed in chalk, because chalk is highly porous rather than dense, so the flow of groundwater is not concentrated along fractures. Karst is also most strongly developed where the water table is relatively low, such as in uplands with entrenched valleys , and where rainfall is moderate to heavy.