Search results
Results from the WOW.Com Content Network
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains, cemented together by another mineral. Sandstones comprise about 20–25% of all sedimentary rocks. [1] Most sandstone is composed of quartz or feldspar, because they are the most resistant minerals to the weathering processes at the Earth's ...
Rock shelters form because a rock stratum such as sandstone that is resistant to erosion and weathering has formed a cliff or bluff, but a softer stratum, more subject to erosion and weathering, lies just below the resistant stratum, and thus undercuts the cliff.
Sandstone is bedded, which provides zones of weakness, along which weathering and erosion takes place. Iron oxide and calcium carbonate cemented sandstones produce fins. [1] These are typically seen as weak cements, compared to the erosion resistant silica cement, but in arid and semi-arid regions they are much more resistant.
The Shinarump Conglomerate is a highly resistant coarse-grained sandstone and pebble conglomerate [1] (minor or major conglomerates are a typical base layer after unconformities or disconformities; the Shinarump is a major conglomerate) with rare lenses of mudstone, sometimes forming a caprock because of its hardness, cementation, and erosion resistance. [2]
The Tapeats Sandstone is about 70 m (230 ft) thick, at its maximum. The lower and middle sandstone beds of the Tapeats Sandstone are well-cemented, resistant to erosion, and form brownish, vertical cliffs that rise above the underlying Precambrian strata outcropping within Granite Gorge (Inner Gorge). They form the edge of the Tonto Platform.
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.
The Coldwater Sandstone (or Coldwater Formation) is a sedimentary geologic unit of Eocene age found in Southern California, primarily in and south of the Santa Ynez Mountains of Santa Barbara County, and east into Ventura County. It consists primarily of massive arkosic sandstone with some siltstone and shale. Being exceptionally resistant to ...
The precipitation of iron oxides also formed laminae, corrugated layers, columns, and pipes of ironstone within the Navajo Sandstone. Being harder and more resistant to erosion than the surrounding sandstone, the ironstone weathered out as ledges, walls, fins, "flags", towers, and other minor features, which stick out and above the local ...