A water gap is an opening or notch which flowing water has carved through a mountain range. Water gaps often offer a practical route for road and rail transport to cross mountain ridges.
A water gap is usually an indication of a river that is older than the current topography. The river likely established its course when the landform was at a low elevation, with a very low stream gradient and a thick layer of unconsolidated sediment. The river therefore established its channel without regard for the deeper layers of rock. A later period of uplift caused increased erosion along the riverbed, exposing the underlying rock layers. As the uplift continued, the river, being large enough, continued to erode the rising land, cutting through ridges as they formed.
Water gaps are common in the ridge-and-valley Appalachians of eastern North America.
Alternatively, a water gap can be formed through headward erosion of two streams on opposite sides of a ridge, ultimately resulting in the capture of one stream by the other.
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state (water vapor or steam). Water also exists in a liquid crystal state near hydrophilic surfaces. Under nomenclature used to name chemical compounds, dihydrogen monoxide is the scientific name for water, though it is almost never used.
Water covers 70.9% of the Earth's surface, and is vital for all known forms of life. On Earth, 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.
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Gap or The Gap may refer to:
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