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The origin of water on Earth is the subject of a body of research in the fields of planetary science, astronomy, and astrobiology. Earth is unique among the rocky planets in the Solar System in having oceans of liquid water on its surface. [ 2] Liquid water, which is necessary for all known forms of life, continues to exist on the surface of ...
Water pollution in the United States is a growing problem that became critical in the 19th century with the development of mechanized agriculture, mining, and industry, although laws and regulations introduced in the late 20th century have improved water quality in many water bodies. [ 1] Extensive industrialization and rapid urban growth ...
The history of agriculture in the United States covers the period from the first English settlers to the present day. In Colonial America, agriculture was the primary livelihood for 90% of the population, and most towns were shipping points for the export of agricultural products. Most farms were geared toward subsistence production for family use.
Quizlet is a multi-national American company that provides tools for studying and learning. [ 1] Quizlet was founded in October 2005 by Andrew Sutherland, who at the time was a 15-year old student, [ 2] and released to the public in January 2007. [ 3] Quizlet's primary products include digital flash cards, matching games, practice electronic ...
The Ogallala Aquifer (oh-gə-LAH-lə) is a shallow water table aquifer surrounded by sand, silt, clay, and gravel located beneath the Great Plains in the United States. As one of the world's largest aquifers, it underlies an area of approximately 174,000 sq mi (450,000 km 2) in portions of eight states (South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas). [1]
In New York, the medical department of King's College was established in 1767, and in 1770, awarded the first American M.D. degree. [ 13] Smallpox inoculation was introduced 1716–1766, well before it was accepted in Europe. The first medical schools were established in Philadelphia in 1765 and New York in 1768.
This recession was one of the main causes of the American Civil War, which would begin in 1861 and end in 1865. This is the earliest recession to which the NBER assigns specific months (rather than years) for the peak and trough. [ 6][ 8][ 21] 1860–1861 recession. October 1860 – June 1861. 8 months.
Water falling as rain upstream of the reservoir, together with any groundwater emerging as springs, is stored in the reservoir. Any excess water can be spilled via a specifically designed spillway. Stored water may be piped by gravity for use as drinking water, to generate hydro-electricity or to maintain river flows to support downstream uses ...