Pub. date: 2008 | Online Pub. Date: April 25, 2008 | DOI: 10.4135/9781412963893 | Print ISBN: 9781412958783 | Online ISBN: 9781412963893 | Publisher:SAGE Publications, Inc.About this encyclopedia
Velma I. Grover
ALL LIFE ON Earth exists within a thin film of air, water, and soil about 9.3 mi. (15 km.) deep. This spherical shell of life is known as the biosphere. The biosphere can be divided into three layers: the atmosphere (air), the hydrosphere (water), and the lithosphère (rock and soil). The unique attributes of the Earth's atmosphere create a habitable place for humans, animals, and plants. It reaches over 348 mi. (560 km.) from the surface of the Earth. The atmosphere is a mixture of gases and particles that surround the planet. When seen from space, the atmosphere appears as a thin seam of dark blue light on a curved horizon. It is made of layers that surround the Earth like rings. About 99 percent of the Earths atmosphere occurs within 31 mi. (50 km.) above the surface. The remaining one percent extends outward for several hundred km., fading The ...