Earth science generally recognizes four spheres, the lithosphere, the hydrosphere, the atmosphere, and the See more

The Earth's crust, or lithosphere, is the outermost solid surface of the planet and is chemically and mechanically different from underlying mantle. It has been generated greatly by igneous processes in which magma cools … See more

Most water is found in various kinds of natural body of water.
An ocean is a major body of saline water, and a component of the hydrosphere. Approximately 71% of the surface of the Earth (an … See more

The atmosphere of the Earth serves as a key factor in sustaining the planetary ecosystem. The thin layer of gases that envelops the Earth is held in place by the planet's gravity. Dry air consists of 78% nitrogen, … See more

Evidence suggests that life on Earth has existed for about 3.7 billion years. All known life forms share fundamental molecular mechanisms, and based on these observations, theories on the origin of life attempt to f… See more

An ecosystem (also called an environment) is a natural unit consisting of all plants, animals, and micro-organisms (biotic factors) in an area functioning together with all of the non-living physical (abiotic) factors of the envir… See more

Global biogeochemical cycles are critical to life, most notably those of water, oxygen, carbon, nitrogen and phosphorus.
• The nitrogen cycle is the transformation of nitrogen and nitrogen-containing compound… See more