The word lithosphere has two major meanings in the scientific community, a specific one and a more general one. The specific meaning is more common in geology, as it is essential to the theory of plate tectonics.
Significance
The word lithosphere usually refers to the crust and outer mantle of the Earth's surface. It may also refer to the outer shell of any rocky planet. This noun is used in geology and earth science to distinguish the hard part of the Earth's surface from other layers, such as the asthenosphere, or molten layer of the mantle. In some cases, the word lithosphere can also mean the entire solid part of the earth, as distinguished from the hydrosphere, or oceans, and the atmosphere, or air surrounding the planet.
History
The word lithosphere comes from the Greek "litho," meaning stone, and "sphere" from the Greek "sphaira," meaning a globe or ball. Joseph Barrell introduced the scientific community to the word lithosphere in 1914, when his writings posited the idea of a hard upper layer on the Earth's crust called the lithosphere and a softer layer underneath called the asthenosphere. The word lithosphere continued to gain importance in geology throughout the 1940s, and the concept became essential to plate tectonic theory in the 1960s. For this reason, tectonic plates may also be called lithospheric plates.
Types
The Earth has two types of lithosphere. The oceanic lithosphere, or part beneath the oceans, is about 55 kilometers (34 miles) thick. The continental lithosphere is typically thicker and older, and may be up to 200 kilometers (124 miles) deep. Both types are part of the Earth's lithosphere, and they each provide unique opportunities for scientific studies.
Identification
All of the Earth's crust, or rocky outer layer, is part of the lithosphere. Some of the Earth's upper mantle is also in the lithosphere. The distinction between the crust and mantle is based on the chemical properties of the layers. In contrast, the distinction between the lithosphere and asthenosphere is based on its behavior. While the asthenosphere remains flexible during the plate tectonics process, the lithosphere, or rocky surface, remains rigid and breaks or deforms.
Geography
The lithosphere is made up of tectonic, or lithospheric, plates. These plates include both continents and oceans. Geologists currently recognize seven major plates, as well as many minor ones. The major continental plates include including the African, Antarctic, Australian, Eurasian, North American and South American plates. The Indian continental plate includes the land of India, as well as parts of the Indian Ocean. The Pacific plate is a major oceanic plate. All of these plates are part of the lithosphere.
Tags: word lithosphere, distinction between, Earth crust, Earth surface, from Greek, kilometers miles
