A sedimentary and architectural unit defined by a combination of lithological, pedological, and material cultural criteria: Archaeological layers are created over time as people develop new towns and cities, and then rebuilt them at the same place, as it is the case in Istanbul.

The thin layer of air adjacent to the Earth's surface; surface layer: The atmospheric boundary layer is usually considered to be less than 300 feet (91 meters) high.

In the Earth's atmosphere, the planetary boundary layer is the air layer near the ground affected by diurnal heat, moisture, or momentum transfer to or from the surface.

The thin layer of air adjacent to the Earth's surface; ground layer: The atmospheric boundary layer extends up to the so-called anemometer level (the base of the Ekman layer [thin top layer of the sea]). Within this layer the wind distribution is determined largely by the vertical temperature gradient and the nature and contours of the underlying surface, and shearing stresses are approximately constant.

Any one of a number of layers of the atmosphere, most commonly distinguished by temperature distribution: The atmospheric layer is also known as the "atmospheric shell" or "atmospheric region".

The atmospheric layer is one of several strata or layers of the Earth's atmosphere.

Temperature distribution is the most common criterion used for denoting the various shells.

1. A process that takes place at a solid-liquid interface.

It is made up of ions of one charge type which are fixed to the surface of the solid and an equal number of mobile ions of the opposite charge which are distributed through the neighboring region of the liquid.

2. The area of a charge separation formed when an electrode meets an ionic conductor.

A metal electrode in a water solution forms a specific structure consisting of the metal surface itself, an adjoining layer of adsorbed (adhesion to the surfaces of solids) water molecules and ions, and an outer region of oppositely charged ions diffused in the liquid.

This causes an electric field of considerable intensity.

3. An interfacial region, near the boundary between two different phases of a substance, in which physical properties change significantly.
4. A structure that appears on the surface of a charged object when it is placed into a liquid.

This object might be a solid particle, a gas bubble, a liquid droplet, or a porous body.

The leached (emptied or drained) upper part of a soil profile: The eluvial layer that lost the essential soil minerals from its light sandy soils was caused by a year of excessive rain.

The thin layer of the atmosphere adjacent to the earth's surface.

1. The part of the interior of the earth, or another planet, located below the crust and above the core, extending to a depth of about 3,500 kilometers below the surface.

The hot plastic asthenosphere, part upper mantle and lower crust about 186 miles (300 kilometers) thick, separates the more brittle crust-mantle lithosphere above from the mesosphere below.

This is thought to be responsible for the movement of the lithospheric plates (crustal plates) which slowly "carry" the continents around the planet.

The more solid mesosphere, which is located below he asthenosphere, includes part of the upper and all of the lower mantle.

2. The nuclear zone of the developing neural tube between the marginal layer and the ependymal layer (covering of internal and external surfaces of the body, including the lining of vessels and other small cavities); which forms the gray matter of the central nervous system.

1. A region in the upper atmosphere, about 6–30 miles (10–50 kilometers) high, with significant concentrations of ozone, formed by the effect of solar ultraviolet (UV) radiation on oxygen and also present in trace quantities elsewhere in earth's atmosphere.
2. The layer of the upper atmosphere, from 15 to 50 kilometers (10 to 30 miles) above the earth's surface, where most atmospheric ozone collects, absorbing harmful ultraviolet radiation from the sun.

In the 1980's it was realized that industrial pollutants such as CFC's were damaging the ozone layer and that holes had appeared in it, especially over the Antarctic.

CFC refers to a gas containing carbon, hydrogen, chlorine, and fluorine; some forms of which are said to damage the ozone layer in the earth's atmosphere.

Zone electrophoresis in which the supporting medium is applied in a thin layer to a glass or plastic strip.