boundary layerThe layer of fluid adjacent to a physical boundary in which the fluid motion is significantly affected by the boundary and has a mean velocity less than the free stream value
ozone layerThe general stratum of the upper atmosphere in which there is an appreciable ozone concentration and in which ozone plays an important part in the radiative balance of the atmosphere
ozone layer depletion The fragile shield of ozone is been damaged by chemicals released on earth. The main chemicals that are depleting stratospheric ozone are chlorofluorocarbons which are used in refrigerators, aerosols, and as cleaners in many industries, and halons, which are used in fire extinguishers. The damage is caused when these chemicals release highly reactive forms of chlorine and bromine. Over the past 30 years ozone levels over parts of Antarctica have dropped by almost 40% during some months and a "hole" in ozone concentrations is clearly visible in satellite observations
soil layerDistinctive successive layers of soil produced by internal redistribution processes. Conventionally the layers have been divided into A, B and C horizons. The A horizon is the upper layer, containing humus and is leached and/or eluviated of many minerals. The B horizon forms a zone of deposition and is enriched with clay minerals and iron/aluminium oxides from the A layer. The C layer is the parent material for the present soil and may be partially weathered rock, transported glacial or alluvial material or an earlier soil
