Definition characters description and diffusion
The first synthesis of complexity is the oasis intended as an artifical accomplishment deriving from a perfect knowledge of the environment. A slight depression collects humidity, a stone provides shade and a seed flourishes. Thus, favorable dynamics develop: the plant generates its protection from the sun's rays, concentrates water vapour, attracts insects, produces biological material an the soil from which it subsequently draws its nourishment.
General characters description and diffusion
By using these processes people from the Sahara create erg oases. Erg oases follow the laws regulating the formation of the great ocean of sand and use those laws to set up protective dune barriers. They are not based on a geomorphologic structure or on a well-defined hydrographical system becuase the ridge is covered with sands. In some cases, erg oases depend on shallow underground water that the roots of the palm trees can directly reach in the subsoil. Therefore, these palms groves do not need to be irrigated and, in fact, they are called bur, which means not irrigated. The farmer has the harder task of sweeping the sands from the isles of palm groves. The farmer starts to dig out a ditch enabling the palm trees to reach the humid area of the soil. Dried palm leaves are arranged around the circular cavity becuase they slow down the power of the wind and cause the sand to be released.
Advantages and sustainability
Erg oases use natural process to create shading from the sun, absorption of humidity, concentration of water vapor, and attraction of insects, which ultimately lead to biological matter in the soil from which it takes nourishment. In erg oases, palm trees do not need to be irrigated.