Aeolian Processes 4
Past climate changes can be seen in many features that are found in the aeolian environments. These features in the arid areas that indicate wet conditions in the past such as the palaeo lakes and beaches. The example from Ejina Basin Inner Mongolia shows the palaeo lakes and beaches can vanish under the influence of climate change. These ancient features were formed during periods of wetter climates, and now have completely dried up. Sometimes, you can not find any trace of water in that area. By studying the evidences in those areas, we can reconstruct the palaeo environment and predict the changes in the future. Scientists can now collect samples using cores from the bottom of the palaeo lakes in order to analyse the past climatic conditions in these areas.
When there in increased runoff, it becomes concentrated into deep steep-sided ravines known as wadis. Normally dry wadis or arroyos may be subjected to irregular flash floods. The average occurrence of these floods is once a year in the semi-arid margins of the Sahara and once a decade in the extremely arid interior. This infrequency of floods compared to the great number and size of wadis, suggests that they are a relict feature created by processes no longer taking place.The increasing aridity due to changing climate has been discussed in further detail by the desertification site.
In the past the lake attracted a large population and formed a large city. The example of the ruined civilization in desert area in the Heicheng (Black City) in Ejina Basin Inner Mongolia, China was ruined by the army in Ming Dynasty in the 1372. The scope of ruined city construction and the dead forest and the lacustrine deposits in the area indicate that even the environment in the area was not good but was suitable for living and could support hundreds of people, plants and livestock in the area. It shows that as soon as the ecosystem collapse it is difficult even impossible to rescue. More information on the hidden black city can be found here.
Palaeo beaches at the edge of Badaim Jaran desert, Ejina Basin, Inner Mongolia, China, Photos by M. Jin, 2005.