Geographical factors of the abundance of flora in Russian cities

Doklady Earth Sciences - An analysis of data on the species abundance of flora in 89 cities (urban flora) of the Russian Federation facilitated determination of its main factors. It has been...     

Separation of volatile components from rocks under mechanical loading as the source of hydrogeochemical anomalies preceding earthquakes

One of the most important problems for the theory and practice of earthquake prediction is that of the source of substances in the formation of precursory hydrogeochemical anomalies. Volatile components that are separated from rocks at mechanical loading present one of the sources. A large-scale model experiment is conducte with a 50 000-ton press; the results reveal the regularities of water, radon, mercury, and helium separation from large basalt and granite samples that are subjected to a cyclically increasing, uniaxial pressure to fracture (at 75 and 180 MPa for basalt and granite, respectively). Premonitory rock fracture is found to be accompanied by the separation of volatile components from rocks. Predictive properties of the components are associated with their chemical nature and the forms in which they exist in rocks. Water release during mechanical loading increases gradually with the increase in loading. Helium separation begins at the early stages of the cracking process. Comparison of the data on degassing with data on bulk strain and acoustic emission shows that the major part of radon is released at the stage of avalanche-type crack interaction and at the dynamic stage of the formation of an earthquake source, whereas mercury degasses mainly at the dynamic stage immediately before fracture of the sample.