Geophysical research: article

Аnnotation: Most of the present mountain ranges and high plateaus have been formed during the past few million years due to an abrupt acceleration of the crustal uplift. According to a very large volume of the formed relief, recent crustal uplift represents the most powerful phenomenon in continental lithosphere. Several mechanisms have been proposed as the explanations. The most popular one is shortening of the crust due to its lateral compression. However, this mechanism is not applicable to ancient cratons that cover 70 % of the total continental area since strong shortening of the crust terminated in them half a billion years ago or earlier. Other possible explanations, such as dynamic topography in the mantle, delamination of mantle lithosphere and magmatic underplating are also inconsistent with the available geological and geophysical data for the Precambrian cratons. It can be supposed that recent crustal uplift in such areas was the result of expansion of rocks in the crustal layer due to retrograde metamorphism under infiltration of mantle fluids. Penetration of fluids into large faults in the earth's crust reduced their strength. Together with lateral heterogeneity of recent crustal uplift this contributed to the occurrence of large earthquakes. The examples are the New Madrid earthquakes in 1811-1812 with the magnitudes M»8 in the South-East of the North American Platform, and the earthquakes with M=4.2 and 4.7 in the Vyatka Aulacogen on the East European Platform. Therefore, the Precambrian cratons are not so seismically “quiet”, as is often supposed.