Hence the Be prepared for earthquakes shirt, deformation or any kind of movements in the past 2 billion years or more. The geologists assign an area as hazardous or susceptible to earthquakes on the basis of the active fault lines in an area. Mainly the faulting is observed along the plate margins. But shield rocks are generally exposed on the flat plains in the central areas of plates. Shields are normally nucleus of continents surrounded by folded Precambrian rocks. Shields lack mountains because of non-involvement in the orogeny which involves faulting and uplifting. Hence the mountains formed during the last stages of tectonic activities at the shields are eroded away at the passage of time. The shield is not totally flat generally but shows a very gentle convex upward topography.
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Be prepared for earthquakes shirt. Platforms differ from the shield in such a way that platform is comprised of sediments which overlay the crystalline basement. Together the basement, platform, and shield which make the stable areas of a continent are known as craton. The margins of the shields are involved in tectonic movements and have indicated the complex orogeny in the past few hundred million years. For example, the Ural mountains, to the west of the Angaran shield are atop the mobile zone that separates the shield from the Baltic Shield. Similarly, the boundry of Angaran Shield and Indian shield is marked by the Himalayas. Shield margins have been subject to geotectonic forces that have both destroyed and rebuilt the margins and the cratons that they partially comprise.p.