i. Explain structural components of continents in detail and summarize it in pictorial form ii. Why the...

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Civil Engineering

i. Explain structural components of continents in detail
and summarize it in pictorial form
ii. Why the earth has oblate spheroid shape? Explain in
detail

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1First we will discuss about formation of continents and afterthat inner structure will be explained11 Structure of continentsThe surface of continents can be subdivided into several broadregions which were formed atdifferent times and by different tectonic processes These broadregions are referred to astectonic provincesShields lie at the heart of continents and are their oldestcomponents Shields are composed ofPrecambrian crystalline rocks metamorphic and igneous rocksThese rocks may have beendeformed during the Precambrian but remained undeformed during thePhanerozoic Examples ofshields are the Canadian Shield the African Shield and theAustralian ShieldPlatforms consist of sedimentary layers overlying the Precambrianbasement and displayingrelatively minor deformations eg North American PlatformSiberian Platform Shields andplatforms consist of the most stable parts of continents calledcratons Cratons have not beensignificantly affected by mountain building episodes orogeniesduring the Phanerozoic Howeverthey may have experienced slow vertical movements due to mantleconvection beneath thelithosphere or to the growth and retreat of ice sheets Largeareascan be uplifted due to heating by mantle upwelling beneath thelithosphere More locallymagmatic intrusions migrating upward can warp the overlying rocklayers Circular regions of thelithosphere which have been uplifted are called structural domeseg Cincinnati Arch USARichat Dome Mauritania Rock layers in a structural dome dip awayfrom its center On the otherhand regions of the lithosphere which cools and contracts areaffected by subsidence and arecalled thermal subsidence basinswhere abundant sediments can accumulate eg MichiganBasin USA Amadeus Basin Australia Unlike domes rock layers ina thermal subsidence basindip toward its center Intracratonic basins are economicallyimportant because they contain largereservoirs of coal oil and natural gasPhanerozoic orogens are mountain chains situated along the marginsof cratons and producedby continental collision or oceancontinent subduction TheAppalachian mountains eastern USAand the Ardennes central Europe are examples of past orogensrelated to mountain buildingepisodes that are no longer active On the other hand theAlpineHimalayan orogen and the Andesare examples of ongoing mountain building Regions of extended crust are regions where the last episode oftectonic deformation is anextension Passive margins are regions of extended crust becausethey are formed after rifting andthe subsequent opening of an ocean basin eg the passivecontinental margins bordering theAtlantic Ocean12Structure of earthStructure of EarthThe internal structure of Earth is layered inspherical shells an outer silicate See Answer

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