CDT, CCT, SFS And Plate Tectonic Theories Flashcards
CDT was proposed by ——
Alfred Wegener in 1912
Pangea broke up in ____ about _____ years ago
Broke in Laurasia and Gondawanaland separated by Tethys Sea around 225 Myr ago
What were the super continent and super ocean called in CDT?
Pangea and Panthalassa
Evidences of CDT
-Jig Saw Fit
-age and type of rocks across SA and Africa
-and Appalachian Mt (NA) and Caledonian Mt. (Europe)
-Similar tillite deposits (sedimetary rocks formed from glaciers) in India, Africa, Madagascar, Antarctica, Australia
-Rich placer deposits of gold found in Ghana, but souce (gold bearing veins) in Brazil
-Distribution of fossils across continents (mesosaurus)
Convection Current Theory was given by
Arthur Holmes in 1930s
What is the convection current theory
Convectional currents are present in the mantle due to radioactive elements
Radioactive elements give rise to difference in temperature— convection current —- drift of continents
Rising and sinking limbs of magma give rise to ______ and _____ of tectonic plates, respectively
Divergence and convergence
Evidences of Sea floor spreading
-Mid oceanic ridges
-rocks near MOR less dense — newer
-MOR composed of SIMA not SIAL
-Magnetic stripping / paleomagnetism — rocks near MOR younger
Destructive margin results from _____ plates
Converging
Constructive margin results from _____ plates
Diverging
Transform boundary is ____ marging
Conservative
Volcanoes are formed only when one plate is ___
Oceanic
Fold mountains are formed only when one plate is _____
Continental
Benioff zone
Region of active subduction
Oceanic plate subducts below continental
Block mountains and rift valleys result from
Divergence of plates
