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what did wegner do
showed africa and s. america were joined, continetal drift, origin of continets and oceans
what are the characteristics of a divergent plate
sea floor spreading, new rock created, basaltic volcanism, techtonic stress, mid-ocean ridge
what are the characteristics of a convergent plate
subduction, rock destroyed, andositic volcanism, compression, ocean to continent
what did Arthur Holmes do
sonar data, mid-ocean ridge volcanic, convection in mantle due to changes in its density
what are the different phases of Alpine Glaciers
cirque- beginning, valley- growing, piedmont- outside of valley
how do extrusive igneous rocks form
from the cooling of lava or the bonding of pyroclastic materials on the aurface
what is a terrane
is a small-to-medium mass of lithosphere bounded on all sides by faults that may have been carried a long distance by a drifting plate, eventually to converge with the edge of another plate
have masses of very viscous lava such as high-silica rhyolite that are too thick and pasty to flow very far
what is caldera
large, steepsided, roughly circular depression resulting from the explosion and or collapse of a large volcano
what is volcanic mudflow
a loose mantle of ash and pyroclastic flow deposits on the slopes of a volcano can be mobilized easily by heavy rain or by the melting of snow and glaciers during an eruption
what is kettles
can form when large blocks of ice left by a retreating glacier become surrounded or even covered by glacial grift, after the ice melts the morainal surface collapses, leaving an irregular depression
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