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What are the characteristics of plate boundaries?


Following is a brief summary (in outline form)


Divergent Plate Boundaries

Igneous environment:

Extrusive: Mafic volcanics - very hot and fluid

Basalt flows, pillows, and breccias

Low in gas and water - relatively quiet and non-explosive

Intrusive: Mafic plutons and sheeted dike complexes

Tectonics: Extensional environment

Very thin crust with a high heat flow

Normal faults

Generally shallow focus earthquakes

Relatively low Richter magnitudes


Convergent Plate Boundaries

Igneous environment:

Extrusive: Intermediate volcanics

Andesite breccias, pyroclastics, and flows

High in gas and water - very explosive volcanoes

Intrusive: Felsic to intermediate plutons

Commonly the location of large granitic plutons

Tectonics: Compressional environment

Transitional crust relative to thickness

Reverse faults

Shallow to deep focus earthquakes

Low to very high Richter magnitudes (hang on tight)


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