Volcanic Environments

Learning goal To understand the natural processes affecting the distribution of volcanic environments

Continental crust Plates consist of either continental crust or oceanic crust The continental crust is older, thicker (35 to 75 kilometres), lighter (mainly granite) and cannot sink Continental crust extends beyond the present coastline to the edge of the continental shelf of each continental mass

Oceanic crust The oceanic crust is younger, thinner (less than 10km) heavier (mainly basalt), can sink (be subducted) into the mantle and is constantly being destroyed and replaced. These differences account for the variations in the level of both volcanic and earthquake activity at plate boundaries, and the variations in landforms

Cheesy Rap http://www.youtube.com/watch?v=dkELENdZukI

Type of volcanic activity The level and type of volcanic activity are determined by the direction of the plate movement and whether the plates are oceanic or continental The oceanic plates consist mainly of basalt, which originates from the rising magma in the upper part of the mantle, beneath the ocean ridges as the plates pull apart Where the oceanic plate is subducted under the continental plate, the molten material, magma, consists of 3 different materials: some from the upper mantle directly above the descending oceanic plate, some from the partial melting of the oceanic plate itself and some from the lower part of the continental shelf This results in the volcanic rocks formed under continental plates being far more complex than the volcanic rocks formed under oceanic plates.