GEOG 001 Lecture Notes - Lecture 18: Convergent Boundary, Subduction, Garibaldi Provincial Park
19 Aug 2020
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Document Summary
Volcanic activity is directly related to plate tectonics and mot active volcanoes are located near plate boundaries. Mid-ocean ridges and subduction zones are sites where molten rock, or magma, reaches the surface and erupts as lava. 2/3 of all active volcanoes on land are located along the ring of fire which surrounds the pacific ocean lying above the subduction zones bordering the pacific, nazca, philippine, and juan de fuca plates. Composed of melted silicate minerals and dissolved gases. Main elements are oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, and potassium. O, and si are the must abundant minerals; magma contains small but significant amounts of dissolved gases. Silica-rich (made up of silicon and oxygen) magma, like molasses, does not flow easily and has a high viscosity. Magma with low silica content flows more easily, like warm honey and has a low viscosity. Eruption of volcanoes is like uncorking a bottle of champagne.
