GEOG 1350 Chapter Notes - Chapter 5: Igneous Rock, Pyroclastic Rock, Silicate Minerals
16 Aug 2016
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Document Summary
Volcanic activity is directly related to plate tectonics and most 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 are located in the pacific ring which surrounds the pacific ocean. How magma forms: the planet is composed of solid rock, most magmas come from the asthenosphere where rock is close to its melting temperature. Magma properties: (a) composition: composed of melted silicate minerals and dissolved gases, main elements are oxygen, silicon, aluminum, iron, magnesium, potassium, sodium, calcium. When silicon and oxygen (s and o) combine, they are called silica. Magma contains small but significant amounts of dissolved gases mostly water vapour and. Co2. (b) viscosity: a fluid"s resistance to flow, silica-rich magma does not flow easy and has a high viscosity, however regular magma flows easily with low viscosity.
