EARTHSC 2GG3 Lecture Notes - Lecture 4: Pyroclastic Rock, Volcanic Crater, Magma Chamber
12 Jan 2017
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Most volcanoes are located near plate boundaries. (cid:1006)/(cid:1007) of all (cid:448)ol(cid:272)a(cid:374)oes are fou(cid:374)d o(cid:374) the (cid:858) i(cid:374)g of fire(cid:859) surrou(cid:374)di(cid:374)g the. Subduction zones and mid-ocean ridges allow molten rock to reach the surface. Magma: it is found deep within the crust and upper mantle. Lava: it is found flowing from an erupting volcano. Esse(cid:374)tially, la(cid:448)a is (cid:373)ag(cid:373)a o(cid:374) the earth(cid:859)s surface. The most abundant elements in magma are silicon and oxygen; when combined they are referred to as silica. Volcanic rocks are named based on the amount of silica present. Types of volcanic rocks: basalt, andesite, dacite, rhyolite, low silica high silica. Magma also contains small amounts of gases (water vapour and carbon dioxide). Volcanoes have different shapes based on the chemistry and viscosity of their magma. Magma viscosity is determined by silica content and temperature. Magma with high silica content: cooler, more viscous, more gases. Magma with low silica content: hotter, less viscous, fewer gases.
