EARTHSC 2GG3 Lecture 4: Lecture 4- Volcanoes
24 Dec 2016
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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 a(cid:396)e fou(cid:374)d o(cid:374) the (cid:858) i(cid:374)g of fi(cid:396)e(cid:859) su(cid:396)(cid:396)ou(cid:374)di(cid:374)g the pa(cid:272)ifi(cid:272) o(cid:272)ea(cid:374). Subduction zones and mid-ocean ridges allow molten rock to reach the surface. It is found deep within the crust and upper mantle. 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 ea(cid:396)th(cid:859)s su(cid:396)fa(cid:272)e. 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 in the rocks. Types of volcanic rocks: basalt(most common), 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(the resistance to flow) of their magma. Magma viscosity is determined by silica content and temperature. Cooler, more viscous, more gases-big explosions, big ash cloud.
