EARTH121 Lecture Notes - Lecture 4: Basalt, Deccan Traps, Plate Tectonics
21 Dec 2017
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Chapter 4: volcanoes and volcanic processes: deadliest eruptions recorded in history from mount tambora & mt. Krakatoa; in indonesia factors deciding nature of volcanic eruptions: composition, temperature & amount of dissolved gases; affect viscosity. Mafic: very fluid; low silica, pahoehoe flows: congeal smooth with wrinkles forming above due to moving lava; braided, aa flow: surface of rough, jagged blocks with dangerously sharp edges and spiny projections; cool and thick. Pillow lavas: lava breaking through hardened lava over and over again. La(cid:448)a tu(cid:271)es: (cid:272)a(cid:448)elike tu(cid:374)(cid:374)els (cid:449)here la(cid:448)a (cid:449)as (cid:373)ost likely (cid:272)arried fro(cid:373) (cid:448)ol(cid:272)a(cid:374)i(cid:272) (cid:448)e(cid:374)t to flo(cid:449)"s leading edge. Pyroclastic materials: mafic lava being extruded to great heights w/ dissolved gases; some material near vent and some carried by wind. Bombs: made from hardened lava and ejected as incandescent lava; semi-molten. Pumice: intermediate or silica-rich composition generates vesicular ejecta. Pyroclastic flows: hot gases infused with incandescent ash and larger rock fragments. Nu es ardentes: glowing avalanches; fiery flows and very speedy.
