ESS 101 Lecture Notes - Lecture 9: Dacite, Tephra, Lava Dome
27 Feb 2017
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Document Summary
Large batholiths can form along collisional and convergent tectonic boundaries: large batholiths underlie or are exposed within the cascades, sierra nevada, Roof pendant (dark metamorphosed sedimentary rock) comprised of re(cid:373)(cid:374)a(cid:374)t (cid:862)(cid:272)ou(cid:374)try ro(cid:272)k(cid:863) is draped o(cid:448)er the you(cid:374)ger i(cid:374)truded ierra ne(cid:448)ada (cid:271)atholith (cid:894)light (cid:272)olored granodiorite) Stocks are irregular-shaped plutons that have a surface area of <100km2. Dikes are tabular intrusive bodies that are oriented perpendicular or oblique to layered country rock. Sills are tabular plutonic bodies that are oriented parallel to pre-existing sedimentary layers. Volcanic necks form when resistant magma is intruded into the vent and radial fractures of a volcano. Over time, the less resistant rock comprising the flank of the volcano is eroded away leaving the resistant rock exposed in relief. The nature of volcanic hazards is strongly tied to the viscosity and gas content of the magma; basaltic composition eruptions tend to be non-explosive (effusive)
