You are watching: Viscosity of a magma is controlled by
Resistance come flow-Viscosity depends upon temperature & magma composition (most important).-Magma ingredient varies through plate tectonic setting.-Pressure ~ above magma decreases as magma rises toward surface.-Gases room released as pressure decreases--(Carbonated drink analogy)
Oxygen and silicon that combines through other aspects (e.g., sodium, potassium) to form minerals.-Elements combine to kind simple frameworks in mineral with less SILICA = "low viscosity"-Elements combine to kind more complex structures in mineral with an ext SIILICA = HIGH viscosity
More violent eruptions-Gases to escape easily during mild eruptions v low viscosity magma, e.g., Hawaii-Gases to escape explosively indigenous high viscosity magma, e.g., Mt. St. Helens, Philippines
-Most active volcanoes uncovered near convergent bowl boundaries.--Others connected with divergent borders (Iceland, eastern Africa) or type above hot spots (Hawaii)-Cascade Mountains:--Volcanic arc in pacific Northwest---Mount St. Helens eruptions of might 18, 1980.
Volcanic Explosivity table of contents (VEI) procedures volume of erupted material-8 divisions on log range (x10 increases between divisions)
Airborne Eruption products:-Tephra-Lava Bombs-AshVolcanic gasesEruption commodities on Land:-Basalt-Lava-Lava Dome-Pyroclastic Flow-Lahars
represents particles blasted into air through eruption.-Volcanic bombs & ash are discovered near & far from eruption source, respectively.
(water vapor, sulfur dioxide, carbon dioxide) may impact climate patterns.-Sulfur dioxide may block solar radiation, temporarily reducing an international temperatures.
Dense cloud developed from combinations of tephra & volcanic gases.-Fast moving, temp up to 700 levels Celsius
Mudflows formed when volcanic debris mixes through streams or melting ice.-Often confined come stream channels.
1.) Shield2.) Stratovolcanoes3.) Cinder Cone-Composed of various materials-Volcano form & eruption style varies with plate setting-Different size (note: dimension of trees on volcano slopes).
-Broad, gentle slopes-Built from numerous low viscosity lava operation (basalt)-Relatively mild eruptions associated with warm spots, divergent key boundaries.
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-Most common volcano kind - likewise called COMPOSITE VOLCANOES.-Steeper slopes built from alternate layers the pyroclastic debris & viscous lava.-Form follow me subduction zones (convergent boundary).
-Smallest volcanoes, up to 400 meter in elevation-Built from an ext viscous magma commodities (course tephra)-May form on slopes the shield or stratovolcanoes
Giant crater formed from please of volcano right into underlying magma chamber.-e.g., Yellowstone, Wyoming & Crater Lake, Oregon