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Because dacite is the main type of lava erupted from Mount Garibaldi, lava flows are a low to moderate hazard. [3] Dacite is felsic [ d ] in composition, containing 62–69% silica content. [ 71 ] [ 72 ] This high percentage in silica content increases the viscosity of dacitic melts relative to that of andesite or basalt , generally resulting ...
Northwest of the summit, a dacitic lava dome is the source of a 500-metre-high (1,600 ft) talus slope. [31] The summit area is surrounded by an inwards-dropping scarp that opens to the northwest and whose southern margin is buried by lava flows. Pyroclastic flows crop out beneath lava flows in the northwestern segment of the volcano, within the ...
The Loop was born in political scandal: upon completion, all the rail lines running downtown had to pay Yerkes's operation a fee, which raised fares for commuters; when Yerkes, after bribery of the state legislature, secured legislation by which he claimed a fifty-year franchise, the resulting furor drove him out of town and ushered in a short ...
Low viscosity lava can generate massive lava fountains, while lava of thicker viscosity can solidify within the vent, creating a volcanic plug. Volcanic plugs can trap volcanic gas and create pressure in the magma chamber, resulting in violent eruptions. [36] Lava is typically between 700 and 1,200 °C (1,300–2,200 °F). [37]
Dacite and rhyolite lavas are normally too viscous to flow away from a volcanic vent, resulting in the formation of lava domes. [25] An exception is the 15-kilometre-long (9.3-mile) Ring Creek dacite lava flow from Opal Cone on the southeastern flank of Mount Garibaldi, a length that is normally attained by basaltic lava flows. [19]
The Greenstone Flow is one of the world's largest known lava flows, estimated at a volume ~1650 to ~6000 cubic kilometers of mafic lava. [2] [3] In places, the lava pooled to depth of 487 meters. [4] The flow was generated by a flood basalt eruption during the Midcontinental Rift, which occurred 1.1 billion years ago. [5]
The word lava comes from Italian and is probably derived from the Latin word labes, which means a fall or slide. [2] [3] An early use of the word in connection with extrusion of magma from below the surface is found in a short account of the 1737 eruption of Vesuvius, written by Francesco Serao, who described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of ...
Rootless cones are formed by steam explosions as flowing hot lava crosses over a wet surface, such as a swamp, a lake, or a pond. The explosive gases break through the lava surface in a manner similar to a phreatic eruption , and the tephra builds up crater-like forms which can appear very similar to real volcanic craters.