GEO 1301 Study Guide - Midterm Guide: Kīlauea Iki, Stratovolcano, Vulcanian Eruption

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17 Apr 2015
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Explain the magma fragmentation process occurring during an explosive eruption. Why do rhyolitic lavas often form domes? he lavas that most frequently form domes are generally lavas that are higher in silica (sio2) and are thus generally more viscous. With increasing silica (sio2) content and polymerization, the viscosities of these felsic lavas will increase accordingly. Although dacitic-to-rhyolitic lavas typically erupt from stratovolcanoes, they are not as abundant as andesite lava. Instead, felsic eruptions from stratovolcanoes are more commonly explosive and associated with the generation of tephra and pyroclastic flows. These explosive eruptions are a function of the high viscosities and high gas contents of dacitic and rhyolitic magmas. Such eruptions, however, will often deplete the magma source in dissolved gases. De-gassed magma can then rise to the surface and extrude in a less violent fashion, as dacite to rhyolite lava. These lavas are volumetrically smaller than their pyroclastic counterparts, and typically form after major eruptive events.

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