What is a lava dome and how is it formed?
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wickedwillie
ANSWERS: 2
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A lava dome is a mound of cooled or cooling lava that forms in a volcano's vent. These are made of viscous lavas with compositions that range from andesite to rhyolite (the kind that comes out of Mt. St. Helens). The closer the composition is the rhyolite end, the more viscus the lava, and, therefore, the more likely the lava is to form a dome rather than a flow. Lava domes form because the lava is too viscous to flow readily. Therefore, it does not get very far before it cools and solidifies. So, as more lava oozes out, it just creates a heap around the vent. This is as opposed to what happens with a very fluid like basalt (the kind that comes out of the Hawaiian volcanoes). This type of lava can flow for tens of miles from the vent before it cools and solidifies.
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