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6 Cards in this Set
- Front
- Back
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Pele’s hair
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tiny strands and droplets of fountaining lava, also caught by the wind, that harden in the air. Glassy and pellet like strings.
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pillow structures
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when fluid lava erupts under water of flows from a tube that open in the ocean, pillow structures may form.
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Hawaii sits on top of a “hotspot”, or active mantle plume. Summarize this idea. Explain how Hawaiian volcanoes and the Hawaiian Islands chain support this theory.
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The most likely hypothesis suggests the existence of an immobile hot spot, a thermal high at depth, that melts rock material below the overriding Pacific plate. The magma accumulates in pockets that bulge up and eventually break through a stretched or weakened place in the crust. Hot lava rises and then fissures to the ocean floor. The release of great quantities of basaltic lava builds up shield volcanoes. As the Pacific plate drifts slowly northwestward, successive volcanoes from over the hot sport, are rafted away on the moving plate, and become dormant as they are cut off from the source of fresh magma. The hot spot theory thus explains the pattern of a volcanic chain with active volcanoes at the southest end and older volcanoes becoming inactive or extinct toward the northwest.
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In Hawaii Volcanoes National Park, pahoehoe and aa lava flows are common.
What are the characteristics of each type of lava flow? |
Pahoehoe is fluid, smooth, billowy or ropy lava. AA has a rough, jagged, or clinkery surface.
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Which type of lava can change into the other, if there is a loss of gas and a change in viscosity?
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Pahohoehoe can change into aa lava. The change involves the initial gas content of the lava and changes in lava viscosity.
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How do a) lava tubes and b) tree molds form as a result of pahoehoe flows?
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Lava tubes are tubes created when beneath the congealing surface of a pahoehoe flow, hot lava flows out to the moving front. Later, when the whole mass has cooled, the tubes remain.
Tree molds show where tree trunks stood before they were consumed by pahoehoe lava. |
