Geology Summary on Lava Deltas

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Lava deltas are created when pahoehoe goes into the ocean and stays there for a long time. Lava deltas are fan shaped pieces of land that form in the ocean. When the lava flows into the ocean, it cools really quickly and breaks into pieces, which can be sand sized or block sized. The different pieces collect on a slope underwater and build the base of a structure that in time can hold up the lava flows that form the delta above the water. When the pieces of lava collect on a steep slope, then the side of the delta crumbles often and creates a bunch of submarine landslides. Collapses like this can catch unsuspecting people and push them into the ocean and sometimes also cause big explosions. Lava deltas get wider to the sides as well as longer out into the water until a landslide happens or until the lava flow to the water is stopped. First, the pahoehoe lava is thick and slowly moves across the beach or drops over a small cliff. Waves from the ocean slosh onto the lava, causing the lava to cool at a rapid pace and break into tiny glass pieces. Explosions are rare since the ocean water doesn’t get caught inside the lava. Because of the infrequency of explosions, the safest time to get near the lava going into the ocean is within the first couple hours of it going into the water. “When Lava Enters the Sea: Growth & Collapse of Lava Deltas." usgs.gov. US Geological Survey, 2004. Web. 2 April 2014. http://hvo.wr.usgs.gov/hazards/oceanentry/deltacollapse/
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