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Tortuga, Isla
"A youthful shield volcano forms Isla Tortuga, which lies in the Gulf of California 40 km off the Baja coast. A circular, 1-km-wide caldera, west of the center of the oval, 4-km-long island, truncates the small shield volcano, which reaches only about 210 m above sea level. Circumferential faults cut the rim of the >100-m-deep caldera, which is floored by a solidified lava lake and contains youthful-looking spatter cones. The shield volcano was constructed during two north-migrating periods of activity that began with submarine eruptions and included formation of a circular tuff-ring complex enclosing the caldera. The sides of a small volcanic horst in the center of the caldera display lava flows overlying a 2-m-thick halite bed, formed when sea water filled the caldera, creating an evaporite basin. Recent lava flows cover most of the flanks of the volcano, and fumarolic activity has continued into historical time."  -Smithsonian Volcano Archive
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