Geology of the islas revillagigedo,mexico |
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| Authors: | Adrian F Richards |
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| Institution: | 1. U. S. Navy Hydrographic Office, Washington, D. C.
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| Abstract: | On August 1, 1952, a new volcano named Bárcena was born on Isla San Benedicto, which is located about 300 nautical miles off the west coast of Mexico. A pyroclastic cone nearly 1100 feet above sea level was formed by August 2. By mid-September cone formation had ceased and a small lava plug capped the magma conduit in the crater. After a period of quiescence from mid-September until early November activity resumed and blocky, soda trachyte lava formed two domes in Bárcena crater during November and early December. On December 8 lava flowed through the base of the volcano and formed a delta nearly one-half mile out to sea by the end of February, 1953. All activity, except solfataric steaming, stopped by this date. Volcanic density flows («nuées ardentes ») descended the cone during the period of cone formation. As the expulsion of ash and steam decreased in early September, 1952, the exterior of the cone is believed to have been furrowed by these avalanches. Volcán Bárcena has an index of explosiveness of about 90 per cent, the highest of any known oceanic volcano in the eastern Pacific Ocean. Calculations indicate that about 10,500 million cubic feet (300 million cubic meters) of tephra and lava were erupted during the life of Bárcena. |
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