Pene-contemporaneous tectonics along tlle mexican paciflc ocean coast

Abstract

Toward the middle of the last century, Alexander von Humboldt (1867) expressed the idea that the great concentration of volcanocs ou parallel 19° across Mexico was due to a major fracture in the earth's crust. A hundred years later investigation made in the Pacific Ocean by geologists of the Scripps Institution of Oceanography proved conclusively the existence of such a fracture, which continues far out into the Pacific Ocean in the Clarion Fracture Zone. In the light of these results, the Revillagigedo Islands represent the jutting peaks of enormous volcanic complcxes which rise abruptly from depths of 4,000 meters over the mentioncd zone, and are comparable to the volcanic giants Popocatepetl and Iztaccihuatl on the Mexican land-mass.