Comondu-La Purisima volcanComondú-La Purísima volcano is a volcanic field of about 9000 sq km in southern Baja California, west of the Sierra de la Giganta.
Volcanic activity of La Purısima dates back about 10 million years ago, but might have continued into the Holocene (i.e. less than 10,000 years ago), as some of the cinder cones and blocky lava flows, in the area between Comondú and the La Purísima river, have preserved a very fresh morphology.
Introduction:The field was formed about 10 million years ago as a consequence of subduction of the Farallon and Guadalupe plates below Baja California. Vents in the Comondú-La Purísima volcanic fields usually occur along NNW-trending faults, and many lava flows are offset, sometimes repeatedly, along grabens. There are both basaltic and andesitic lava flows. The basaltic flows are typically 5-10 m thin while andesitic flows, due to their greater viscosity are up to 60-80 m thick and form dense, glassy flows with subhorizontal fractures.
Cliquez ici pour recommander cette page à un ami