BackgroundAn extensive Plio-Pleistocene volcanic field is located at the northern end of the Atenguillo graben in the Jalisco tectonic block of western México. Pleistocene volcanism has occurred at two locations at the southern and northern ends of the field. Potassium-Argon ages of 0.65 and 0.67 Ma (million years) were obtained from the Las Laja shield volcano at the southern end of the volcanic field. Initial phreatomagmatic eruptions at La Laja produced pyroclastic-surge and airfall deposits associated with formation of a tuff ring or tuff cone. Subsequently the extrusion of a thick sequence of lava flows formed the symmetrical shield volcano. The flows blocked the Río Atenguillo, forming an ephemeral 20-km-long lake, and the initial flows produced pillow lavas. El Rosario, the northernmost known Pleistocene vent of the Atenguillo graben, forms an alkali-basaltic lava plateau and has a Potassium-Argon age of 0.64 Ma.
Source: Smithsonian / GVP volcano information
See also: Sentinel hub | Landsat 8