Global Volcanism Program | Image GVP-07570
The low-angle La Laja shield volcano lies at the southern end of the Plio-Pleistocene Northern Atenguillo volcanic field in the Jalisco tectonic block of western México. La Laja was dated at about 660,000 years. Initial phreatomagmatic eruptions at La Laja produced pyroclastic-surge and airfall deposits. These were followed by the extrusion of a thick sequence of lava flows that built the symmetrical shield volcano. The flows blocked the Río Atenguillo, forming an ephemeral 20-km-long lake.
Photo by Paul Wallace, 1998 (University of California Berkeley).