Los Humeros

Los Humeros is the easternmost of a series of silicic volcanic centers with active geothermal systems located north of the axis of the Mexican Volcanic Belt. The first major silicic eruption produced the 230 km3 Xáltipan Ignimbrite about 460,000 years before present (BP), which covered about 3,500 km2 and resulted in formation of the 15 x 21 km Los Humeros caldera. The emplacement of post-caldera lava domes and eruption of the 40 km3 Faby Tuff about 240,000 years BP was followed by eruption of the Zaragoza Tuff about 100,000 years BP and formation of the nested 10-km-wide Los Potreros caldera. A third and much smaller caldera (El Xalapazco) was formed about 40,000-20,000 years BP. The most recent eruptions include the production of extensive morphologically youthful basaltic lava flows that are undated, but are younger than a 20,000 BP rhyolitic lava flow and could be in part of early Holocene age. A major explosive eruption about 6,400 years ago produced the bimodal Plinian Cuilcuiltic Member tephra.