Global Volcanism Program | Image GVP-07849
The 84,000-year-old Los Chocoyos Ash from Atitlán caldera is exposed in a quarry near San Juan Ostuncalco, west of Quetzaltenango. The white layer at the base is layer H, a rhyolite unit that is one of the largest known Plinian fall deposits in Central America. Despite its relative thinness, it is preserved over the entire Guatemalan highlands. The thicker overlying unit is the pyroclastic flow deposit, part of the Los Chocoyos ash. This massive unwelded pyroclastic flow deposit is up to 200 m thick.
Photo by Bill Rose, 1974 (Michigan Technological University).