Geologists visited the summit 16, 17, and 18 February. There was no visible fumarolic activity around the summit, or in the explosion craters from the volcano's last eruption in 1972. The geologists smelled a strong sulfur odor in the immediate vicinity of the summit craters.

Geological Summary. Acatenango overlooks the city of Antigua, Guatemala, about 15 km NE of the summit, and the active Fuego volcano 3 km S. The two principal summits were constructed during three eruptive periods post-dating the roughly 85,000-year-old Los Chocoyos tephra from Atitlán caldera. An older Acatenango edifice collapsed to the south sometime prior to 43,000 years ago, forming La Democracia debris-avalanche deposit, which covers a wide area of the Pacific coastal plain. Construction of Yepocapa, the northern summit of Acatenango, was completed about 20,000 years ago, after which growth of the southern and highest cone, Pico Central (also known as Pico Mayor), began. The first well-documented eruptions took place from 1924 to 1927. Francisco Vasquez, writing in 1690, noted that in 1661 a volcano that lay aside of Fuego "opened a smoking mouth and still gives off smoke from another three, but without noise."

Information Contacts: T. Bornhorst and C. Chesner, Michigan Tech. Univ.