Notes on the 1902 eruption of Santa María volcano, Guatemala

Abstract

The first historic activity of Santa María volcano, Guatemala constituted one of the ten largest historic eruptions in the world, producing 5.5 km³ of debris. In hindsight, the six-month period before the October 1902 eruption was one of extremely abnormal seismicity in all of western Guatemala. The pyroclastis from the eruption were scattered widely over Western Guatemala and Southern Mexico and also caused world-wide atmospheric effects. The volcanics produced were of andesitic-dacitic composition, but there was wide variation from place to place in the sampled material — a fact apparently chiefly attributable to atmospheric-fractionation. There was apparently a change in chemistry of ash during the two-day eruption as well, the first, most voluminous ash was pumicious and white; later ash was finer, denser, darker, and slightly less silicious. The kinetic energy/thermal energy partition is determined to be similar to the value derived for Krakatoa,E _k/E _th ≅ 5.0 %. The thermal energy of the eruption was estimated at 4.2×10²⁵ ergs. The explosion crater left on Santa María’s southwest flank after the eruption had a volume equal to less than 0.5 km³, a small fraction of the volume of material erupted. The two-day 1902 blast has greatly overshadowed subsequent activity; extrusion of the Santiaguito dome, which has occurred since 1922 in the explosion crater, has produced about 0.7 km³ of dacite lava and 1.6×10²⁵ ergs of thermal energy in 48 years of activity.