Scientists use a COSPEC (Correlation Spectraphotometer) instrument to measure the sulfur dioxide (SO2) content of a volcanic plume from Fuego volcano in Guatemala. Measurements of the concentrations of SO2 and other gases in volcanic plumes are useful tools for eruption monitoring. This photo was taken from Finca Capetillo NE of Fuego during its October 1974 eruption.
Pyroclastic flows sweep down the east flank of Fuego volcano, Guatemala, in October 1974, during one of the largest historical eruptions of the volcano. Ash clouds rise off the base of the pyroclastic flows, which traveled up to 7 km from the summit at estimated average velocities of 60 km/hr. The travel direction of pyroclastic flows is influenced by topography. The denser basal portion of the pyroclastic flows follows topographic lows on the flanks of the volcano--note a smaller pyroclastic flow descending a gully at the right.
Fuego (left) and Acatenango are two of several paired volcanoes in Guatemala. Southward-younging volcanism constructed these two large stratovolcanoes and flank vents perpendicular to the trend of the Guatemalan volcanic front. The chemistry of lavas also varied progressively from dominantly andesitic at Acatenango to increasingly basaltic at Fuego. Activity from the Pleistocene-Holocene Acatenango has continued only sporadically into historical time, but Fuego is one of the most active volcanoes in Guatemala, with about 60 historical eruptions.
This roadcut provides an outstanding section through a debris-avalanche deposit from Fuego volcano in Guatemala. The pronounced color mottling is a common texture of debris-avalanche deposits. It distinguishes them from deposits produced by other volcanic processes such as mudflows or pyroclastic flows. This texture results from the transport of coherent segments of the volcano over long distances with only partial disaggregation. Note that individual lava flow segments and pyroclastic units can be traced across small offsetting faults.
The hummocky surface in the foreground in front of the twin volcanoes of Fuego and Acatenango in Guatemala is a massive debris-avalanche deposit produced by collapse of ancestral Fuego volcano during the early Holocene. The avalanche, the largest known in Guatemala, has an estimated volume of about 15 cu km and traveled 50 km from its source at Fuego. The avalanche traveled for its last 30 km over flat Pacific coastal plain slopes of less than 1 degree, illustrating the extremely high mobility of volcanic debris avalanches.