Santiaguito is the Guatemalan lava-dome complex that began erupting in 1922 on the flank of Santa María.
Santiaguito formed in the crater left by Santa María’s catastrophic 1902 eruption, one of the largest eruptions of the twentieth century. After about two decades of dormancy, new lava began extruding in 1922, building a complex of overlapping domes on the volcano’s southwestern flank.
The complex has four principal domes: El Caliente, La Mitad, El Monje, and El Brujo. El Caliente has generally been the active vent. Instead of producing a single, tidy cone, Santiaguito grows through cycles of lava extrusion, dome expansion, lava flows, rockfalls, ash explosions, and occasional pyroclastic flows.
Santiaguito is often confused with Santa María itself. Santa María is the larger parent stratovolcano, while Santiaguito is the younger dome complex created after the 1902 blast. The activity can look relatively gentle when viscous lava slowly piles up, but dome collapse can be deadly. In 1929, a major collapse generated pyroclastic flows that killed hundreds and possibly several thousand people.