The sharp spine is a collapse remnant of a lava flow extruded from the Caliente vent at the eastern side of Santiaguito lava dome between January 1972 and May 1973. A period of increased lava effusion between 1972 and 1975 was unusual in that major lava flows issued from vents at both ends of the lava-dome complex.

Photo by Bill Rose, 1978 (Michigan Technological University).

Santa María