Spatter cones form when blobs of molten magma that are ejected from a vent by mild explosions solidify around the vent and form a steep-sided cone. This small spatter cone formed in MacKenney crater of Pacaya volcano in Guatemala on February 10, 1985. This was part of an ongoing eruption of Pacaya that began in 1965. At the time of this photo, the spatter cone was 6-m high, ejected incandescent volcanic bombs from its vent, and issued lava from its eastern (left) side.
MacKenney cone, the historically active vent of Pacaya volcano in Guatemala, was constructed within a horseshoe-shaped caldera produced by collapse of the summit of an ancestral volcano about 1100 years ago. The SW caldera rim forms the steep-sided scarp at the right, and the small knob halfway down the left-hand skyline is a remnant of the partially buried opposite rim. The blocky hill in the foreground is a hummock from the debris avalanche produced by the collapse. The avalanche traveled 25 km down to the Pacific coastal plain.
Strombolian eruptions at Pacaya volcano in Guatemala produce a colorful nighttime display. This November 1988 time exposure traces the incandescent parabolic arcs of individual volcanic bombs explosively ejected from the vent. Larger bombs remain incandescent after they hit the surface of the cone and roll down its flank. The orange line at the lower right is a lava flow that issued from a fissure on the upper NW flank of MacKenney cone.