The most recent eruption was about 2,200 years ago and covered the eastern half of the park with up to one foot of lapilli, blocks, and bombs. USGS photograph, D.R. Crandell. Volcanism continued after the caldera formed. Within a few hundred years cones had formed inside the caldera. Eventually, the crater filled with water.
Wizard Island is the top of one of the cones.
Llao Rock forms the step cliff along the caldera wall in the top left of the photo. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. This image was produced at the JPL Multimission Image Processing Laboratory.