NASA / JPL / UA / composite and caption by Jason Perry
Zamama, a volcano on Io
Two low-sun images of Zamama from Galileo's I32 orbit (October 2001, left) and I24 (October 1999, right). Zamama consists of a 140-kilometer-long lava flow field that formed between 1979 and 1996 and was still active as of 2007. The scrambled raw data for the I24 image was unscrambled by a program developed at JPL using the LabVIEW software from National Instruments of Austin, TX.
The lava for this flow field erupts from a small shield volcano 40 kilometers wide and 1.5 kilometers tall. The peak of this volcano is surrounded (as you can see in the image on the right) by radiating lava flows. Flows to the south of the Zamama volcano are incised into the plains as well as the flanks of a shield volcano southeast of Zamama. A volcanic plume has been observed erupting from the center of the Zamama flow field, caused by the heating of sulfur dioxide surface frost by flowing silicate lava.