The images used to make this mosaic have been computer processed to emphasize surface relief and reduce the variations in surface reflectance (albedo). The complex caldera is composed of several discrete centers of collapse where the older collapse features are cross-cut by more recent collapse events. The lowermost circular floor preserves the last lava flooding event that followed the last major collapse. The southern wall of the caldera has at least 3 km (2 mi) of vertical relief with an average slope of at least 26º (from horizontal). The caldera complex truncates several lava flows, indicating that the flows predate the collapse event and that their source areas have been destroyed by the caldera formation. The arrow indicates the lava flow shown in slide #6.
11 N, 104 W; digital mosaic of Viking Orbiter frames 401B16 to 24, high-pass spatially filtered version, generated by Jim Zimbelman at LPI, Houston, TX