This is a Magellan radar image mosaic of Venus centered on 30 degrees south, 9 degrees east. This scene is approximately 600 kilometers (360 miles) across and includes data from orbits 522 through 561, acquired on October 5-10, 1990. The bright terrain unit is the southeastern portion of Alpha Regio, a mountainous, highly fractured region. The complex fracture and deformation history of Alpha Regio is responsible for the intricate pattern of ridges and valleys. To the south and east these highlands have been flooded and embayed by dark, smooth plains material which apparently formed by extensive eruptions of basalt-like lavas. Several lava flow channels are visible at bottom center. Volcanically embayed remnants of Alpha Regio can be seen as isolated patches. Within these dark plains occur eight rounded "pancake'' domes up to 35 kilometers (20 miles) across and up to 1 kilometer (0.6 mile) high clustered at right center and at bottom right. Several of these domes have fractured and pitted summits. The shapes of these broad flat domes suggests they formed from the extrusion of lavas considerably more viscous (sticky) than those that formed the dark plains.
