Sacajawea Patera Sacajawea Patera is a huge caldera located in western Ishtar Terra. The caldera is bounded by a zone of graben and fault scarps. Domical Hills Seven circular domes can be seen on the eastern edge of Alpha Regio. Some scientists believe they are the result of eruptions of thick lava that flowed from a vent on level ground, resulting in an even lateral pattern of lava. The concentric and radial fracture pattern on the surface of the domes suggests that lava welled up inside the domes, causing the surface to stretch.
Shield volcanoes form when hot, fluid lava erupts non- explosively.
The radar-bright area in Eistla Regio consists of both the summit and radial troughs and scarps extending to the northeast down the slope of Gula Mons. Regional expansion of the crust is obvious in this area because of the presence of graben. Golubkina The Magellan image of Crater Golubkina. The terraced inner walls take shape late in the formation of an impact crater, due to the collapse of the initial cavity created by the meteorite impact. The central peak forms due to the rebound of the inner crater floor.