Notes: Seven circular domes can be seen on the eastern edge of Alpha Regio. They average 25 km (15 mi) in diameter with maximum heights of 750 m (2475 ft). 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 thedomes suggests that lava welled up inside the domes, causing the surface to stretch.