English: Ubastet Fluctus — lava flows about 500km across on Venus originating from Derceto Corona (beyond the left boder of the image; previously called Ammavaru caldera). Vertical feature in the bottom left is Vaidilute Rupes (a map of this region). Radar image from the Magellan probe.

Caption from NASA photojournal: This is a 225 meter per pixel Magellan radar image mosaic of Venus, centered at 47 degrees south latitude, 25 degrees east longitude in the Lada region. The scene is approximately 550 kilometers (341 miles) east-west by 630 kilometers (391 miles) north-south. The mosaic shows a system of east-trending radar-bright and dark lava flows encountering and breaching a north-trending ridge belt (left of center). Upon breaching the ridge belt, the lavas pool in a vast, radar-bright deposit (covering approximately 100,000 square kilometers [right side of image]). The source caldera for the lava flows, named Ammavaru, lies approximately 300 kilometers (186 miles) west of the scene.