Venus

Not all volcanic activity involves volcanoes. Many volcanic deposits on the rocky planets were produced by flood lavas, large-volume eruptions that covered vast areas. The lava usually poured out of vents now buried in low-lying areas, such as impact basins and craters.  

Over 80% of Venus is covered by relatively young volcanic plains, less than 500 million years old. The abundance of these plains suggests that Venus may have experienced catastrophic volcanic events that caused lava to flood large parts of its surface. Image courtesy of NASA.