[super2009]

What has been the dominant geological process on Venus for the last billion years? What is the dominant rock type found on the surface due to this geological process?

[ebaines]

From Wikipedia
Geology of Venus - Wikipedia, the free encyclopedia

It is theorized that Venus underwent some sort of global resurfacing about 300-500 million years ago, which is the approximate age of much of the surface of the planet. Although it is exciting to imagine the entire crust of Venus sinking into the mantle, it is probably more reasonable to discuss massive lava flows lasting thousands to millions of years.

One possible explanation for this event is that it is part of a cyclic process on Venus. On Earth, plate tectonics allow for the escape of heat from the mantle. However, Venus has no evidence of plate tectonics, so the theory is that the interior of the planet heats up (due to the decay of radioactive elements) until material in the mantle is hot enough to force its way to the surface. The subsequent resurfacing event covers most or all of the planet with lava, until the mantle is cool enough that the process starts over.