The article says that if the earth were a little less massive it probably wouldn't be geologically active. That seems unlikely to me. Even without plate tentonics we would still have shield volcanoes forming over hotspots. And the weight of the material they add to the surface would push the crust down into the mantle. The process could result in a cycling of materials through the crust without plate tentonics. One question I have would be are worlds without plate tentonics prone to periods of extreme volcanism as Venus might be? And would this merely be increased volcanism over tens of millions of years that in general would allow life to go on as normal or would they be rapid, Permian extinction type events?