Erosion is most important on earth, because earth also has liquid water which causes much erosion. The atmosphere of Venus, which is very dense and composed mostly of carbon dioxide, is highly opaque to infrared light. Sunlight penetrates relatively far down into the atmophere, heating the lower layers. These layers then give off infrared light which is trapped by the upper layers. Because it is so hard for heat to escape from the lower atmosphere, it becomes very hot, heating the surface as well.
Volcanic activity is caused by heat, below the surface, trying to escape.
In earth, this heat builds up slowly from radioactive decay of elements like uranium. This process occurs on our moon as well, but since the moon is so much smaller than earth, the heat doesn't build up enough to cause any volcanic activity. Io also gets squeezed in the sideways direction, because of the converging gravitational pulls toward Jupiter's center. As Io's eccentric orbit carries it toward and away from Jupiter about every two days, the tidal forces become stronger and weaker, creating friction from the constantly varying forces. Titan is the only moon in the solar system with a significant atmosphere.