@Minh:

Tidal forces, tectonic activity.

Here are some articles : http://www.scientificamerican.com/article.cfm?id=moon-life-tides , http://www.astrosociety.org/education/publications/tnl/33/moon2.html , http://www.astronomytoday.com/astronomy/earthmoon.html

The minerals that form the planet also matter, its not a given that just because the planet is within the Goldilocks zone and is small that its Earth-like.