The Department of Geological Sciences at SDSU is doing a major service for the geological community by providing some excellent geology-themed kml files. The word needs to spread.Go to their site and look for your favorite topic. Who couldn't like this stuff?

http://www.geology.sdsu.edu/localgeology/getour.html

There are an array of useful geology images in addtion to some other, practical datasets. For example, the link below is to a Google Earth file showing the extent, name, and index number of every 7.5 topographic quad in the US. It can be bulky if you leave all of the data turned on, but is useful nonetheless.

http://www.geology.sdsu.edu/localgeology/gekmz/maps_overlays/drg_dem_index/24...