Have you ever tried geocaching?
Geocaching is a real-world outdoor treasure hunting game. Players try to locate hidden containers, called geocaches, using GPS-enabled devices and then share their experiences online.
In Earthcaching, instead of looking for a hidden container, you look for earth science. An Earthcache is an educational form of a virtual cache. The reward for these caches is learning more about the planet on which we live - its landscapes, its geology or the minerals and fossils that are found there. Earthcaches are developed in association with the Geological Society of America. For more information go to http://www.geosociety.org/earthcache/
Here is an example, in Oak Park you can find the location of the Prehistoric Continental Divide Earthcache.
The person who created the earthcache includes a link to a web page that explains this geological formation.