Earthcaches feature geology. There is usually no physical cache. Instead, the cacher is asked to answer a series of questions about a geological formation. The coordinates of the cache lead to an example of the geological formation in question.
Earthcache Day is usually in August, a blazingly hot month in Texas. To log our find for Earthcache Day 2014, Sweetieheart and I left home at 6:30AM; we left the site by 10:30AM when temperatures were already in the high 90s.
We had to find examples of North Texas fossils and answer some questions about the bed where we found these fossils. We made our find!