An Earthcache is a special geocache type that adds a geology lesson to the hike. It typically involves a visit to and a study of a special geological feature. To be honest, I haven't been doing very many Earthcaches because I'm not that interested in geology, which is ironic considering the nature of some of my investments. But I trust that those companies have expert geologists on staff to figure out which rocks are likely to hold oil, natural gas, coal, and base metals. :)
For quite a while, there was an Earthcache listed just a few miles north from home. This afternoon, since the weather was good and I had nothing better to do, I went to check it out. It is the Monsey Glen Earthcache at Monsey Glen Park in Monsey. (track log on Google Earth) The coordinates provided were for the parking area. Fortunately, I'd been there before for a regular cache, so I knew approximately which way to go to find the stone steps and rock shelters mentioned in the Earthcache description.
When I got to the far side of the park, I met up with someone who was looking for the rock shelters. So I pointed him to those. He wasn't terribly impressed though and indeed, the shelters aren't very big. The Munsee tribe (after whom the town of Monsey was named) was reputed to have used the shelters but unless they were 3 feet tall, I don't see how more than a few of them could fit in there at the same time. I also took a look at the steps that were carved into the sandstone before leaving to get lunch.