Easy/Moderate Hike. Join volunteer naturalists for a 1.3-mile moderate hike along the Lichen Loop Trail to learn how this landscape has changed. Tales told in the rocks span 200 million years, from ancient sand dunes to tidal flats to riverbeds where dinosaurs roamed. Registration for most programs begins on the 20th of the month before the event. Registration required. Register Registration is required through Discover Boulder County, Parks & Open Space’s volunteer and event registration system. If you’re new to the system, you'll need to create an account. But it’s easy and we only use your contact information to communicate about events you register for. We will never sell or give your information to a third party.