Hiking along a ridgetop above the wind-rippled surface of Flathead Lake, I approached a rock outcrop. From a distance of a couple hundred yards, the rock looked barren, if a bit weathered. But on closer inspection, I found the weathering to be actually a lichen covering the surface of this rock. This lichen was thin, not much thicker than a few notebook pages, and it was tightly attached to the rock surface. A mottled grayish-green color, it felt nubbly, like running your hand over crushed velour. Because of the lichen, I couldn’t easily determine the rock type or what its color or texture was. I’m just an amateur, but even professional geologists can be frustrated by the growth of lichens because they obscure so much valuable geologic information. But in fact, lichens, while masking the surface, can actually reveal what lies beneath that surface within the solid rock. …

This Field Note was written by Ron Tschida. Would you be interested in writing one? Contact Allison De Jong, Field Notes editor, at adejong [at] montananaturalist [dot] org or 406.327.0405. Please visit the Field Notes website at the Montana Natural History Center for more information.