This rock cairn contains each principal rock type (igneous, metamorphic, sedimentary) as well as representatives of each major division of geologic time (Precambrian, Paleozoic, Mesozoic, Cenozoic).

Ginkgos are "living fossils" because they have existed throughout much of geologic time without going extinct. In fact, they go all the way back to the Paleozoic. This particular fossil ginkgo is Paleocene in age (about 55-65 million years old) and is surrounded by modern ginkgo leaves. Thanks to Greg Retallack for providing the fossil!

These pieces of ice are running out of time... melting, just like Earth's glaciers are today. Geologists have been warning us about global warming for more than two decades and our politicians are only now beginning to understand. Sigh...