The Florissant Fossil Beds

The Florissant Fossil Beds National Monument in Central Colorado is home to some of the most exceptionally preserved fossils from 34 million years ago. These fossils have been preserved because of the interaction of volcanic ash from the nearby Thirtynine Mile volcanic field with diatoms in a large, freshwater lake, causing an diatom bloom. As the diatoms fell to the bottom of the lake, any plants or animals that had recently died were preserved by the diatom falls. Many types of ancient flora and fauna have been found in the Florissant Fossil Beds, including over 1,500 species of insects and aracnids alone. The preservation of these animals gives insight into the environment that they survived in, as well as some aspects of their behavior.

Source: National Park Service