Florissant Fossil Beds National Monument

Florissant Fossil Beds National Monument
Hornbek Homestead at Florissant Fossil Beds National Monument
Florissant Fossil Beds National Monument

An early settler from Florissant, Missouri named this area after his hometown. 34 to 35 million years ago, this valley was dominated by Lake Florissant, averaging 1 mile in width and stretching 12 miles through an ancient forested valley. Lush ferns and shrubs lived beneath redwoods, pines, cedars and a mixed-hardwood forest. There were thousands of insects in the humid climate. Mollusks, fish, birds and mammals lived in or around the lake. Again and again volcanic mudflows blanketed parts of the valley, one of them responsible for the creation of the lake. Every time the volcano erupted it showered the area with tons and tons of ash and pumice. Each rainfall washed the fine ash into the lake where it slowly covered the remains of creatures that died and sank to the bottom. Eventually those sediments were compacted and became shale, fossilizing the buried remains.

Today, Florissant Fossil Beds National Monument preserves this internationally renowned site. More than 50,000 specimens have been collected by paleontologists working here. As much as a lot of that ancient lake life is preserved here, very little of the other forms of life that inhabited the area are preserved: Unless a bird or mammal died in or near the lake, its chances of preservation were very slim.

A historic barn at Florissant Fossil Beds National Monument
Map of Florissant Fossil Beds National Monument
Florrissant Fossil Beds
National Monument map

The remains of prehistoric plants and animals found here are relatively young in geologic terms. The fossils found at Florissant have much to say about life in the late Eocene Epoch, about 30 million years after the last of the dinosaurs and about 33 million years before the first humans. Most of the fossils found here are studied and kept at various universities and museums, with a few displayed in the park visitor center. Unfortunately, many others were taken as souvenirs over the years and the knowledge they may have imparted was lost. The park now protects millions of undisturbed fossils and allows a limited number to be excavated for study each year.

Fossils of more than 140 species of plants have been found at Florissant. These consist mostly of leaves but twigs, cones, seeds, flowers and pollen grains have also been found. There are also massive petrified stumps of giant redwood trees where volcanic mudflows buried them millions of years ago. The record in the stone suggests that the ancient forest was unlike any now in Colorado. Trees and shrubs grew here whose closest living descendants are now found in the southeastern United States, Mexico and China.

While insects are usually too fragile to be preserved as fossils, the fine volcanic ash did such a good job here that many thousands of insect fossils have been recovered from the shale. More than 1400 species have been described from the findings so far. The fossils show that the insects of 34-35 million years ago were very similar to today''s, however, many types that are found here no longer exist in Colorado. Some, like the tsetse fly, no longer live in North America and many others are extinct.

The bottom of the ancient lake bed at Florissant Fossil Beds National Monument

Fossils are studied in the context in which they are found and as one element in a community of organisms. Some of the insect fossils are found coupled with the leaves that they lived on. Because of this relationship, every fossil can serve as a key to unlock ancient knowledge. As most of the remains found here date from the Eocene Epoch, Florissant Fossil Beds serves as a wonderful repository of information. In the Eocene Epoch, mammals emerged as the dominant land animals on the planet. They also took to the air and the sea. The many variations included some of the earliest giant mammals. The fossil record reveals many mammals unlike anything seen today. However, as time went on and evolution continued, the forest plants, freshwater fish and insects became much more like those we know now.

From Labor Day to Memorial Day, Florissant Fossil Beds National Monument is open from 9 am to 5 pm daily except on Thanksgiving, Christmas and New Year''s Days. From Memorial Day to Labor Day the hours are 8 am to 6 pm, every day. Entry fees: $3 per person for ages 16 and up, good for seven days from date of purchase. Younger folks get in free. Fees can only be paid by cash or check, no credit or debit cards. Florissant Fossil Beds National Monument is a day-use only property, no camping is allowed. The Monument offers 14 miles of hiking trails including two self-guided trails that begin in the outdoor exhibit area behind the Visitor Center. There is a picnic area at the Visitor Center and another on Lower Twin Rock Road.

Plant fossils found at Florissant Fossil Beds
Plant fossils found at Florissant Fossil Beds
Insect fossils found at Florissant Fossil Beds
Insect fossils
Fossil images and small map from the Florissant Fossil Beds Official Map and Guide
Other photos courtesy of TheArmchairExplorer, CCA-by-SA 4.0 License

Geologic Time Scale

A view of the actual K-T Boundary embedded in the sandstone near Trinidad, Colorado
The K-T Boundary is that white band beneath the upper layer of sandstone
Subdivisions based on Strata/Age Radiometric Dates (millions of years ago)
Neogene 0-2
Paleogene 2-65
Laramide Orogeny 63-65
Cretaceous-Tertiary Extinction Event 65
Cretaceous 65-145
Jurassic 145-210
Triassic 210-255
Permian-Triassic extinction event 251-260
Permian 255-280
Alleghenian Orogeny 260-325
Carboniferous: 280-360
Pennsylvanian 280-320
Mississippian 320-360
Devonian 360-415
Silurian 415-465
Ordovician 465-520
Cambrian 520-540
Precambrian Eons 541-4600
Proterozoic 541-2,500
Archean 2,500-4,000
Hadean 4,000-4,600

The table to the right gives a rough breakdown of the geological ages of Earth as used in modern Geology texts.

Much of the oil and gas we use comes from vegetative deposits made during the Permian and Pennsylvanian (late Carboniferous) ages. A lot of the coal we use (with its accompanying methane gas) comes from the great jungles and forests of the Mississippian and Pennsylvanian (early and late Carboniferous) ages in the Paleozoic era. Big reptiles and dinosaurs lived out their lives during the Triassic, Jurassic and Cretaceous Periods of the Mesozoic Era.

It was at the end of the Cretaceous Age that the Laramide Orogeny was set in motion, the Colorado Plateau uplifted and the Ancestral Rocky Mountains built. That was also during the time when an asteroid impacted near the Yucatan Peninsula and tipped the environmental scale in a direction that wiped virtually all the dinosaurs from the face of the planet. The K-T Boundary is a thin layer of iridium that filled the atmosphere during that explosion, then fell back to Earth during the global fires and the atmospheric upheaval afterward. While there have been plenty of marine, insect, reptile, amphibian, plant and mammal fossils found from times since, there has never been a dinosaur fossil found from the years after that impact. The K-T boundary is accepted as the definitive marker between the Cretaceous and Tertiary Ages, the marker of the Jurassic extinction event.

The Permian-Triassic extinction event seems to have happened in two major pulses about 9 million years apart. During the Permian age many insect orders had grown huge. A rise in CO2 in the atmosphere led to a rise in temperature and to acidification of the oceans. Marine invertebrates with carbon-based skeletons suffered worst but this was also the only mass extinction that affected insects: eight or nine insect orders became extinct and ten more suffered greatly reduced diversity. Insects, however, had generally recovered by the late Triassic, everything but that giant size anyway. The second pulse seems to have occurred around the time of the Araguainha impact, an asteroidal impact in Brazil that was not large enough to set off catastrophic extinction by itself but it occurred in an area filled with oil shale and the resulting sudden rise in global warming from the fires that ignited may have begun the atmospheric cascade that led to ocean surface temperatures around 104°F (40°C). That high an ocean temperature meant it was too hot for many marine species to survive. When it was over, more than 70% of terrestrial species and almost 90% of marine species had died out. Some land ecosystems took 30 million years to recover.

Photo of the K-T Boundary courtesy of TheArmchairExplorer, CCA-by-SA 4.0 License