Fossil Butte National Monument is located 15 miles (24 km) west of Kemmerer, Wyoming, United States. It centers on an extraordinary assemblage of Eocene Epoch (56 to 34 million years ago) animal and plant fossils associated with Fossil Lake—the smallest lake of the three great lakes which were then present in what are now Wyoming, Utah, and Colorado. The other two lakes were Lake Gosiute and Lake Uinta.
Fossil Butte National Monument preserves the best paleontological record of Cenozoic aquatic communities in North America and possibly the world, within the 50-million-year-old Green River Formation — the ancient lake bed. Fossils preserved — including fish, alligators, bats, turtles, dog-sized horses, insects, and many other species of plants and animals — suggest that the region was a low, subtropical, freshwater basin when the sediments accumulated, over about a 2 million-year period.
Map of Seasonal and Year-Round BLM Public Land User Limitations in the BLM Kemmerer Field Office area in Wyoming. Published by the Bureau of Land Management (BLM).
Official Brochure of Fossil Butte National Monument (NM) in Wyoming. Published by the National Park Service (NPS).
https://www.nps.gov/fobu/index.htm
https://en.wikipedia.org/wiki/Fossil_Butte_National_Monument
Fossil Butte National Monument is located 15 miles (24 km) west of Kemmerer, Wyoming, United States. It centers on an extraordinary assemblage of Eocene Epoch (56 to 34 million years ago) animal and plant fossils associated with Fossil Lake—the smallest lake of the three great lakes which were then present in what are now Wyoming, Utah, and Colorado. The other two lakes were Lake Gosiute and Lake Uinta.
Fossil Butte National Monument preserves the best paleontological record of Cenozoic aquatic communities in North America and possibly the world, within the 50-million-year-old Green River Formation — the ancient lake bed. Fossils preserved — including fish, alligators, bats, turtles, dog-sized horses, insects, and many other species of plants and animals — suggest that the region was a low, subtropical, freshwater basin when the sediments accumulated, over about a 2 million-year period.
In the ridges of southwest Wyoming are some of the best-preserved fossils in the world. They tell the story of ancient life in a warm, wet environment in and around a freshwater lake. Stingrays swam in the lake. Turtles basked in the sun. Leaves rustled in the breeze while early horses darted between the trunks. We reveal more of the past with each fossil found.
By car: Travel 9 miles west of Kemmerer, Wyoming on U.S. Highway 30. There is a highway sign near mile post 44; turn right onto Lincoln County Road 300. The Historic Quarry Trail is approximately 1/2 mile on the right. Continue west on County Road 300 for approximately 1.5 miles to Chicken Creek Road which provides access to the visitor center, scenic drive, Nature Trail and picnic area. Closest airports: Rock Springs, Wyoming (130 miles); Salt Lake City, Utah (150 miles).
Fossil Butte Visitor Center
Over 2000 fossils are on exhibit. Video programs feature what scientists have learned from the fossils and the rocks they're found in, and how fossils are excavated and prepared. Visitor Center hours vary by the season.
By Car: Travel 9 miles west of Kemmerer on U.S. Highway 30 following the highway signs. Near mile post 44 there is a sign for Fossil Butte National Monument; turn right on Lincoln County Road 300. Continue for approximately 3 miles before turning right on Chicken Creek Road. Continue for one mile. Parking is available for private vehicles, buses and RV/trailers.
Fossils on the Ridge
Fish fossils, Knightia eocaena, exposed near cliff
Knightia eocaena, the most abundant vertebrate fossil in the world, lies exposed near cliff face.
Cockerellites liops, a Common Fossil Fish
a well preserved fossil fish, Cockerellites liops
Fossils from the Green River Formation are known for their excellent preservation, abundance, and diversity. Cockerellites liops is one of the common fishes found here.
Palm Frond
fossil palm frond
Fossil palm fronds and other plants indicate a climate similar to the Gulf Coast states.
The Limestone Ridges, Remnants of Ancient Fossil Lake, Contrast the Green, Early Summer Landscape.
A scenic view of Fossil Basin in early summer; yellow limestone, red mudstones and green vegetation
Early Summer Beauty in the High Desert of Southwestern Wyoming
Visitor Center
visitor center with Fossil Butte in the background
The visitor center is nestled in a sagebrush landscape beneath Fossil Butte. Over 300 fossils are on exhibit.
Moonrise Over Fossil Butte
The moon rises just to the right of snow-covered Fossil Butte.
Fossil Butte is the most noticeable landmark of the park and where the monument got its name.
Grand Teton National Park Fire Management Program Transfers Fire Engines to Rural Wyoming Fire Districts
Grand Teton National Park Fire Management Program Transfers Fire Engines to Rural Wyoming Fire Districts
Fire engine on a trailer ready to be transported
Landbird Monitoring in Northern Colorado Plateau Network Parks, 2018
Because birds can be sensitive to habitat change, they are good indicators of ecosystem integrity. The Northern Colorado Plateau Network partners with the University of Delaware to assess breeding-bird species trends in three different habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Find out which species were increasing and declining at network parks as of 2018.
Small, bright-orange bird with yellowish underfeathers.
Wildland Fire in Sagebrush
Sagebrush will burn when the surrounding grasses are dry. With strong winds, fire spreads rapidly with flames sometimes reaching over 30 feet high. While fire easily kills sagebrush, the other plants resprout from protected roots producing lush forage for wildlife and livestock.
Close-up of sagebrush leaves
What We’re Learning and Why it Matters: Long-Term Monitoring on the Northern Colorado Plateau
Knowing which key natural resources are found in the national parks, and whether they're stable or changing, helps decisionmakers make sound choices. The Northern Colorado Plateau Network is building that knowledge. After more than ten years of monitoring, we've learned a lot about park ecosystems, how they're changing, and what they may look like in the days to come. Find out what we’ve learned and how it’s being used to help managers plan for the future.
Man stands in a stream, looking down at a handheld gauge.
Landbird Population Trends in the Northern Colorado Plateau Network, 2019
Because birds can be sensitive to habitat change, they are good indicators of ecosystem integrity. The Northern Colorado Plateau Network partners with the University of Delaware to assess breeding-bird species trends in three different habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Find out which species were increasing and declining at network parks as of 2019.
Bald eagle
NPS Geodiversity Atlas—Fossil Butte National Monument, Wyoming
Each park-specific page in the NPS Geodiversity Atlas provides basic information on the significant geologic features and processes occurring in the park. Links to products from Baseline Geologic and Soil Resources Inventories provide access to maps and reports.
park landscape
Cenozoic Era
The Cenozoic Era (66 million years ago [MYA] through today) is the "Age of Mammals." North America’s characteristic landscapes began to develop during the Cenozoic. Birds and mammals rose in prominence after the extinction of giant reptiles. Common Cenozoic fossils include cat-like carnivores and early horses, as well as ice age woolly mammoths.
fossils on display in a visitor center
Landbird Population Trends in the Northern Colorado Plateau Network, 2020
Because birds can be sensitive to habitat change, they are good indicators of ecosystem integrity. The Northern Colorado Plateau Network partners with the University of Delaware to assess breeding-bird species trends in three different habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Find out which species were increasing and declining at network parks as of 2020.
Small beige bird with black beak and feet, brown back.
Monitoring From Space: Using Satellite Imagery to Measure Landscape Conditions on the Ground
Scientists from the Northern Colorado Plateau Network travel thousands of miles each year to collect data on plants, soils, and water across network parks. But it would be impossible to cover every square inch of the Northern Colorado Plateau with boots on the ground. Instead, we simultaneously monitor the parks with boots in space—satellite data that provide information at a much broader scale.
Satellite and Earth in space
Localized Drought Impacts on Northern Colorado Plateau Landbirds
Birds of the desert southwest, a climate-change hotspot, are among the most vulnerable groups in the US. To help park managers plan for those changes, scientists evaluated the influence of water deficit on landbird communities at 11 national parks in Utah and Colorado. The results will help land managers to focus conservation efforts on places where certain species are most vulnerable to projected climate changes.
A man wearing a clipboard looks through binoculars at dawn in field of sagebrush
Changing Patterns of Water Availability May Change Vegetation Composition in US National Parks
Across the US, changes in water availability are altering which plants grow where. These changes are evident at a broad scale. But not all areas experience the same climate in the same way, even within the boundaries of a single national park. A new dataset gives park managers a valuable tool for understanding why vegetation has changed and how it might change in the future under different climate-change scenarios.
Green, orange, and dead grey junipers in red soil, mountains in background
Landbird Population Trends in the Northern Colorado Plateau Network, 2021
Because birds can be sensitive to habitat change, they are good indicators of ecosystem integrity. The Northern Colorado Plateau Network partners with the University of Delaware to assess breeding-bird species trends in three different habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Find out which species were increasing and declining at network parks as of 2021.
Small dove with black spots on back of wings, long tail, and brownish-gray body.
Volcanic Ash, Tephra Fall, and Fallout Deposits
Volcanic ash, pumice, and tephra ejected in volcanic eruptions ultimately falls back to Earth where it covers the ground. These deposits may be the thin dustings or may be many tens of feet (meters) thick near an eruptive vent. Volcanic ash and tephra can present geohazards that are present great distances from the erupting volcano.
photo of a bluff with exposed fine-grained volcanic ash and pumice.
Invasive Exotic Plant Monitoring at Fossil Butte National Monument
Invasive exotic plants are one of the most significant threats to natural resources in the national parks today. To provide early warning of weed invasions, the Northern Colorado Plateau Network monitors target plants in park areas where they are likely to first establish: along roads, trails, and waterways. Find out what we've learned at Fossil Butte National Monument.
Tall green grass with seedy tufts.
Series: Geologic Time—Major Divisions and NPS Fossils
The National Park System contains a magnificent record of geologic time because rocks from each period of the geologic time scale are preserved in park landscapes. The geologic time scale is divided into four large periods of time—the Cenozoic Era, Mesozoic Era, Paleozoic Era, and The Precambrian.
photo of desert landscape with a petrified wood log on the surface
Making an Impact: Long-Term Monitoring of Natural Resources at Intermountain Region National Parks, 2021
Across the Intermountain Region, Inventory & Monitoring Division ecologists are helping to track the effects of climate change, provide baseline information for resource management, evaluate new technologies, and inspire the next generation of park stewards. This article highlights accomplishments achieved during fiscal year 2021.
A man looks through binoculars at sunrise.
Landbird Population Trends in the Northern Colorado Plateau Network, 2022
Because birds can be sensitive to habitat change, they are good indicators of ecosystem integrity. The Northern Colorado Plateau Network partners with the University of Delaware to assess breeding-bird species trends in three different habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Find out which species were increasing and declining at network parks as of 2022.
Hairy woodpecker clings to the underside of a tree branch.
A Changing Bimodal Climate Zone Means Changing Vegetation in Western National Parks
When the climate changes enough, the vegetation communities growing in any given place will also change. Under an expanded bimodal climate zone, some plant communities in western national parks are more likely to change than others. National Park Service ecologists and partners investigated the future conditions that may force some of this change. Having this information can help park managers decide whether to resist, direct, or accept the change.
Dark storm clouds and rainbow over mountains and saguaros.
Updated Species Database Will Help Boost Amphibian Conservation Across the National Park Service
To steward amphibians effectively, managers need basic information about which species live in parks. But species lists need constant maintenance to remain accurate. Due to recent efforts, the National Park Service now has an up-to-date amphibian species checklist for almost 300 parks. This information can serve as the basis for innumerable conservation efforts across the nation.
A toad sits on red sand, looking into the camera.
Landbird Population Trends in the Northern Colorado Plateau Network, 2023
Because birds can be sensitive to habitat change, they are good indicators of ecosystem integrity. The Northern Colorado Plateau Network partners with the University of Delaware to assess breeding-bird species trends in three different habitats: low-elevation riparian, pinyon-juniper, and sage shrubland. Find out which species were increasing and declining at network parks as of 2023.
A speckled white bird floats on blue water.
How Pollinator Inventories Can Inform Park Management Decisions
Pollinators play a crucial role in national park ecosystems and beyond. In the national parks, species inventories help managers know which pollinators are present, and in what abundance, to better understand the state of park ecosystems and make decisions about how to manage them. From 2024 to 2026, 17 parks across the country will be surveyed for bees and butterflies.
Bee laden with pollen sits atop a purple flower.
Project Profile: Produce Seed for Intermountain Grasslands and Restore Intermountain Central Grasslands
The National Park Service will restore grassland ecosystems in select national parks in Arizona and Colorado to advance landscape conservation actions, mitigate the overall loss of these systems, and build a strong core of healthy grasslands to benefit the species and communities who rely on them. The process includes collecting and increase native seed for restoration in central grasslands, supporting the National Seed Strategy.
A tan grassland with trees in the forefront and two mountains in the background.
Landbird Population Trends in the Northern Colorado Plateau Network, 2024
Northern Colorado Plateau Network’s long-term landbird monitoring program provides habitat-based updates for bird population status and trends in the parks in the Northern Colorado Plateau. These inform scientists and managers about changes in bird populations and about the health of the habitats they depend on. Learn more about which species were detected in the network parks for the first time and which landbird populations were increasing or declining between 2005 - 2024.
A bird sitting in a tree.
Fossil Butte
National Park Service
U.S. Department of the Interior
National Monument
Wyoming
Creating a Fossil Record
An enormous western landscape surrounds
Fossil Butte. Long slopes rise to broadbacked ridges where the earth's rock crust
reflects against the sky. Cattle graze huge
ranges of hardy, native grass. Exposed and
almost treeless, the surface barely conceals
a wealth of coal, phosphates for fertilizer,
and oil-producing shale.
tending north and south are expressions of
a long period of mountain building before
which most of the western United States
was submerged beneath the sea. Basins
between the ridges where the earth buckled
downward collected millions of years worth
of eroded gravel and rock debris washed
and weathered from higher ground.
The contrast from a semi-arid land of such
bold proportions to the delicate tracings of
prehistoric fishes makes Fossil Butte even
more exquisite. Perhaps some of the first
to discover the hundreds of varieties of fossils here more than a century ago sensed
the same thing as they began to collect and
study the fish.
When the land heaved again, mountain
ridges were rejuvenated; the basins sank
further, collected water, and became lakes.
In the warm humid air, large palms, ferns,
and cinnamon trees sheltered the ancestors
of modern mammals. Horses no bigger than
today's dogs, primitive monkeys, and the
ponderously built ancestors of the rhinoceros and elephant lived in an environment
of mountains and valley, all in a subtropical
setting.
Although significant questions remain to be
answered, succeeding generations of scientists have given us most of the geological
story of ancient Fossil Lake, of which the
park today is a small part. The ridges ex-
dant was the life in the water and near the
shore of Fossil Lake. Crocodiles and turtles
basked in the sun. Snakes, lizards, clams,
snails, and small free-swimming shellfish
concentrated at water's edge. Within the
lake swam large numbers of fish, many of
them closely related to the perch, herring,
and stingray of today. This healthy Eocene
environment changed abruptly four times.
The Fossil Lake itself dried up each time.
Fish died in great numbers during the life
of the lake and settled undisturbed into the
lake bottom. Nor did millions of years disturb their frail shapes. Blankets of sediment
gradually turning to hard rock kept intact
their skeletons, their delicate fins and tail
rays, and even their scales.
Such was the terrestrial life of the Eocene
Epoch 50 million years ago. No less abun-
The Process of Fossilization
Normally, a living thing
rapidly begins to decay soon after death.
In ancient Fossil Lake,
however, the great
depth of the lake, the
presence of calcium
carbonate on the bottom, and the thermal
stratification that occurs in lakes of warm
temperate climates all
contributed to preserving fish, plants, and
other fossils
Thermal stratification
simply means that a
cool layer rests below
a warmer layer on the
surface and little mixing occurs. The surface layers are much
warmer, lighter, and
less viscous than the
deeper, cooler waters.
Winds supply oxygen
to the surface layers,
but are unable to penetrate and circulate
the deep waters. The
decay of organic matter at the lake bottom
uses up all the available oxygen and produces hydrogen sulfide and carbon dioxide, both toxic to most
living organisms.
The lack of suitable
living conditions prevents many small predatory creatures from
disturbing any material
on the lake bottom. In
addition, the lack of
oxygen may slow the
decomposition process, allowing the dead
organisms to be covered before any great
degree of decay occurs.
During the spring and
early summer algal
blooms in the surface
waters consume carbon dioxide during
the production of food.
The removal of the
carbon dioxide makes
the water more alkaline. But in the fall
the algae die and this
organic matter slowly
settles to the bottom,
where it ferments and
decays As oxygen is
consumed in the process, more carbon dioxide is given off and
the water becomes
somewhat acid. This
action, in turn, causes
some of the carbonate
mud present on the
bottom to redissolve.
This dissolved mud is
the protective coating
into which the dead
fish sink. It seals them
into the bottom with
the other sediments
and the actual process
of fossilization begins.
In time great pressure
changes layers of sediments into laminated
limestone containing
a fossil record —a record that is viewed millions of years later by
paleontologists who
are trying to piece
together the vast puzzle of life 50 million
years ago.
Today's landscape gives no clue to its appearance millions of years ago. Here the imagination must run rampant to recreate that long
ago scene.
"The chemicals that composed the fish—most of them at least—are still there in the stone.
They are, in a sense, imperishable. They may come and go, pass in and out of living
things, trickle away in the long erosion of time. They are inanimate, yet at one time they
c