Introduction
Fossils that are in situ have great scientific importance because the rocks or deposits in which they are embedded provide essential information about the life and/or death of the organism, and the processes that occurred during fossilization.
There is also something extra special about seeing fossils in situ as it provides a unique encounter with the natural world. A park visitor may experience the thrill of discovery when seeing a fossil encased in bedrock or encountering an unexpected fossil along a trail.
The following 17 parks contain in situ fossils that are readily viewable either along interpretive trails, exposed at quarry sites, or on ranger-led tours.
There is also something extra special about seeing fossils in situ as it provides a unique encounter with the natural world. A park visitor may experience the thrill of discovery when seeing a fossil encased in bedrock or encountering an unexpected fossil along a trail.
The following 17 parks contain in situ fossils that are readily viewable either along interpretive trails, exposed at quarry sites, or on ranger-led tours.
Agate Fossil Beds National Monument, Nebraska
A different and very unusual kind of fossil can be visited at Agate Fossil Beds National Monument. The Daemonelix Trail near the west monument boundary leads to exposures of one of the most intriguing trace fossils in the history of North American paleontology. They were studied more than a decade before Agate’s bone beds were first excavated in 1904.
These spiral-shaped Miocene-age fossils, also known as “Devil’s corkscrews,” puzzled paleontologists for decades. Some thought they were enormous roots or even sponges, until the fossil remains of the dry-land beaver Palaeocastor were recovered in one, showing they were really burrows. The burrows had a nesting chamber at the bottom and it is thought that their shape helped keep floodwaters out and maintain a more consistent temperature and humidity.
The Daemonelix Trail is a mile long. The burrows are in protective cases because the soft sediment they are in is highly erosive.
The historic fossil quarries in the monument were heavily excavated in the early 20th century and the fossil-producing beds are not currently exposed. But the hills containing the quarries can be visited on the Fossil Hills Trail.
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Big Bend National Park, Texas
The Santa Elena Canyon Nature Trail is one of the best places in the park to see fossils. The 1.6-mile roundtrip trail is also one of the most scenic short trails in the park. Trailside signs point out marine invertebrate fossils in the limestone canyon walls.
Additionally, a large ammonite is located within the trail surface of the Hot Springs Trail, and fossil oysters are visible in the trail tread of the Rio Grande Overlook and Trail.
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Craters of the Moon National Monument & Preserve, Idaho
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NPS—Volcanoes and Fossils
Delaware Water Gap National Recreation Area, Pennsylvania
Delaware Water Gap National Recreation follows the Delaware River through Paleozoic rocks, and many fossils of marine invertebrates have been found there. The Fossil Trail, located at Pocono Environmental Education Center in Delaware Water Gap, leads to several rock outcrops containing marine invertebrate fossils such as trilobites, brachiopods and crinoids. During the Devonian Period, about 370 million years ago, this area near the Pennsylvania–New Jersey border was under a shallow continental sea.
The Pocono Environmental Education Center (PEEC) is a private nonprofit organization that is the education partner of Delaware Water Gap National Recreation Area. The Fossil Trail is a loop that is just over 1 mile in length.
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Dinosaur National Monument, Utah
The Quarry Exhibit Hall in Dinosaur National Monument is one of the premiere places in the world to see dinosaur bones in situ. The wall of bones in the Quarry Exhibit Hall, exposed on a steeply dipping bed of the Late Jurassic Morrison Formation, contains more than 1,500 fossil bones of nine different dinosaur genera as well as other vertebrates. The site of the former Carnegie Quarry was developed so that the public could see bones in place, and the first permanent structure around the fossil-bearing rock slab was completed and opened in 1958. The building was refurbished and rededicated in 2011.
The Fossil Discovery Trail, is a 1.2-mile one-way hike that takes off near the Quarry Exhibit Hall, leads to several dinosaur bone fragments exposed in the Morrison Formation in their natural state (i.e., unexcavated).
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Florissant Fossil Beds National Monument, Colorado
NPS photo by Justin Tweet.
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Volcanoes and Fossils
Grand Canyon National Park, Arizona
NPS Photo by Kristen M. Caldon
Grand Canyon National Park has one of the richest Paleozoic fossil records in the National Park System. Many of the fossils are in rock layers only exposed within the depths of the canyon and are not readily accessible. However, the Kaibab Formation that makes up the rim of Grand Canyon contains marine invertebrate fossils.
The Kaibab Formation is predominately made of limestone and was deposited approximately 270 million years ago. It contains marine invertebrate fossils, such as brachiopods, crinoids, and horn corals. The two best places to see fossils in the Kaibab Formation are at the Bright Angel Fault Fossil Beds on the South Rim and the Bright Angel Point Trail on the North Rim. During the summer, there are sometimes ranger-guided programs to the fossil site on the South Rim.
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Guadalupe Mountains National Park, Texas
Guadalupe Mountains National Park contains one of the world’s finest examples of an ancient reef system. In fact, the mountains are essentially an uplifted and eroded reef that existed for millions of years during the Permian, known as the Capitan Reef. The Capitan Reef is made up of several rock formations that represent different parts of the reef system, and these include many different kinds of marine invertebrate fossils, such as sponges, horn corals, bryozoans, brachiopods, cephalopods, gastropods, trilobites, crinoids, and even sea urchins.The 0.9-mile McKittrick Canyon Nature Trail is the easiest place to see fossils in Guadalupe Mountains National Park, as there are numerous fossils along its path, some even in the trail itself. The very strenuous Permian Reef Trail is the best trail to see fossils in the park, but it is a long challenging hike with a lot of elevation change.
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Hawai’i Volcanoes National Park, Hawai’i
Similar to Craters of the Moon National Monument & Preserve, Hawai’i Volcanoes National Park has examples of tree molds in lava that visitors may see. Lava tree molds are found next to a roadside pullout on the Mauna Loa Road near Highway 11 in the park.
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NPS—Volcanoes and Fossils
John Day Fossil Beds National Monument, Oregon
NPS photo by Tim Gohrke.
The John Day Basin in Oregon is famous for its fossils of vertebrates and plants. It is also notable for its unusually long and complete fossil record, beginning in the Early Eocene and ending in the Late Miocene, spanning more than 40 million years. John Day Fossil Beds National Monument preserves some of the basin’s significant fossil localities. Besides the excellent museum in the Thomas Condon Visitor Center in the Sheep Rock Unit, the best place to see fossils in John Day Fossil Beds is Trail of Fossils in the Clarno Unit. Eocene leaf imprints and pieces of fossil wood are in boulders along the trail. The trail is 0.25 mi (0.4 km) long.
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Petrified Forest National Park, Arizona
NPS photo by Andrew V Kearns.
Petrified Forest National Park is notable for preserving approximately 25 million years of geologic history, recording a wealth of information about a Late Triassic landscape. Hundreds of fossil species of plants, invertebrates, and vertebrates, many of which have not been found anywhere else, have been described from the park. It is most famous for the fossil wood that gave it its name, and is one of the best places in the world to see petrified wood. The silicified fossil logs are also especially known for their beautiful arrays of colors.
The areas in the park with great concentration of petrified wood are locations where log jams formed in ancient river channels. The logs were buried and fossilized through permineralization and replacement by silica. Today the logs are perched on top of the Earth’s surface in the park because the silica they are made of is more resistant to erosion than the mudstones and siltstones of the surrounding Chinle Formation. Several areas with short hiking trails in the southern part of the park have great concentrations of petrified logs, including the Crystal Forest (0.75-mile loop trail), Giant Logs (0.6-mile loop), Long Logs (1.6-mile loop), and Blue Mesa (1-mile loop).
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Puʻuhonua o Hōnaunau National Historical Park, Hawai’i
NPS photo by Justin Tweet.
Puʻuhonua o Hōnaunau National Historical Park is one of five parks that have fossil tree molds in young basaltic lava flows. Like at Craters of the Moon National Monument & Preserve, the tree molds formed when lava flows surround trees during a volcanic eruption. Here, the tree molds are of the endemic Loulu palms and are approximately 1,000 years old. This may seem young to be considered a fossil, but the molds meet the definition of a fossil as they are certainly in a geological context, and provide evidence of past life. Stop 5 on the Historic Walking Tour features a tree mold.
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Link to Volcanoes and Fossils
Theodore Roosevelt National Park, North Dakota
Theodore Roosevelt National Park has in its Paleocene badlands the one of the highest concentration of petrified wood in the United States. The Petrified Forest Trail in the South Unit can be accessed from gravel roads near the western boundary of the park. The trail leads to two areas of petrified wood in the park, both about 1.5 miles from the trailhead. Much of the fossil wood in these locations consists of petrified stumps of sequoia, bald cypress, and magnolia that were rapidly buried by sediments that washed into the area about 60 million years ago.
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Waco Mammoth National Monument, Texas
Waco Mammoth National Monument is a relatively small site, but it has fossils of a possible mammoth nursery herd of about 20 mammoths, as well as of a few other Pleistocene animals. A dig shelter building has been built over the quarry and it features both excavated fossils of Columbian mammoths as well as exhibits, murals, and a small fossil prep lab. A suspended walkway that allows visitors an overhead view of the remains of six Columbian mammoths and a western camel.
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Walnut Canyon National Monument, Arizona
NPS photo by Diana Boudreau.
Walnut Canyon National Monument was established to protect 700-year-old cliff dwellings that are perched underneath rock ledges along the walls of Walnut Canyon. The upper cliffs of the canyon are made of the Kaibab Formation, which was deposited in an ancient sea during the Permian about 270 million years ago. The Kaibab Formation is the same rock layer that holds up the rim of Grand Canyon (see more about Grand Canyon National Park above).The one-mile Island Trail provides access to 25 cliff dwellings and passes through the Kaibab Formation. Fossils of marine invertebrates such as brachiopods, bivalves, and gastropods are present in some of the rock outcrops along the trail.
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Link to Invertebrate Fossils
Wind Cave National Park, South Dakota
The cave system of Wind Cave National Park is in the fossiliferous Mississippian-age marine Madison Limestone. Brachiopods and rugose corals, both marine invertebrates, are visible embedded in cave surfaces along the routes of several Wind Cave tour routes.
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Yellowstone National Park, Wyoming
Yellowstone National Park contains of the largest occurrences of petrified wood in the world, although this part of the park’s geologic story is not as famous compared to its geothermal and volcanic features and wildlife. Coincidentally, though, the park’s most visible fossils owe their preservation to volcanic activity.
During the Eocene, about 49 million years ago, volcanic mudflows called lahars buried forests of sequoias, firs, and numerous deciduous trees almost in their entirety, and sometimes transported entire stumps from where the trees had been growing and deposited them upright where they were later fossilized.
Petrified Tree, a large upright petrified stump of a giant redwood tree, is the easiest fossil to see in Yellowstone National Park. It is located a short pull-off from the Grand Loop Road in the northern part of the park. Specimen Ridge is another place to see petrified wood in the park, but it requires a strenuous hike on a unmaintained and unmarked route.
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Last updated: October 11, 2024