Learn about the geology of Canyonlands National Park.
Located just outside of Moab, Utah where the Moab office of the USGS Southwest Biological Science Center is located, Canyonlands National Park is a sedimentary rock wonderland, a fabulous place to view thick sections of Mesozoic rocks, many of which are not covered by vegetation. Covering over 300,000 acres of the Colorado Plateau, Canyonlands contains four main distinct districts: Island in the Sky, The Needles, and The Maze, and the Green & Colorado rivers. Each district has its own unique characteristics. In 1869, John Wesley Powell’s epic river expedition created some of the earliest maps and geologic observations of this region, including pinpointing the confluence of the Green and Colorado rivers. The USGS commemorated the 150th anniversary of this expedition in 2019.
Throughout the park, millions of years of geologic history are visible at every turn. Sediments such as sand and mud were originally deposited near sea level by ancient seas, lakes, marshes, salt flats, and sand dunes. As these sediments piled up over time, they lithified (turned to rock through compaction and cementation) into a layer cake of sedimentary rocks, each layer recording the buried record of time and life on Earth. Not all the sedimentary rock types are the same. If they were, the landscape would be significantly less dramatic. Instead, stronger sandstone forms steep cliffs and ledges, softer shale forms slopes, and the landscapes have been shaped over time into the interesting landforms we see today.
About 20 million years ago, that began to change as the entire region of the Colorado Plateau was uplifted, or pushed upward, by tectonic activity. During this uplift, magma, or molten rock, also moved into the sedimentary rocks along cracks, hardening into the igneous rocks of the nearby La Sal, Abajo, and Henry Mountains. Today, these mountain ranges tower above the softer sedimentary rocks in the valleys below.
As the Colorado Plateau continued to rise, rivers continued to carve deeply into the rock, revealing layer upon layer of ancient sediments deposited millions of years earlier, incising existing river meanders and exposing a treasure trove of Earth’s geologic history. Water, ice, and wind continue to shape the park today. This desert region averages over 5000 feet above sea level, where snow and ice are present during the winter months. Ice freezing within cracks widens the cracks even more, known as frost-wedging. Infrequent, yet heavy rains surge down the mountains, carrying sediment within its load. All of these processes are ongoing, meaning that the stunning formations we see today will eventually be worn away by erosion. Wind erosion in this area is a topic of current USGS research, as is water.
Island in the Sky District
Island in the Sky is a 2,000 foot-high mesa overlooking the Green River to the west and the Colorado River to the east. Layers of sedimentary rock are visible down the steep walls of canyons cut from the top of the mesa to the rivers far below, exposing roughly 150 million years of geologic history.
From river level, the Honaker Trail limestone can be spotted, while harder sandstone forms “benches” on top of the cliffs. Monument Basin is another spot within Island in the Sky where hard rock left behind has become an unusual formation. Here, harder rock shelters weaker rock underneath, creating beautiful tower formations. A strip of land called “the neck” serves as a physical barrier between Island in the Sky and the neighboring land of the Colorado Plateau. This site is a popular hiking trail where hikers can spot the ancient sand dune deposits of the Navajo sandstone. Upheaval Dome is another interesting feature of the Island in the Sky district. Here, a circular dome of rock rises skyward, caused either by the movement of underground layers of salt or from a meteorite impact and resulting erosion.
The dark red rocks of the Moenkopi Formation were deposited during the Triassic period. The erosion of sandstone and siltstone has exposed fantastic formations, including Balanced Rock, which is visible from the White Rim Road. The unit of rock above the Moenkopi Formation is called the Chinle Formation. This multi-colored unit of fine-grained sedimentary rock is less resistant to erosion than the overlying sandstones and forms more gradual slopes, some of which also contain volcanic ash and bentonite clays.
The Needles District
The Needles District is the Southeastern corner of Canyonlands and was named for the needle-like spires of Cedar Mesa sandstone which dominate the landscape.
The tall, thin spires found throughout The Needles District formed over time from the erosional power of water.
Over 200 million years ago, a shallow sea stretched from here to California, and the area now covered by sandstone spires was part of a vast field of dunes near the edges of the sea. Occasional flooding from mountains in what is now Colorado caused periodic influxes of red sediment, which formed the colorful layers of sediment now visible in The Needles.
About 20 million years ago, the Colorado Plateau began its upward movement due to tectonic uplift. As the region rose, sediment stopped being deposited here, and instead began to be eroded away, carved by the rivers and sculpted by water and the freeze-thaw cycles of ice. Several forces of erosion began to cause surface fractures in The Needles District. At this time, water attacked the cement holding together grains of sandstone, while fractures and cracks accelerated erosive processes.
The Maze District
The Maze District is the least accessible within Canyonlands National Park, with many undeveloped roads and fewer trails in and out of the park than the other districts. Overall, this portion of the park is characterized by deep, labyrinth-like canyons and standing rocks reaching skyward above. If visiting this remote district, be sure to bring paper maps and adequate supplies with you!