Geologic History

Today, Utah is a land of great geologic diversity and scenery. Many factors have determined the evolution the state has undergone through time. In a sense, it could be said that Utah has had many different faces.

Through geologic time, what is now Utah has been covered by oceans and inland seas as well as completely dry land. The elevation of the land surface has changed as well, ranging from sea level to over two miles above sea level. There have been periods where the topography has been relatively flat and also periods of mountain building and valley formation.

Utah has not always had the seasonal climate that it has today. There have been wet tropical periods, dry dusty desert environments, and cold times that caused alpine glaciers.

The geographic position of Utah has changed through time as well. Due to plate tectonics, the state has moved from a position on the equator to its present location. In doing so, Utah has rotated nearly 90 degrees from an east-west orientation to its present north-south position.

We don’t know as much about the first 3 billion years of Utah’s geologic history as we know about the 540 million years of the Phanerozoic Eon that followed, but 2.5-billion- to 540-million-year-old rocks are exposed in the Raft River Range, Uinta Mountains, and parts of the Wasatch Range, as well as several other smaller areas of the state. These older rocks give clues to the formation of the continent (including Utah), metamorphism, igneous intrusion, erosion of several miles of sediment, and a variety of environments, including oceans, tidal flats, rivers, streams, lakes, and continental glaciers.

Utah’s Geologic History: A Timeline

Expand the tabs below for more in-depth information on changing climate and environments through Utah’s geologic history.

Cenozoic Era

66 million years ago to the present

Period Epoch Millions of
Years Ago
Description of Events
Quaternary Holocene .01 Current erosional and depositional processes dominate. Basin-and-range extensional faults continue to be active. Volcanic eruptions continue in western Utah, as recently as 660 years ago. Great Salt Lake, a remnant of Lake Bonneville, diminishes and accumulates a vast quantity of salt.
Great Salt Lake information
Pleistocene 2.6 Glaciers blanket the Uinta Mountains, the Wasatch Range, and mountains of the Colorado Plateau. Lake Bonneville, a large fresh-water lake, covers many northern and western Utah valleys. Sand and gravel is deposited along the shoreline. Humans first appear in Utah near the end of this epoch, which ended 11,700 years ago.
Ice Age wildlife and glaciersLake Bonneville
Tertiary Pliocene 5.3 Volcanism continues in southwestern Utah. Basin-and-range extensional faulting and regional uplift continues.
Miocene 23 Igneous intrusions continue to form in the Henry and Abajo Mountains. Igneous activity similar to that in the Oligocene continues until approximately 15 million years ago. Basalt flows and volcanic cones form in southwestern Utah. Basin-and-range extensional faulting in western Utah creates mountain-valley-mountain topography and the Wasatch fault zone. Regional uplift rejuvenates major river systems in the Rocky Mountains and the Colorado Plateau. The carving of the canyonlands begins.
Oligocene 34 The igneous rocks that form the Henry, La Sal, and Abajo Mountains in southern Utah begin to intrude. Igneous activity produces intrusive rocks in northern Utah and volcanos in southwestern Utah. The majority of Utah’s copper is probably associated with an Oligocene-age intrusion in the Bingham mining district, west of Salt Lake City.
Eocene 56 Lake Uinta, part of a larger Green River Lake system in Wyoming and Colorado, forms in northeastern Utah. The lake gradually contracts and is replaced by a river system. In the Uinta Basin thousands of feet of sediment are deposited. Granitic intrusions and volcanic flows occur in northwestern Utah during the late Eocene. Eocene-age reservoir rocks contain sizable amounts of oil and gas.
Paleocene 66 Eroding highlands prevail in western Utah. The Uinta Mountains, smaller uplifts, and the Uinta Basin, become prominent features in eastern Utah. Lake Flagstaff forms in central and northeastern Utah and possibly extends into southwestern Utah. Mammals flourish.

Mesozoic Era

240 to 66 million years ago

Articles on dinosaurs and fossils from the Mesozoic Era
Period Millions of
Years Ago
Description of Events
Cretaceous 145 Lake and river systems gradually decline. Sediments from highlands near the Utah-Nevada border spread eastward. In eastern Utah, seas invade from the east. Western Utah rises due to thrust faulting and folding generated by east-west-directed compressional forces. Dinosaurs and reptiles wander through major coal-forming swamps and marshes near the coastline that gradually retreats from central Utah eastward. Dinosaurs disappear at the end of this period.
Jurassic 201 A large, sandy desert covers most of Utah during the Early Jurassic. The resulting rocks now create some of the most spectacular scenery in Utah’s national parks. Later, shallow seaways from the north invade Utah twice. In central Utah, the Arapien basin develops and receives over 6,000 feet of sediment including large amounts of gypsum and salt. In the Late Jurassic, dinosaurs roam within extensive lake and shifting river systems. Granitic intrusions form in western Utah. Jurassic-age host rocks contain large uranium deposits located in the Colorado Plateau and extensive oil and gas reserves in northern Utah. The first birds evolve.
Triassic 252 Shallow seas from the west spread across northern and western Utah and occasionally overlap with eastern and southern mudflats that are crisscrossed by reptiles and amphibians. After a period of erosion, river and lake systems dominate. Some of these sediments now contain large quantities of petrified wood. Currently uranium is found in Triassic-age rocks of the Colorado Plateau. Dinosaurs and primitive mammals appear.

Paleozoic Era

570 to 240 million years ago

Period Millions of
Years Ago
Description of Events
Permian 299 Deposition continues in the Oquirrh and Paradox basins. Red rocks form in the Paradox basin of sediments shed from the Uncompahgre highland.
Pennsylvanian 323 Seas containing fusulinids, brachiopods, and conodonts cover most of Utah. Sediments continue to accumulate in the Oquirrh basin. The Paradox basin and the adjacent Uncompahgre highland develop in southeastern Utah. Salt, potash, and organic-rich shale accumulate in the shallow, restricted Paradox basin. Pennsylvanian-age reservoir rocks contain large volumes of oil and gas. Reptiles originate during this period.
Mississippian 359 Warm, shallow seas rich with life cover Utah for most of this period. The Oquirrh basin develops in northwestern Utah. Large quantities of limestone are deposited. Mississippian-age reservoir rocks hold an abundant amount of oil and gas.
Devonian 419 Shallow, temporary seas in eastern Utah, and deeper seas in the west contain primitive fish, corals, brachiopods, and conodonts. The Stansbury uplift in north-central Utah develops into a prominent ridge above sea level during the Late Devonian. Amphibians appear.
Silurian 444 Shallow seas containing corals and brachiopods blanket Utah. Dolomite is the predominant rock being formed.
Ordovician 485 New life forms prosper in fluctuating seas of western Utah while eastern Utah remains above sea level. The first vertebrates, primitive armored fish, evolve.
Cambrian 541 Subsidence of western Utah continues. Trilobites thrive in the deep seas of western Utah, while shallow, oscillating seas cover eastern Utah.

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Utah’s Early Cretaceous Fossils Provide Critical Data on the Opening of the Atlantic Ocean Dinosaurs 2018
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The Uinta Mountains: A Tale of Two Geographies Mountains 2014
How can sedimentary rocks tell you about Utah’s history? Geologic History 2014
The Early Miocene Markagunt Megabreccia: Utah’s Largest Catastrophic Landslide Geologic History 2013
Ancient Landslides of the Beaver Dam Mountains, Washington County, Utah Geologic History 2009
Ancient Exhumed River Channels of the Morrison and Cedar Mountain Formations Geologic History 2008
Utah’s oldest fossils are found in the Uinta Mountains Fossils 2005
UGS Publishes The Geology of Millard County, Utah Maps 2004
Inverted Topography in the St. George Area of Washington County Volcanoes 2002
What is a rock formation? Geologic History 2001
Utah’s Sevier Thrust System Geologic History 2000
What is the Grand Staircase? (pdf) Landforms 1999
Utah: A Geologic History Geologic History 1998
Utah's Geologic History Geologic History 1993
The geology of Snow Canyon State Park, Washington County, Utah (pdf) Volcanoes 1992
The geologic story of GK Gilbert Geologic View Park Geologic History

Topic Articles: 31