Land

Our Story Really Begins...

Today, millions of people are drawn to this magical and mysterious landscape — even though the early Macomb Expedition’s geologist described it as “nothing but bare and barren rocks of rich and varied colors shimmering in the sunlight.” Visitors today are awestruck by the land, at once marveling at the scale, colors, and shapes.

The Colorado Plateau’s iconic, colorful layers of sedimentary rock were deposited by water and wind on top of ancient “basement” rock. For hundreds of millions of years, this region was close to sea level and accumulated the rock strata that we see here today exposed in this arid landscape. The land was periodically inundated with inland seas, lakes, and river systems, which deposited sediments like the Mancos Shale and the Moenkopi Formation. Parts of the region were also intermittently covered with widespread sand dunes like we see in the modern Sahara Desert. The Wingate, Navajo, and Entrada sandstone units preserve these ancient dune landscapes: if you look closely as you hike amongst these units, sets of sloping layers within the rocks called cross-beds trace the ancient surfaces of dunes as the wind slowly built them.

How has the landscape changed?

Evidence of life in these ancient landscapes of Southeast Utah is found in a rich fossil record of marine, freshwater, and terrestrial creatures, primitive fish, plants, insects, and trees. The large number of aquatic fossils — some as old as 500 million years — is no surprise since this region often was covered water. And, yes, dinosaurs also inhabited this area, roaming along the margins of lakes and streams or seeking the water and vegetation of oases amidst the dunes. The first dinosaur fossils in the western United States were discovered by the Macomb Expedition here in southeastern Utah in 1859.

  • Survivor Trilobite

    Tricrepicephalus texanus
    This trilobite survived an injury that broke off one of its spines on the posterior end of its body. Such injuries are not uncommon in Cambrian trilobites, and interestingly, they occur more often on one side of the body than the other – does this mean that the predators attacked preferentially from one side or that the prey trilobites tended to reflexively evade more often to one side? Researchers aren’t yet sure.

  • Willow leaf

    Willow leaf

    Salix cockerel
    Found near Douglas Pass, Garfield County, Colorado.

  • Large trilobite

    Large trilobite

    Hemirhodon amplipyge
    Found near Marjum Pass, Millard County, Utah.

  • Ferns burried in ash

    Ferns burried in ash

    Matonidium sp.
    These ferns grew in a coal swamp and were preserved in white ash after being buried in a volcanic eruption about 100 million years ago. Found near Westwater, Grand County, Utah.

  • Dinosaur tracks

    Dinosaur tracks

    Grallator isp.
    Small carnivorous dinosaurs left tracks on a mudflat between sand dunes when an extensive sand dune desert nearly the size of the modern Sahara desert covered the western United States. Found near Moab, Grand County, Utah.

  • Conifer Stems

    Conifer Stems

    Elatides longifolia
    These stems are from relatives of araucarian or Cypress trees that lived on a coastal delta. Found near Roan Cliffs, Rio Blanco County, Colorado.

  • Utah Crocodile

    Utah Crocodile

    Crocodyliformes indet.
    This armor bone was embedded in the skin of an ancient crocodile that lived in a warm, swamp-like climate. Found in the Book Cliffs, Grand County, Utah.

  • Sago palm

    Ancient sago palm

    Cycalades
    This fossilized trunk of a Cycad is from the late Jurassic period, approximately 150 million years ago. Cycads are seed plants that appeared prior to dinosaurs and are still found in warm-climate areas today. Found in Wayne County, Utah.

  • Predatory worm

    Predatory worm

    Selkirkia sp.
    This worm is a rarity because the shallow seas that covered Utah seldom preserved animals without hard parts; it lived in sediment to ambush its prey. Found in the Drum Mountains, Millard County, Utah.

  • Petrified conifer wood

    Petrified conifer wood

    Coniferophyta
    Approximately 180 million years ago, southeastern Utah was a sand dune desert dotted with oases that preserved life. Fossils include mammal (or protomammal) burrows, large conifer trees, and tracks of large and small dinosaurs. Found along Highway 313, Grand County, Utah.

  • Paradox salt block

    Paradox salt block

    Most of southeastern Utah’s remarkable scenery is due to the simple mineral—salt—which was deposited in shallow seas. Salt domes and erosion created the fins, arches, valleys, and canyons that dominate our landscape. The Moab, Spanish, Salt, Castle, Lisbon, Sinbad, and Paradox Valleys all resulted from the collapse of salt domes. Found near Cane Creek Mine, San Juan County, Utah.

  • Metoposaur vertebrae

    Metoposaur vertebrae

    Metoposauridae
    Metoposaurs were large carnivorous amphibians common in the lakes and rivers that were scattered on the flood plains in southeastern Utah 200 million years ago. Found in Red Canyon, San Juan County, Utah.

  • Precambrian metamorphic rock

    Precambrian metamorphic rock

    Ancient Rock
    This metamorphic rock is one of the oldest in southeastern Utah—approximately 1.7 billion years old. Found in Westwater Canyon, Grand County, Utah.

  • Mancos shale shark teeth

    Mancos shale shark teeth

    Scapanorhynchus & Squalicorax
    Sharks were relatively common in the sea that covered this area about 80 million years ago, and their teeth sometimes were preserved in sandy deposits around the Green River and Cisco deserts. Found near Radio Tower Ridge, Grand County, Utah.

  • Late triassic forests

    Late triassic forests

    Petrified wood
    This specimen likely represents an araucarian conifer. Found near Corral Canyon, Grand County, Utah.

  • Moab coral reef

    Moab coral reef

    Caninia sp.
    Horn corals lived when much of southeast Utah was covered by a shallow tropical sea. Found near Moab Fault Road Cut just north of Moab near Arches National Park, Grand County, Utah.

  • Compressed vegetation (coal)

    Compressed vegetation (coal)

    The carbon of leaves and other plant parts was compressed over millions of years, creating coal in ancient swamps during a warm, semi-tropical climate. Found in the Book Cliffs, Grand County, Utah.

  • Clam

    Clam

    Septimyalina sp
    Bivalve molluscs lived alongside brachiopods and snails in shallow seas approximately 300 million years ago. Found near Fossil Point, San Juan County, Utah.

  • Brachiopod

    Brachiopod

    Neospirifer sp.
    Bottom-dwelling brachiopods are among the most abundant fossils in Pennsylvanian-Permian rocks. These are among the first hard-shelled creatures to appear more than 500 million years ago – and yet they still live in the oceans today. Found near Fossil Point, San Juan County, Utah.

  • Big marine snail

    Big marine snail

    Babylonites sp.
    These relatively large marine snails lived approximately 300 million years ago in the region’s shallow seas. Found near Fossil Point, San Juan County, Utah.

  • Big fish

    Big fish

    Semionotidae
    The dorsal, tail fins, and body of this semionotid fish were covered in thick scales, and lived 190 million years ago in lakes and rivers. Found near Sand Flats Road, Grand County, Utah.

The dramatic topography we see today is due to gradual uplift of the Colorado Plateau and the erosion the area experiences from wind and water. Rivers and flash floods, over millions of years, cut canyons. Fins, arches, and towers form from vertical cracks that allow flakes of rock to spall off, a process that is often hastened by freeze-thaw cycles. Wind also erodes this landscape. A salt layer present under the Moab area behaves somewhat like putty under pressure, and causes fracturing, slumping, and faulting in the overlying rock, making this area particularly rich in exciting fins, canyons, and arches.

Gastonia

IMG_3286

In the Early Cretaceous period, roughly 125 million years ago, the Moab area was home to a diverse array of dinosaurs. Paleontologists have made many exciting discoveries here in Grand County, particularly in a fossil-rich layer called the Cedar Mountain Formation. Portions of this formation, which is exposed north of Moab near Arches National Park, contain some of the richest and most diverse dinosaur fauna from this time period including the large therapod Utahraptor and this smaller herbivore called Gastonia. This model from the Museum’s collection may be seen on display at Moab Giants Dinosaur Park.

Mesozoic Moab

These paleogeographic maps show how the earth’s geology has changed constantly over time; how continents migrate, mountain ranges thrust up and erode, and sea levels rise and fall. At various times over millions of years this southeastern Utah landscape was the bottom of a flooded continental shelf, a flat floodplain crossed by rivers and dotted with ponds, lakes and wetlands — or covered by swamps and forests. The marine organisms living in those warm shallow waters are now the region’s most striking fossils, tracks, burrows and fossilized wood. These maps remind us that our environment is constantly changing even when we’re not aware of it.

Globe 240 MA

240 million years ago

The earth is constantly changing: continents move, collide, and break apart over millions of years. When the supercontinent Pangea began to rift apart, modern day Moab sat much closer to the equator.

Globe 240 MA
Globe 240 MA

170 million years ago

While large parts of the Colorado Plateau were once covered by water, other areas were simultaneously covered in vast expanses of sand dunes. Dinosaurs living in the region during these times would have visited oases to drink and find food, leaving footprints in the wet sand.

170 million years ago
Globe 240 MA

105 million years ago

At this time in the Cretaceous Period, much of western North America was inundated with a large seaway. Portions of the Colorado Plateau were repeatedly underwater during Earth’s long geologic history, as we see from the sediments and aquatic fossils preserved throughout the region.

Creteceous Globe
Globe 240 MA

100 million years ago

One hundred million years ago, this part of the Colorado Plateau contained rivers and floodplains, draining to the east. The rocks of the region preserve a wide array of river environments, lake sediments, floodplains and more.

100 million years ago
Globe 240 MA

90 million years ago

90 million years ago
Globe 240 MA

15 million years ago

By this time, many recognizable features of North America’s modern landscape had begun to emerge.

15 million years ago
Globe 240 MA

Present

Moab today sits at approximately 4,500’ feet above sea level due to relative uplift over time. The rocks exposed at the surface today tell us stories of the region’s dynamic past.

Present

All images © 2014 Colorado Plateau Geosystems Inc