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.
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.
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.
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.
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.
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.
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.
90 million years ago
15 million years ago
By this time, many recognizable features of North America’s modern landscape had begun to emerge.
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.
All images © 2014 Colorado Plateau Geosystems Inc