Morrison Formation facts for kids

The Morrison Formation is a special set of rock layers found in the western United States. It's famous because it's the best place in North America to find dinosaur fossils! These rocks were formed during the Jurassic period, about 156 to 147 million years ago.

The Morrison Formation is made up of different kinds of rocks like mudstone, sandstone, siltstone, and limestone. They can be light grey, greenish grey, or even red. Most of the dinosaur fossils are found in the green siltstone and lower sandstone layers. These rocks tell us about the ancient rivers and floodplains that existed during the Jurassic period.

The distinctive banding of the Morrison Formation, a group of rock layers that occur throughout Dinosaur National Monument and the source of fossils like those found at the Dinosaur Quarry.

Typical exposure of the Cedar Mountain Formation overlying the Morrison Formation, south of Green River, Utah.

Where is the Morrison Formation Found?

The Morrison Formation stretches across a huge area, about 1.5 million square kilometers (600,000 square miles)! You can find it in states like Wyoming, Colorado, Montana, Utah, and many others. Even though it covers a vast area, only a small part of it is visible on the surface for geologists and paleontologists to study. Most of it is still buried deep underground.

The first dinosaur fossils in the Morrison Formation were found in 1877 by a person named Arthur Lakes. This discovery led to a big competition between two early paleontologists, Othniel Charles Marsh and Edward Drinker Cope, who were both trying to find the most fossils. This time was known as the "Bone Wars."

Morrison at the type locality (the location that defines the formation) at Dinosaur Ridge, west of Denver, Colorado.

In some areas, like Colorado, New Mexico, and Utah, the Morrison Formation was also an important source of uranium, a special metal used for energy.

What Was the Environment Like?

During the time the Morrison Formation was created, the Earth looked very different. The supercontinent of Laurasia had just started to break apart into North America and Eurasia. North America was moving north and was in a warm, subtropical area.

The land where the Morrison Formation now sits was mostly low-lying. Rivers, lakes, and swampy areas covered the landscape. As the early Rocky Mountains began to rise in the west, they pushed sediment (like sand and mud) down into a large basin. This sediment was carried by rivers and then settled in the lowlands, forming the layers of rock we now call the Morrison Formation.

In the northern parts, near what was then the Sundance Sea, there were many swamps and lots of plants, which is why coal can be found there. But in the southwestern parts, it was much drier, like a desert with sand dunes, showing how varied the environment was.

Dinosaur National Monument

Multicolored beds of the Brushy Basin Member of the Morrison Formation near Carnegie Quarry

Dinosaur National Monument is a special park located on the border of Colorado and Utah. It's famous for its amazing dinosaur fossil beds, often called the Dinosaur Quarry. Here, you can see many dinosaur fossils, including meat-eaters like Allosaurus and huge long-necked dinosaurs called sauropods.

The fossil beds were discovered in 1909 by a paleontologist named Earl Douglass. He and his team dug up thousands of fossils and sent them to the Carnegie Museum in Pittsburgh, Pennsylvania, for study. In 1915, President Woodrow Wilson made the area a National Monument to protect these important discoveries. The monument was later made much larger to include the beautiful river canyons nearby.

What Dinosaurs Lived Here?

The Morrison Formation is like a treasure chest for dinosaur fossils! Many different types of dinosaurs have been found here.

• Meat-eating dinosaurs (Theropods):
  • Allosaurus
  • Torvosaurus
  • Ceratosaurus
  • Coelurus
  • Ornitholestes

• Long-necked dinosaurs (Sauropods): These were some of the biggest animals to ever walk the Earth!
  • Apatosaurus
  • Diplodocus
  • Brachiosaurus
  • Camarasaurus
  • Amphicoelias (possibly the largest dinosaur ever!)

• Plated dinosaurs (Stegosaurs):
  • Stegosaurus
  • Hesperosaurus

• Plant-eating dinosaurs (Ornithopods):
  • Dryosaurus
  • Camptosaurus

These incredible fossils help scientists learn more about what life was like millions of years ago during the Jurassic period.

Images for kids

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  Type locality for the Morrison Formation above the town of Morrison, Colorado.

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  Type locality of the Salt Wash Member near White Wash, Grand County, Utah. The Morrison Formation is underlain by the brick-red Summerville Formation.

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  The Jurassic-Cretaceous boundary is seen where the red and purple beds of the Morrison Formation abruptly contact the drab, gray bed of the overlying Cedar Mountain Formation. The contact is the K1 unconformity. Jessie's Twist, southwest of Green River City, Utah.

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  Brushy Basin Member showing the purple and red colors of paleosols (ancient soils). East side of the San Rafael Swell, Emery County, Utah.

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  Gypsiferous facies of the Ralston Creek Member exposed in a road cut, Fremont County, Colorado.

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  Tidwell Member at the type section, Shadscale Mesa, Emery County, Utah.

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  "Popcorn" texture due to bentonite, formed from volcanic ash, characterizes the Brushy Basin Member

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  Workers inside the Dinosaur Quarry building, at the Dinosaur National Monument.

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  Fruita Paleontological Resource Area. One of the sites is denoted by the arrow.

See also

In Spanish: Formación Morrison para niños