After leaving Snowmass, our next stop was Dinosaur National Monument, located right at the Colorado-Utah stateline. Discovered in 1908, the namesake of the National Monument is a dinosaur fossil quarry (an excavation site) where, during the first decades of the last century, thousands of bones have been uncovered and shipped to many museums across the US. To enable an easy acess by visitors, a building has been constructed around the excavation site which contains hundreds of smaller and larger bones, still embedded in sandstone. Paleontologists assume that, some 150 million years ago (in the Jurassic period), hundreds of dead dinosaurs were transported by an ancient river to a shallow spot, where they formed a large pile that was covered by sediment over the next millions of years. Similar to the formation of petrified wood, the ever increasing pressure of the growing sediment layers forced fine sand particles into the bones and created perfect sandstone replicas of the original bone material. Later, the whole area was uplifted and tilted by various mountain building forces. Subsequent erosion washed away most of the upper layers and made the ancient dinosaur graveyard discoverable.
Part of the excavation site with dinosaur bones still embedded in sandstone
The majority of the dinosaurs found here are sauropods, huge plant-eating “long-necks”. The main carnivorous dinosaurs here are allosaurus, similar to the T-Rex of the cretatious period.
An excavated Allosaurus skull
Allosaurus skeleton, made using bones that were found here