Speeding Along the Dinosaur Freeway

This EarthCache will take you to the Dinosaur Ridge Dinosaur Tracksite. This area is Jefferson County Open Space and is open to the public. Parking is at the bottom of the hill on either the east or west sides of Dinosaur Ridge, or at the Dinosaur Ridge Visitor’s Center on Alameda Parkway. Access is by walking up the hill, non-motorized bicycles, or by taking the tour bus from the Visitor’s Center. Please DO NOT drive up to the site, as the road has been closed off and only authorized vehicles are allowed to use the road. Also please remember that it is against State Law to collect rocks or remove any fossils from Dinosaur Ridge. Although you will be able to get close to, and measure, the tracks, it is very important that you do not go any higher on the track-bearing strata than the area that is marked off by the yellow nylon cord. This is to ensure that the majority of the tracksite remains undisturbed, yet visible to future visitors.

The Dinosaur Ridge Tracksite packs many dinosaur tracks into a relatively small area. The exposed tracksite is approximately 30 meters x 20 meters, but contains at least 335 tracks from at least 37 individual dinosaurs. The rocks containing the tracks at this site are from the Dakota Group, and were laid down approximately 100 million years ago during the Cretaceous Period.

The rock layers in this formation aid in understanding the local conditions from when the tracks were made. Research indicates that this area was near the edge of the Western Interior Seaway, which was a shallow inland sea that extended from the Gulf of Mexico to the Arctic Ocean. Mud and sand covered the bottom of the inland sea, and this was a perfect medium in which to make tracks of passing dinosaurs. Many tracks are found in the layers at the top of the Dakota Group, and these layers can be traced from Boulder Colorado, southwards into New Mexico. It is currently hypothesized that the coastline of the Interior Seaway may have acted as a migration route, giving rise to the term, “Dinosaur Freeway”.

Lockley et al. (2000) states, “Tracks are the evidence of living animals and provide biological insights into the trackmaker’s anatomy and behavior.” Tracks can tell how large an animal was, how many feet it walked on (two or four), and how many toes it had. Along with the age of the rock, this can help to identify the type of animal that made the tracks. Additional information gained from tracks at the Dinosaur Ridge Tracksite includes social behavior (Iguanodon-like dinosaurs at this site can be seen to have moved in groups) and the speed at which the dinosaurs moved when making the tracks.

N 39 40.865 W 105 11.540 Dinosaur Trackway

The given coordinates will take you inside the fenced area to the public access portion of the dinosaur trackway. It should be stressed that even though GPS receiver signal variations may place the coordinates further into the trackway, you MUST stay in the cordoned area at the northeast portion of the trackway.

The aim of this EarthCache will be to calculate the approximate speed that a dinosaur was moving when it made a particular set of tracks. To complete this task, you will need to: 1.) Determine which species of dinosaur made the set of tracks you are measuring (Iguanodontid or Ornithomimus); 2.) Measure track length and stride length; and, 3.) Plug the lengths into a formula which will give you an approximate value for speed.

The first thing to do will be to determine the type of dinosaur that made a particular track. Four types of tracks have been identified in the Dakota Group strata: Ornithopod and Theropod dinosaurs, crocodiles, and birds. Of these, two types of identified tracks have been made in the area which the general public can access: Thick, broad 3-toed tracks made by an Iguanodon-like Ornithopod dinosaur, and the smaller narrow 3-toed tracks made by a Theropod such as Ornithomimus. The Iguanodontid tracks head south-westerly, whereas the Ornithomimus tracks head southerly at this location.

To calculate the speed of a dinosaur using a trackway, measure the footprint length (straight line distance between the tip of the longest toe to the back of the foot) and stride length (distance between two successive placements of the same foot measuring between equal points). Multiply the footprint length by four to get an estimate of the hip height. Use these measurements in the following formula:

v=0.25 (g^0.5) x (sl^1.67) x (h^-1.17)

Where v=velocity or speed, g=the acceleration due to gravity (9.8 m/sec^2), sl=stride length, and h=estimated hip height (or 4 times the footprint length). It is important that your measurements are in meters taken to at least 2 decimal places.

Your answer to this formula will be in meters/second. Your final mathematical problem will be to change your answer to miles/hour. Since it is easy to find published estimates of dinosaur speed, you will need to show me your work in the email that you send.

So, to log this EarthCache here are the things you will need to send me in an email: 1.) The type of dinosaur track (Iguanodon-like or Ornithomimus) from which you made your measurements; 2.) The footprint length and stride length; and 3.) Your final speed in meters/second and miles/hour. Remember that you must include all work in your email!

Please consider posting photos of yourself, or the local geology, when you log this EarthCache. Photos can be an additional rewarding part of your journey, but posting them is not a requirement for logging this EarthCache, and is strictly optional.

The above information was compiled from the following sources:

2001. Lockley, M. A Field Guide to Dinosaur Ridge. Third Revised Ed.

2001. Lockley et. al. A Brief History of Paleontological Research and Public Education on Dinosaur Ridge. The Mountain Geologist, Vol. 38, No. 3. p. 87-95.

2006. Alexander, R.M. Dinosaur Biomechanics. Proceedings of the Royal Society: Biological Sciences. Vol. 273. Online at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1634776

2007. American Museum of Natural History. Activity: Relative Speed of Dinosaurs. Online at: http://www.ed.mtu.edu/pd/documents/McGinnis_DinosaurFootprintActivity.pdf

2000. Lockley, M.G. et. al. A Guide to the Purgatoire Dinosaur Trackway, Excerpts from the Book Dinosaur Lake, Special Publication 40, Colorado Geological Survey, 1997; in Field Trip Guidebook A Dash with the Dinosaurs: A Mountain Bike Trek to the Purgatoire River Dinosaur Trackway and the Cretaceous-Tertiary Boundary Impact Layer of Southeastern Colorado, La Junta and Trinidad, Colorado.

University of California, Berkeley. Inferring the Possible Speeds of Dinosaurs. Online at: http://www.ucmp.berkeley.edu/diapsids/buzz/locomotion.html

This EarthCache was placed by following the Jefferson County Open Space Rules and Regulations, found online at: http://www.co.jefferson.co.us/jeffco/openspace_uploads/07_rules_regs_english.pdf, and the Geocache Guidelines, found at: http://www.co.jefferson.co.us/openspace/openspace_T56_R120.htm.

Thanks to the Jefferson County Open Space and the Friends of Dinosaur Ridge for allowing placement of this EarthCache! More information on Dinosaur Ridge can be found at the Dinosaur Ridge Visitors Center, 16831 West Alameda Parkway in Morrison, or on the Friends of Dinosaur Ridge website at: www.dinoridge.org