My “Fossil Grandpa” took me to visit this neat site when I was in Texas last summer (2013). We drove to a small rural community, where it seemed there wasn’t anything to find. However, my Grandpa pointed out me to a small trail, full of flowers that Jane (my sister) had stopped to admire, which eventually led down a steep trail into the riverbed. This was definitely not a popular hiking trail and I doubt many people (except geologists) have been to this spot. The site is an ‘Earthcache’, which, in the USA, is a type of geological site that teaches you about a unique geoscience feature. I have been to several Earthcaches in Texas and to at least four in other states (Colorado, Iowa, North Carolina and Florida); and have learned some interesting lessons. Here, our job was to study the dinosaur tracks and answer some questions1.
What type of dinosaur made these tracks? A theropod like Velociraptor or T-rex, or maybe even the recently discovered Lythronax argestes? It must have been some type of carnivorous predator; and to think I was standing right where it walked so long ago. It was a little frightening to imagine one coming along and what that would be like in real life.
The first task was to measure the stride. The stride is the distance between two footprints (right/right), not the step length as shown by Jane and me (right/left). I calculated the stride length as being 284.5cm. Next, I had to measure the length of at least one footprint. In fact, I measured several and took the average to be 46cm long. Then, I calculated the hip height, which equals five times the print length (or 5 x 46cm), which is 230cm. (My hip height measures only 76cm.) Next, I calculated the length of the dinosaur, which is ten times the print length (10 x 46cm), which is 460cm or 4.6m. I am only 132cm inches long (lying down), but I also don’t have a tail like a theropod.
The final task was to determine if the dinosaur was walking, trotting or running. To do this, you must divide the stride length by hip height, which is, in this case, was 284cm/230cm = 1.235. I first guessed that it was walking, because the prints were so clear and there was no smudging. But was I right?
Yes, I guessed correctly! For the calculation stride length divided by hip height the following values correspond to motion: less than 2.0 is walking, 2.0 to 2.9 is trotting and greater than 2.9 is running.
I had a lot of fun at the Earthcache with my Grandpa and enjoyed learning how to interpret dinosaur tracks. As we were exploring some more, he showed me some interesting layers. Some thick, hard white layers turned out to be deep water limestone deposits. The thin bedded, grey layers in between are shallow water mudstones. The dinosaur tracks were found at the base of this lower mudstone layer, meaning that is was walking in shallow water (a lake or river) on a muddy surface.
Reference
- Track Meet? Cache GC1RZM5 by Waterweasel &Tygress.
About the author: Jack Shimon is a member of the Pikes Peak Pebble Pups in Colorado Springs; and is in the Colorado Springs Mineralogical Society Unit. He is in 3rd grade and also enjoys cub scouts, mountain biking and playing the drums. He is always conducting research on earth science topics, either through science or art.
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