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Mountain Bikes by Ari and JR

We bike on some of the wildest rock formations in the country. It's all sandstone here in Moab, Utah, but the trails feel different when we're biking. Sometimes it's rolling hills and sometimes it's ledges and dropoffs. No two trails are quite the same; each one challenges us in a different way. We want to know why these trails are so different!

What did we do?
We picked two trails that seemed different, Porcupine Rim and Slickrock. Then we biked a 1-mile stretch of each one. We kept track of how long it took to complete the path, the average speed and our peak bike speed. We also checked the number of jumps, steepness, number of gear changes and basic landscape features. We wrote down anything else we noticed along the way.

What did we find out?
Sandstone comes from pebbles and sand that get "glued together" over time. Sandstone sure seems to vary a lot and the differences affected our biking. Porcupine Rim was crazy. There was a lot of loose gravel and large rocks along the trail. There were also a lot of jumps and broken rock. The sandstone seemed to be made from larger rocks and pebbles, which break easier and clutter up the trail. Slickrock's sandstone only had small sand grains, and a lot of bowl-shaped valleys. It was a smoother ride than Porcupine Rim, with very little debris. We figured the differences come from the way the two areas formed. Porcupine Rim's rock must have been put there by flowing water, maybe a river that dried up. Slickrock looks like a petrified sand dune, which tells us that wind must have brought all the sand here. We're going to bike some more and look for more clues to confirm our theories.

What can you do?
  • Bike down a few different trails in your town. Write down the different features you notice on each trail. Collect small samples of dirt and pebbles from each trail. Did you go faster on one trail? Was one trail more treacherous? How do you think the area was originally formed?
  • Try biking on a dirt, gravel and paved road. On which surface did you ride the fastest? Which road felt like the most work? How does the surface you're riding on affect the way a bike handles?
  • How would you design safer bike tires for certain roads, landscapes or weather conditions? Do you really have to leave your bike in the garage when there's snow on the ground? Design a new snow tire for your bike!
  • Use this earth science investigation as a science fair project idea for your elementary or middle school science fair! Then tell us about it!
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