Timpanogos itself is composed entirely of limestone. This is precipitated calcium carbonate and shells of small creatures deposited in a deepening ocean basin during the Pennsylvanian Period, around 320 million years ago. The deposits are several thousand feet thick. As the crust of the western edge of the continent was lifted up, this region became dry land during the Triassic Period (age of reptiles, 200 million years ago). After remaining near sea level during the age of the dinosaurs, Utah was elevated to its present height during the Tertiary Period, beginning around 65 million years ago. As the Great Basin slid downward relative to the mountains of eastern Utah, the limestone was exposed along the Wasatch Fault in Utah County.

As you near the Timpooneke Road, you'll come to a trail fork at N 40° 26.186 W 111° 39.680. There's a fork on the right (Trail 179) that heads downhill to the West Fork of Bear Canyon. About 20 feet later, the trail splits. If you go straight, it dumps you directly onto Timpooneke Road. To follow the GWT singletrack, fork left (south). The trail will parallel the Timpooneke Road, traversing a couple of primitive camp areas that connect to the road, before crossing the road. If you took one of several doubletrack connectors out to Timpooneke Road, you may need to turn and peddle south (left) a little ways along the road. Look for the descent into Rock Canyon at GPS N 40° 26.061' W 111° 39.937' on your right. (Watch carefully! It's very easy to miss it.) Don't worry, it's not as steep coming up the other side.

To add more miles to the ride, when the singletrack hits Timpooneke Road (as above), go straight across through the log fence. Follow the singletrack along the hillside. As it contours along an erosion trench, the Grove Creek trail will join from downhill. Go uphill and cross the meadow. At the doubletrack, turn left. Go a short distance to the doubletrack and turn left again. You're on the Timpooneke Road, heading home.