Pikes Peak Granite settles in on Canon City’s Geology Time Trail
at the 1.08 billion year mark.
By Cindy Smith
The Crossroads Through Time – Geology Time Trail has three new boulders representing one of the most iconic geologic features in the United States – Pikes Peak, America’s Mountain. These most recent arrivals along the trail are placed at the 1.08 billion year mark, the time period when the Pikes Peak granite was created.
Pikes Peak granite
The Geology Time Trail
The trail is located just west of Cañon City at the Pueblo Community College-Fremont Campus. At a scale of 1 foot = 1 million years, the 2,300 foot trail provides a visual perspective which helps participants grasp the immensity of Deep Time. Twice around the trail represents the life span of Earth at 4.6 billion years.
The Geology Time Trail at PCC-FC. The red X is 1.08 billion years.
Multiple boulders from local geologic formations dot the trail at their representative time periods and will, once funds are available for interpretive signs, help explain the environment at the time of their deposition, fossils and the role of biostratigraphy, the historical and economical importance of local quarrying, and will encourage community recognition and understanding of the surrounding landscape. The three 3,000 pound Pikes Peak granite boulders will help illustrate the story of the formation of America’s mountain for those that walk the Geology Time Trail.
The Geology Behind Pikes Peak Granite
Anyone who has ever had the good fortune to drive to the summit of Pikes Peak or has hiked up Barr Trail or the Manitou Incline knows well the beautiful red crumbly rock that covers the mountain’s slopes. Pikes Peak is composed almost entirely of this granite, made up of feldspar (red), quartz (grey-white), and biotite mica (shiny black), and which weathers into coarse grains of rock fragments.
The slopes of Pikes Peak are covered in this loose marble-sized scree, and many a hiker has learned the hard way to avoid these little ball bearings. To understand the crumbling nature of Pikes Peak granite, we must go back about 1,080,000 years. At that time, an enormous bubble of magma (molten rock that doesn’t reach the surface of the Earth) thrust its way up and into ancient rocks forming the Earth’s crust. That bubble cooled and solidified into a dome called a batholith, and once that dome was exposed, it became Pikes Peak. But the process of hardening and outcropping would take another 1,010,000 years.
The Pikes Peak batholith extended at least 80 miles north/south and 25 miles east/west of Pikes Peak and remained hidden a few miles below the surface of the Earth until 70-35 million years ago, when the Rocky Mountains uplifted, most likely due to plate tectonics as the Farallon Plate subducted under the North American Plate near present-day California. This uplift is called the Laramide Orogeny (orogeny simply means mountain building). It raised Pikes Peak to its current height of 14,115′, an uplift that continues today.
Once the Pikes Peak batholith of granite was exposed, cycles of freezing and thawing weathered the rock, causing it to break apart, but not in small sand-grain sizes. Because the magma making up the batholith that originally created the granite cooled so slowly, it allowed large crystals to form. It is these large crystals of salmon-colored feldspar that easily crumble, breaking down the original granite rock, coating the slopes and teasing the hikers.
Permission and Transport
Crossroads Through Time and the Pueblo Community College – Fremont Campus are extremely pleased to have been granted permission to transport three boulders from historic Pikes Peak to our Geology Time Trail.
We are indebted to the generosity of Oscar Martinez, District Ranger of the Pike National Forest – U.S. Forest Service, for his permission to acquire Pikes Peak granite as an educational resource. We also wish to thank Jack Glavan, Manager of Pikes Peak – America’s Highway, and Kelly Thompson, Pikes Peak Crew Lead, for their coordination of the logistics involved in locating and loading of the boulders. The efforts of these three individuals in support of the Crossroads Through Time – Geology Time Trail project is greatly appreciated.
Rich Jansen, owner of Penrose Truck Sales, and Carl provided professional transport of nearly 9,000 pounds of granite to the Geology Time Trail.