Just southwest of Mount Shasta and soaring high above the Upper Sacramento River is a dense cluster of exposed granite spires and domes simply known as Castle Crags.
Reminiscent of the towering granite of Yosemite National Park farther to the south, Castle Crags was formed in a fashion and timeline similar to much of the Sierra Nevada Mountains. Much older than the Cascade Volcanic Arc, Castle Crags is an intrusion* that formed roughly 100 million years ago by the subduction of the Farallon Plate as it passed under the North American Plate. Over time the granite intrusions exfoliate large convex slabs, resulting in rounded forms like Castle Crags Dome (or Yosemite's Half Dome).
The trailhead for Castle Crags Dome is very accessible from I-5, but because the trail climbs 2,100 feet in 2.5 miles, the hike should be considered challenging.
Before departing up the Crags Trail, be sure to take in the view of the spires and park from Vista Point on the eastern end of the parking lot. The well-maintained trail up to the Dome travels though a fairly dense forest of ponderosa pine, incense cedar, and Douglas fir before views of the Dome and other outcroppings begin to appear. If you are hiking during the summer months, fill your water bottle at the Indian Spring where crystal clear and clean water flows from the mountain. Once you reach the top the trail disappears into a sea of green manzanita bushes, but numerous paths can be found by scrambling across and around any one of the many granite bodies of rock. Note that scrambling to the top of the Dome is possible without technical gear, but it certainly isn't for those who fear heights and definitely should not be attempted when conditions are wet and the rock is slippery.
*Igneous rock forms in one of two ways: 'extrusion,' such as a volcanic eruption above the earth surface, or 'intrusion,' in which rock solidifies below the earth's surface and is slowly pushed upward.