Old Rag Mountain Hikes

Each fall semester, the Department sponsors a day-long hike to the summit of Old Rag Mountain, which is located within Shenandoah National Park. The hike is usually scheduled in October so the weather is crisp and the fall colors are often at their peak. Old Rag Mountain is an eroded granite batholith that first formed during the Grenville Orogeny (1.10 billion years ago!). The granite is coarse grained and contains an unusual blue quartz.

Along the trail we encounter a split in the granite formed by the intrusion of a diabase dike. The stair-step appearance of the diabase was formed by sets of columnar cooling joints that are now eroded. A large boulder has become wedged in the split of the granite so climbers have to squeeze beneath the stone as they ascend!

The summit of the mountain is at approximately 3300 feet in elevation. The trail climbs through 2000 feet of vertical relief.

At the top of Old Rag Mountain these distinctive residual weathered boulders (below) can be seen. These boulders well illlustrate the concept of spheroidal weathering which students learn about in their introduction to geology class.