Sunday, June 30, 2013

Compton Peak

Columnar jointing on Compton Peak
2.4 miles round trip, 830 feet elevation gain
Difficulty: Easy
Access: Trailhead off Skyline Drive (paved road), Shenandoah National Park entrance fee required

Compton Peak is an easy and noteworthy hike in the North District of Shenandoah National Park. I enjoyed this hike very much: not only does it lead to a good view, but it also leads to one of the most spectacular geological features of the park, a set of columnar basalt in the Catoctin Formation. The hike’s outstanding features, its relative easiness, and its proximity to the Front Royal entrance of the park make it a hike that all Washington DC area residents should do.

I did this hike on a November afternoon, on my way driving from Charlottesville to Baltimore. From Charlottesville, I took US 29 north to Madison, then took 29 business through Madison itself; at the far end of town, I turned left onto Route 231 north. I took Route 231 north all the way to its terminus at US 522; here I turned left and took US 522 into Sperryville and a junction with US 211. At the junction with US 211, I turned left and took that road up to the Thornton Gap Entrance of Shenandoah, where I took Skyline Drive north to Compton Gap at mile 10. Hikers coming from DC can take I-66 west to Front Royal, follow signs for Skyline Drive and then follow Skyline Drive to mile 10.

During my drive in, I stopped at Indian Run Overlook, which was at mile 11, just before Compton Gap. Although the view here was good, the more exciting feature was the huge icicles that hung off the cliff behind the overlook.

Starting from the Compton Gap parking area, I crossed Skyline Drive and started taking the Appalachian Trail south. The trail began a fairly gentle climb up Compton Peak. Along the way, the trail passed multiple large boulders. It was immediately obvious that columnar basalt was quite common all over this mountain: many of the boulders here already exhibited the distinctive hexagonal shapes.

Boulder exhibiting columnar jointing on the trail
After climbing for about seven-tenths of a mile, the trail leveled out on the top of the summit plateau. About 0.8 miles from the trailhead, I came to an intersection at the top of Compton Peak. Two trails led left and right, and the AT continued southward. Here, I turned right and followed the west spur trail. This trail stayed fairly flat, following a rocky trail along the summit for a fifth of a mile. I reached a large rock outcrop at the end of the trail. The outcrop looked to the north, with a good view of the gradually shrinking crest of the Blue Ridge outside the park and of Dickey Ridge. To the northwest, I could also see Shenandoah Valley and Signal Knob. The view to the east was similar to that at Indian Run Overlook.

View northwest from Compton Peak
I took some photos and ate my lunch quickly here before leaving- it was quite windy. I returned to the summit junction and this time took the eastward trail. This trail was also about a fifth of a mile long. I followed the spur downhill, dropping quite a bit down the east side of Compton Peak, including a section with icy rock steps, before reaching a large rock outcrop. A blue blaze led straight onto the outcrop, so I followed the blaze and scrambled up the rock; unfortunately, there wasn’t much of a view from the rock. Mt. Marshall and the Peak were visible but were largely blocked by trees. Only a small window of the Piedmont was visible. However, once I came off the rock, I followed the last section of trail downhill to the left of the rock. The trail ended after circling to the eastern base of the outcrop.

View east from top of boulder
What had been a rock with a disappointing view from above was a geological wonder from below. The rock outcrop was a massive chunk of columnar basalt. The rock was arranged into vertical hexagonal columns. The columnar basalt was quite extensive here: the neighboring few outcrops featured a similar structure. This columnar basalt is part of the Catoctin Formation, which in most parts of the park is composed of a metamorphosed basalt. Here, the basalt seemed a little more intact in its original shape. The basalts of the Catoctin Formation were once huge flood basalts around 700 million years ago. Rifting or other sorts of extensional tectonics caused huge lava flows that flooded the existing landscape. When the exposed lava cooled quickly, it shrank, causing hexagonal joints to form in the nascent basalt. Thus, once the rock cooled and formed, it formed in columns rather in a single block.

This is awesome.
Although the Catoctin Formation is present throughout the park, this is the only place that I know of in Shenandoah National Park that has such an impressive formation of columnar basalt. Columnar basalt can also be found in Upper Whiteoak Canyon.

From here, I retraced my steps to the trailhead.

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