This summer, quite a few visitors to Yellowstone have walked up to the Grant Village visitor center desk and asked me the same question. “Can you tell me what your favorite hike is? I know you’ve got to have one that you like the best.” The implication is that they would go ahead and hike that particular trail since it is a ranger’s favorite. Well, besides reminding them that my personal choice might not necessarily coincide with their personal choice, I would always respond by saying that all the trails I’d hiked so far are equally my favorites.
|Gallatin Range from Observation Peak|
I can’t even really be certain what it is about Observation Peak that catapulted it to the top of my Favorite Yellowstone Hikes list. There are more than 1,000 miles of trails in Yellowstone, and I’ve hiked maybe 80 or so of them during the course of this summer. All of the trails I’ve traversed are distinctive and absolutely exquisite. And so I’ve got at least 900 more miles of trails to hike before I need to repeat any! But Observation Peak is without doubt a special place. I will definitely go again sooner than later.
Friday–hiking buddy Sasha and I chose to start our trek one mile north of Canyon junction on the Canyon–Tower Road. After a brief foray through a pine forest we soon broke out into open meadows and across small spring creeks for 2.2 miles to Cascade Lake, a small lake situated on the Solfatara Plateau at the base of the Washburn Range.
|Sasha points the way|
|Cascade Lake trail on the Solfatara Plateau|
We would climb 1400 feet in the next three miles and be rewarded with dazzling views of Grebe Lake (headwaters of the Gibbon River, which joins the Firehole River at Madison to become the Madison River), Hayden Valley, and the Central Plateau of the Yellowstone caldera. Entire hillsides, now recovering, were burned in the fires of 1988 that swept through 793,000 acres – about 36% of the park. Every summer fires occur; the hazy sky in these images is caused by the Point fire on the east side of Yellowstone Lake.
|Grebe Lake, the headwaters of Gibbon River|
Of the two main episodes of volcanism in the Yellowstone area, the Washburn Range Volcano in the north–central part of the park came into existence during an older period of volcanic activity that occurred in northwestern Wyoming 55–40 million years ago during the Eocene epoch. During this tectonically active time other volcanic fields were also formed – the Absaroka Range along the eastern side of the park, Bunsen Peak south of Mammoth Hot Springs in the northern part of the park, and intrusive igneous rocks of the southern Gallatin Range in the northwestern corner of the park.
Since Observation Peak is part of the Washburn Range I expected to see similar kinds of rocks that are on Mt. Washburn to the east. I also checked the geologic map. As we gained elevation I ooohed and aaahed at outcrops of angular conglomerate or breccia – coarse, angular fragments of rock in a fine-grained matrix – indicating past mudflows and debris flows from Eocene volcanic activity.
|Breccia outcrop - Sasha for scale|
|Vein of opalized silica|
But at the peak, the rock seemed to change from this breccia; the peak appears to have been mapped as part of the Pleistocene Swan Lake Flow basalt. This basalt flow would have occurred after the third caldera-forming eruption of 640,000 years ago. Since Observation Peak itself is outside of the caldera boundary its rocks would not have been obliterated by the explosion. However, lava flows such as the Swan Lake Flow, which occurred for hundreds of thousands of years after the caldera–forming explosions, could naturally have blanketed these nearby older rocks of the Washburn Range.
I could be mistaken about the Swan Lake Flow being at the top of Observation Peak, however – it is mapped as a tiny speck within the Tertiary volcanics and I could be looking at the wrong contour. The rocks on the peak looked less to me like a basalt than a tuff, but they were definitely not breccia. Unfortunately the trail is not drawn to the peak on the geologic map but follows away from it, around Cascade Lake to Grebe Lake. For me, fine-grained volcanic rocks can be difficult to identify in the field.
|Grebe Lake and the Central Plateau|
We stopped to watch a pair of blue grouse clucking in the undergrowth. On our return trip down past Cascade Lake the two swans were still busily feeding, but in the meadows the bison were nowhere to be seen. The guidebook says that in years past there has been a beaver lodge at the south end of the lake and a lodge and dam on Cascade Creek. When I return next time I will most certainly check them out.
|Fireweed of late summer|
Check it out:
Christiansen, R.L., 2001, The Quaternary and Pliocene Yellowstone Plateau Volcanic Field of Wyoming, Idaho, and Montana, USGS Professional Paper 729-G.
Marschall, M.C. & Marschall, J.S., 2008, Yellowstone Trails: A Hiking Guide, 30th Anniversary Edition, Yellowstone Association.