Haines Junction is a small town of 593 people established back in 1942 during the construction of the Alaska Highway. It’s two hours southwest of Whitehorse and home to Kluane National Park and thundereggs.
I first came across these spherical rocks when I was looking up hikes on YukonHiking.com. The photos and description of these rocks caught my attention and I decided I had to see them for myself. Thunderegg Creek was quickly added to our Yukon hiking list.
These rocks are found in Alsek Valley, right outside the Kluane National Park boundary. When we found out from national park visitor center in town that Alsek River Valley trail is open to bikes, we decided to ride in to see the thundereggs (the two trails are in the same valley). Our plan was to ride to see the rocks, ride back out to the truck, and then head down the Alsek River Valley trail. Since we drove down the road into Alsek Valley some, our ride out and back to see thundereggs was less than 6 miles. Know that there is a creek towards the beginning of the road that may require a high clearance vehicle to ford, depending on how much it’s rained recently.
After some online searches, it turns out that these rocks have been incorrectly named thundereggs. Thundereggs are typically formed within layers of volcanic ash and look like a regular rock on the outside (which these do). But when the round rocks are cut in half, the center is filled with various types of crystals like opal, quartz, jasper or agate. The split thundereggs we came across here didn't have any crystal surprises on the inside. The centers did have a different rock material, but it didn't look like a crystal. Although most times crystals only look like crystals once they've been polished.
According to an article I read online, these thundereggs are really concretions, which is a hard mass that's formed around an accumulation of organic matter. Whatever they geologically are, I was thrilled to see them in person and touch them.
At some point we looked at the ridge above us and noticed that embedded in those cliffs were thundereggs - partially protruding out of the rock face. I guess the rocks eroded over time, causing the thundereggs to fall out of the bluff and down onto the field where we stood.
I was very surprised that there weren't hundreds of thundereggs laying on the ground below the bluff. But it turns out that's because people are/have been taking thundereggs home with them. This leaves fewer and fewer of them at Thunderegg Creek for others to appreciate. "Take only photos, leave only footprints."
Once we made it back to the truck, we turned onto the old mining road that is now the Alsek River Valley trail. The trail contained numerous creek crossings that passed through open grassland surrounded by stands of spruce and poplar.
The views on the trail got better the further we rode in. The wind also got stronger.
It wasn't until we crossed into national park boundary that the wind really picked up, sideswiping us off our bikes. The weather had called for high winds around 25 - 30 mph in the afternoon. I guess for once they were right.
This was the last photo I got of Alsek Valley before we hightailed it back to the truck.
We were in the Haines Junction area from July 25 - August 9, 2016.