In the wildest part of the Eagle River valley, there's a hike that ends in a science lesson both simple and beautiful.
There, where the mountains meet the headwaters of the South Fork of Eagle River, two sister lakes sit separated by a lichen-covered moraine.
Eagle Lake and its next door neighbor Symphony Lake look strikingly different: One is a milky, opaque turquoise. The other is a deep, clear green-blue.
Clear Symphony Lake is fed by snowmelt from the nearby Chugach Mountains, as well as precipitation.
Cloudy Eagle Lake is fed by glacial runoff.
So what makes it, and other glacially-fed lakes, that otherworldly color somewhere between milky tea and a robin’s egg?
According to the National Park Service, fine particles of silt deposited by the melting glacial ice absorb all but blue wavelengths – creating an electrically-colored, saturated blue appearance. Meanwhile, the “glacial flour” of fine silt and clay particles combines to give the water an opaque appearance.
The trail that leads to the lakes is an Anchorage-area favorite for hikers, backpackers and even runners.
It begins at the Eagle River South Fork trailhead, which has ample parking but still gets full on sunny summer days. After ascending through a thick forest of spruce and birch, the trail emerges higher on the wall of the valley. Follow this trail for about two miles, past excellent seasonal berry picking spots (the exact whereabouts of the best patches are a guarded secret, but come August you’ll see pickers dotting the hillsides) and then descend to a bridge over the rushing South Fork of Eagle River. Follow the trail through a mostly treeless alpine landscape, past a turnoff trail to nearby Hanging Valley. Finally, you’ll come upon an impressively large moraine, a sign that you are nearly at the lakes.
A moraine is an accumulation of rocks or dirt deposited by a glacier. Pass a small outlet lake that gives the first hint of the striking blue of the main lake, but don’t confuse it for the real thing: To see the lakes themselves, you’ll need to tighten your shoelaces and prepare your dog for about a mile of boulder scrambling over the moraine. At some points you’ll be able to find dirt trails, but for others you’ll be travelling on rock alone. Stop to notice (and avoid crushing) hardy-yet-delicate alpine wildflowers that hug the ground.
Soon you’ll pass U.S.G.S. survey markers and come to what is allegedly an unfinished, circular cabin. From there you can see clearly down to Eagle Lake below, to the left if you’re looking at the mountains. And what mountains they are! Behind the lakes you’ll see the fantastically named Hurdygurdy Mountain, along with other huge peaks like Calliope, Organ, Cantana, Polar Bear and Eagle Peak itself. To the right is the clearer Symphony Lake – a popular fishing spot.