Glacial Signatures Written on the Land

Ten thousand years ago, at the end of the last ice age, Vilas County was locked under a solid layer of ice. The glaciers are long gone now, but you can still see evidence of them everywhere you look. I wrote over the summer about how the retreating glaciers formed the kettles that are now our many lakes and bogs – this county has the highest density of natural freshwater lakes of anywhere in the world. The lakes may be the most obvious signature the glaciers left behind, but they’re not the only one.

The photo above was taken standing on top of an esker – you can see that you’re looking along a ridge that drops off on either side.

Eskers are formed by streams of liquid water flowing under and through glaciers. As it flowed, the stream deposited a ribbon of gravel and sediment between the ice walls surrounding it. When the glacier retreated, this is what was left behind. Ours snakes along the margin of one of our kettle bogs.

We also have a lot of till, jumbled collections of rocks and boulders that the glaciers scraped up somewhere else and dumped here. The rocks I flipped for International Rock Flipping Day this year arrived on the property this way.

Was the area where you live ever glaciated? How can you tell?

Further reading: Pleistocene Geology of Vilas County, Wisconsin

Black Canyon of the Gunnison

Arches National Park and Rocky Mountain National Park are both famous, and with good reason, but on our way home we stopped at one more that you may not be so familiar with: Black Canyon of the Gunnison National Park, in southwestern Colorado.

To get there, you drive along a winding road through fairly nondescript hills covered with juniper, pinyon pine, and Gambel oak. Shortly after you pass through the entrance station, though, you arrive at the first overlook and are confronted with this.

A jagged canyon plunges before you. Even though the Gunnison River is so far down that in some places you can barely see it, the roar of the rapids below is always in your ears; the river drops an incredible forty-three feet per mile.

Two facts jumped out at me as we read the brochure and looked at the displays in the visitor center. First, although American Indians and fur traders had certainly known of its existence long before, no written description of this massive canyon was published until the latter half of the nineteenth century. (It’s so rugged that, unlike at the Grand Canyon in Arizona, there’s no evidence that American Indians ever lived within the gorge – the Utes stayed to the rims.) Second, it’s believed to have formed in a fraction of the time it took to form the Grand Canyon, even though the Black Canyon is carved into much harder rock. Apparently some of the oldest exposed rock in the world, over two billion years old, is found here.

This post brings me to the end of my photos from Road Trip 2011. While you’ve been reading about my adventures in Utah and Colorado, I’ve actually been on my way up to northern Wisconsin to begin my master’s degree, stopping to visit some friends along the way. This post is being written and scheduled ahead of time, but by the time you read it I will have been in Land O’ Lakes for a week. Now that I’ve had a chance to settle in, watch this space for my first posts about the North Woods!

More Arches

Turret Arch
Double Arch
Skyline Arch
Landscape Arch

The features that give Arches National Park its name form when enormous fins of sandstone are weakened by alternating freezing and thawing of water that seeps into the porous rock. Once a hole forms, it is enlarged by weathering and rockfalls, and eventually it will collapse completely. There are over 2000 natural arches within the park’s borders.