A lonely old rock

Farm Forum

It probably took thousands of years for gigantic, house-sized boulders come to rest east of what is today Flandreau.

The rock was part of tons of boulders, billions of grains of sand and just plain dirt riding on glacial sleds that plowed their way into what is today eastern South Dakota about 12,000 years ago.

Together, these particles large and small formed what we know today as the Coteau de Prairie, on a sliver of South Dakota, and that huge boulder, sit.

As the glaciers retreated from whence they came, they dropped their heavy cargo of debris, rocks large and small, dirt and grains of sand where the sun and warm weather dictated.

Today, what is the largest of these glacial rocks in South Dakota—called a glacial erratic—can be seen east of Flandreau just off Highway 34.

It is somewhat off the beaten path, but easy to reach.

Head for Pipestone and watch for the sign.

At the sign, turn south for two miles. You’ll see the beautiful, but now closed Lone Rock Church off to your left. Turn on the gravel road leading past the church and continue on for about a mile.

As you drive, you’ll see a small glacial erratic to your left mostly buried in the soil just after passing by the church. But that’s just a preview, not the one you’re looking for. The much bigger one is just ahead. You’ll come to a dead end. Look to your left. There stands the behemoth.

Lone Rock sits in ponderous repose in a cow pasture. It’s over 25 feet high and 40 paces around its base. The erratic has been estimated to weigh about 100 tons, but that’s just the visible part above ground.

Another fifty or seventy-five tons of the pink granite rock might be below ground. For centuries the Lone Rock was a guide for Native Americans and then for pioneers coming to the area. The rock has been a guide-post for centuries and a site for picnics and family outings since the late 1880s.

Crowning the rock is a small boulder that was actually part of the rock until lightening jarred it loose.

It is believed the rock slid down encased in glacial ice from what is today Monitoba, Canada. Its ride was probably on the glacier known as the Wisconsin Drift.

This all happened during the Pleistocene Epoch that started about 1.8 million years ago.

There are three little sisters to this giant rock near the Pipestone Monument in Pipestone, and more relatives in a field one and one half miles south of Highway 324 south of Aurora. Some believe those rocks were part of the cargo that brought the big Lone Rock, the mother of all glacial erratics, to South Dakota, that’s now parked east of the old Lone Rock Church near Flandreau.

Take all the time you need getting out to see it. It isn’t going anywhere soon.

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