The Ottawa National Forest includes almost one million acres of lakes, rivers, waterfalls, and forested hills of the Western Upper Peninsula. Stretching from the Peshekee Highlands north of Champion to the Michigan-Wisconsin border, the forest contains the Sturgeon River Gorge, McCormick Tract, and Sylvania Wilderness Area. Among its treasures are some unique geologic features to Michigan - three volcanic plugs.
A volcanic plug is the remains of an ancient volcano. Once a volcano becomes dormant and succumbs to the powers of erosion, only the toughest rocks, the hardened volcanic plug, will remain. The size and condition will depend on the type and age of the volcano, and chances are that it will not be in an ideal chimney shape.
The most popular volcanic plug of the Ottawa National Forest is located very close to the Sturgeon River Gorge. Silver Mountain raises two hundred and fifty feet from the surrounding Baraga Plains, though its proximity to the gorge exaggerates the height. This mountain has several flights of stairs reaching from the parking lot to the peak, making the climb quite easy. The southeastern cliffs are quite steep, but the mountain can be scaled without the stairs from the west. Silver Mountain offers excellent views of Prickett Lake and the Sturgeon River Gorge, and you can even pick out Mount Ripley on clear days.
Silver Mountain is somewhat popular nature stop for tourists and locals alike, but the other two volcanic plugs are relatively unheard of. Mt Kallio is located near Covington and Watton, and while it is on state land, is difficult to reach without crossing several bull pastures. There are a number of old forest highways and four wheeler tracks crisscrossing the woods around the Mt Kallio, and without signs or clear trails, If you can find your way to the mountain, you'll be rewarded with a limited northern view up the Perch River valley. The peak of the mountain does not rise higher than the surrounding rolling plains, and without the wide river valley eroding the land to the west and north, Mt Kallio would probably be underground.
Further to the south is the last volcanic plug, Haystack Mountain. This little mountain is my favorite of the three, as its shape most closely resembles an actual volcanic chamber. A sudden up thrust of rock, about a hundred feet tall and circular in shape, is located in an otherwise normal forest near the East Branch Ontonagon River. This mountain is fairly easy to reach, less than a half mile from a dirt road, and involves little bushwhacking. The climb is difficult, as the rock is uniformly steep on all sides, but the views and flat, pine-covered top are more than worth it.
All three of these mountains are located in the Ottawa National Forest and are accessible for hikers. Silver Mountain is located along Forest Highway 2270, with signs and a nice parking lot for climbers. Mt Kallio can be reached by heading due west or north along the four wheeler track near the end of Torma Road. Haystack Mountain is a short walk north from Lake 13 Road just west of the bridge over East Branch Ontonagon River.