Thunder Mountain

State Natural Area (No. 491)

Location: Within the Chequamegon-Nicolet National Forest. Oconto County. T33N-R17E, Sections 25, 36. 75 acres.

Access: From the intersection of State Highway 32 and County Highway W in Mountain, go east on County W 8.5 miles, then north on FR 2101 (La Fave Road) 4.6 miles. Walk east and north on a trail 0.8 mile, then head due east 0.2 mile into the site.

Description: Thunder Mountain is a quartzite monadnock that rises 360 feet above the wetlands at its base and affords picturesque views of the surrounding Forest. It is one of the largest of several promontories in the southern portion of the Nicolet National Forest that are not drumlins, but are bedrock outcrops, predating the Pleistocene, actually of the Precambian era, dating to the early and middle Proterozoic division. It has exposed bedrock on the southern flank, and these contain specimens of Missouri rock-cress (Arabis missouriensis), a rare plant. Two other rare plants are found on the mountain, butternut (Juglans cinerea) and Indian cucumber-root (Medeola virginiana). Several spring seeps are on the mountainside. The forest on the slopes is more southern in its biota than normally found on the Nicolet. It is classed as a southern dry-mesic forest, dominated by regenerating red oak and white oak, especially on the south facing slopes. The lowlands at the base contain white cedar and black ash swamps, a river corridor, and a small silver maple floodplain forest. Other notable species include the parasitic plant squaw-root, and turkey vulture. Thunder Mountain is owned by the US Forest Service and was designated a State Natural Area in 2007.