Gneiss Outcrops SNA

234 Acres Located from Granite Falls, 1.5 mi E, on MN Hwy 212 then S. on Co Rd 40 for 1 mi. Then .5 mile W. on gravel road. Park on shoulder. Chippewa County Twp 115N Rng 39W Sec 11 Type: Prairie Grasslands ECS Subsection: Minnesota River Prairie

Description:

The Gneiss outcrops, formed approximately 3.6 billion years ago, are among the oldest known rock on the earth's surface. This SNA's significance steadily increases as other outcrops along the Minnesota River are exploited for granite mining, housing, and recreational use. These pyramidal outcrops along the Glacial River Warren Valley rise to about 50 feet above the general level of the land, revealing parallel bands of gneisses. Granitic gneiss is light-colored, pink to red; the less common hornblende-pyroxene gneiss is darker, ranging from gray to black. Garnet-biotite gneiss appears in dark and light gray variations. In addition to these metamorphic rocks, the outcrops reveal igneous rock complexes, formed by heat and pressure below the earth's surface. A natural lake lies between the two major rock outcrops, providing a stunning contrast to the adjacent rock cliffs. The very rare Great Plains prickly pear and brittle cactus can be found on dry rock; the rare Carolina foxtail, rare little barley, and mousetail grow in shallow depressions among the outcrops.

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