Granite Bedrock in Morton, MN
On the westside of town, Morton has a gem… well actually it is granite that you can walk around on. The outcrops are unlike many places to visit with no paved trails or other recreational activities. Instead, visitors can enjoy the 3.6 billion-year-old bedrock next to the Morton Inn with traffic passing through on Highway 19.
About the Outcrops
Known as the “Morton Quartz Monzonite Gneiss”, the Outcrops feature the oldest known bedrock in Minnesota and among the oldest in the world. This scientific and natural area (SNA) has been owned by a few different people and is now owned by the Minnesota Department of Natural Resources (DNR).
As described by the Minnesota DNR, “Classified as “Morton Quartz Monzonite Gneiss,” this scientific and natural area (SNA) features the oldest known bedrock in Minnesota and among the oldest in the world. Rosy-hued Morton gneiss is a type of crystalline granite, characterized by bands of white quartz, pink and grey feldspar, black biotite and amphibole. It was exposed when the torrent of glacial River Warren formed the Minnesota River Valley roughly 10,000 years ago, scouring through glacial drift of the Des Moines lobe and underlying cretaceous sediments to reveal the ancient bedrock. Today, the Minnesota River flows past to the south, a quarter mile away and 100 feet lower in elevation than the highest point of the SNA. But potholes in the rock here are testament to the time when all was submerged by the swirling waters of River Warren.
This site has outstanding biodiversity significance, supporting one of the state's largest and highest quality examples of Crystalline Bedrock Outcrop Prairie (Minnesota River Valley sub-type). Shallow soils on the margins of the bedrock exposures host plants adapted to this drought-prone microhabitat, including rock spikemoss, small-flowered fameflower, little barley, Carolina geranium and brittle cactus. Ephemeral pools in shallow depressions on the rock support a distinct set of species including ovoid spikerush, Carolina foxtail, and flattened spikerush. Small areas of deeper soil support dry to mesic prairie, with Indian grass, big bluestem and prairie dropseed.”
Rare Wildlife Found in the Outcrops
While visiting the Outcrops and the surrounding area in Morton, we encourage you to keep a lookout for these rare wildlife. The regal fritillary (state-listed as special concern), prairie bush clover (state and federally listed as threatened), Wolf's spikerush (state-listed as endangered) and fox snake (a watchlist species) are the four rare species found in this scientific and natural area.