Saint Croix State Park - Natural History

Natural History

The St. Croix River Valley was carved by meltwater during the last glacial period 10,000 years ago. The water deposited a variety of sediments, which compose over 30 different types of soil within the park. Some soils are very sandy while others are made of red or yellow clay. The historic Yellowbanks area of the park is named for its distinctive deposit of yellow clay exposed by the St. Croix River. The bedrock of the area is mostly buried under 75 to 100 feet (23 to 30 m) of these glacial till deposits. However the underlying basalt and sandstone is exposed in one area along the Kettle River known as the Highbanks, where a final ancient flood of meltwater scoured away the sediments.

In addition to the two rivers, at least ten other streams flow through the park, creating a watershed of hundreds of square miles.

St. Croix State Park is located on the eastern edge of the Mille Lacs Uplands. Initially dominated by red and white pines, the vegetation has been altered by logging and farming. The present secondary forest is a mix of pines, black spruce, sugar maple, and basswood. More open areas form meadows, oak savanna, and jack pine barrens. Numerous lakes, marshes, and streams support wetland and riparian zone plants. Wetlands with no outlet and high acidity support tamarack bogs.

Large mammals found in the park include eastern timber wolves, black bears, white-tailed deer, coyotes, beavers, raccoons, and gray and red foxes. Birds include the ruffed grouse.

A tornado hit part of the park on July 4, 1977. Straight-line winds toppled trees over hundreds of acres on July 11, 2008 and again on July 1, 2011. In the latter storm, many of the historical structures were damaged. However there were no injuries as the park was closed due to the 2011 Minnesota state government shutdown.