Wellness Esker At St. Croix Falls

Geomorphology in the Backyard

In the heart of St. Croix Falls, Wisconsin, lies a glacial treasure. Wellness Esker is one of the highest eskers in the state of Wisconsin. At almost 40 meters (~130 feet), it towers above the city below, creating a breathtaking view of the St. Croix River valley, the surrounding bluffs, and across the state border into Minnesota. The base of Wellness Esker itself juts up against local residents property on the west side, and practice fields for local sports teams to the east. Wellness Esker has been designated as part of the state wide Ice Age Trail system, connecting the frontal boundaries of the extent of the last glaciation, and is just minutes from a rare geologic wonder, Interstate Park, where the earth is permantely morphed by the catastrophic flooding of a prehistoric glacial lake.

A River Runs Through It

An esker is a fluvioglacial deposit formed inside of a glacier. The ice that is creeping across the surface of the earth becomes stagnant, and the bottom layer has possibly frozen solid to the ground. Meters up on the surf, the sun and changing temperatures create melting ice with water flowing, creating channels into the ice. This flowing water carries sediment from the surface in its load, and also collect sediment as it carves downward through the ice. This material builds up along the bottom of the channel and creates a river bed of glacial deposits. As the main body of ice gradually recedes northward, the im beneath these glacial rivers melts, deposting the fertile sediment into a snake-like hump in the topography. Since it is a fluvial feature, the sediment inside the esker is rounded and sorted from being carried through the waters and bouncing off the ice, creating stratified layers of sediment.

The Official State Glaciation

Wellness Esker was formed during the last glaciation in the state of Wisconsin. Since glaciations tend to be named where they advance from, that period of ice movement was given the name Wisconsonian. The formation of Wellness Esker was caused by the Grantsburg Lobe, a faster moving section of the Superior Lobe ice sheet, advancing into Wisconsin from northeast Minnesota, which caused the St. Croix River to be dammed by ice. This occurred a short 13,000 years ago. The ice sheet itself did not recede from Wisconsin until only 10,000 years ago, as it backed its way up to Canada through what is now Lake Superior. The sediment inside the glacier is composed of gray calcareous soils from the Canadian prairie and North Dakota plains. These materials were carried inside of the ice, or along the top of the sheet as the ice itself gouged through the bedrock and upper layers of these northern regions.

More Than Just King of the Hill

Some people may be at a loss as for what to do with a large reminder of the last time the area was covered in ice. For many years, the sediment has been mined for gravel to use in construction. This gravel is transported to the Twin Cities to be converted into cement for the constant building boom in that area. A hiking trail climbs the spine of the esker, providing panoramic views of the St. Croix River to the west, and the flat hummockey terrain of western Wisconsin. Slowly, Wellness Esker is shrinking. The years of mining have stripped many layers of gravel from the area, and natural erosion from freeze thaw processes, water runoff, and human interaction are slowly removing the outermost layers of soil, and depositng them in the land beneath the esker.