Castle Rock EarthCache

You are standing on what was once the bottom of a great lake. Glacial Lake Wisconsin was a short-lived prehistoric glacial lake that existed from approximately 15,000 to 19,000 years ago, at the end of the last Wisconsin ice age. The lake was located in the "central sand plains" ecoregion of the state. This portion of the state is generally a flat, sandy lake plain which was formed in and around Glacial Lake Wisconsin.

The soil here is primarily sandy lake deposits. Sandstone buttes carved by rapid drainage of the glacial lake, or by wave action when they existed as islands in the lake, are distinctive features of this landscape. The lake began its formation when ice from the Green Bay Glacial Lobe came into contact with the Baraboo Hills in southwestern Wisconsin. This contact blocked the south-flowing Wisconsin River and due to higher topography on the lakes other margins it continued to fill fed by meltwater from the Wisconsin River.

At its peak Glacial Lake Wisconsin was up to 150 feet in deep and covered over 1,825 square miles. Today lake deposits are covered in many places by glacial outwash, dune sand, peat and muck. Many of the swamps, marshes and bogs of central Wisconsin were formed as a result of the accumulation of the Lake's more impervious deposits after the last glaciation.