Later there was a mountain making movement of the earth and there appeared peaks as lofty as those in the Alps or Rockies. The once horizontal beds of sand, clay, limestone and iron were uplifted and folded in the process, the layers at the lake being inclined about fifteen degrees as seen along the East Bluff. The Baraboo Bluffs are among the oldest formed things on the globe—older than the Rockies or Alleghenies, older than a pound of coal on the earth, older than any tree or bird or beast that ever lived.
There was a long period of erosion and a river cut a gorge through the range where the lake is now located.
In Paleozoic times the sea returned again, the tops of the bluffs stood as islands above the waves, the loose rocks were rounded on the shore, and sandstone almost filled the gorge where there was once a river. The animal life then consisted of trilobites, oyster like organisms, and other low forms.
The sea retreated and a river once more carried away the material which filled the gap in the bluffs. Because the hills of this region were once buried and again exposed to view, they are sometimes called the "Baraboo fossil."
The Glacial Epoch
Next came the glacial epoch, when the advancing ice from the northeast came into the Baraboo region; this was a long time after the sea retreated the last time, possibly a period of 100,000 or 200,000 years. Into this gorge where probably once flowed the stream we now know as the Wisconsin River, the ice advanced to the terminal moraine, where the visitor descends just before reaching the lake. At the same time another tongue of cold crept into the valley between the Devil's Nose and the Lake. Had the tongues of ice advanced much farther there would have been no lake. Sand and gravel were washed into the gorge, leaving a deposit hundreds of feet thick. The well at the north end of the Lake is 283 feet deep, the drill stopping before it reached the bed of the ancient stream. In times agone the river must have found its way through a chasm 900 or 1,000 feet deep, a scene as picturesque as that of the present gorge below Niagara Falls.
The Lake at Present
The following applies to the lake as it is today:
Above sea level—About 960 feet.
Above the river at Baraboo—About 120 feet.