58:7.7

There are few places on the earth where such activities are more graphically shown than in the St. Croix valley of Wisconsin. In this region there occurred one hundred and twenty-seven successive lava flows on land with succeeding water submergence and consequent rock deposition. Although much of the upper rock sedimentation and intermittent lava flow is absent today, and though the bottom of this system is buried deep in the earth, nevertheless, about sixty-five or seventy of these stratified records of past ages are now exposed to view.