N A T I O N A L   P A R K S


A billion years ago sand was carried from southern Minnesota via braided streams and deposited in a large, shallow basin. Over eons that sand was cemented into sandstone. That sandstone now underlays the Apostle Islands National Lakeshore. Geologic forces have pushed up the basin and today sandstone cliffs and rock formations are seen throughout the park. Reentrants are interesting features of sandstone cliffs which are eroded by wave actions. Softer layers are carved more quickly by waves, causing the layer to become eroded back into the cliff. Reentrants which are joined can form caves and arches and other features. 

Below are images of sea caves and bluff walls which give an impression of the abundant colors and textures one can appreciate on a quiet walk. Lichens and moss grow on the surface of ancient beaches and dunes and other formations. Since life as we know it did not exist then, the preserved formations contain no fossils.

Since the interiors of caves can be quite dark, it is most helpful to carry a tripod on your excursion. Shooting at the highest resolution and fidelity may mean exposures of several seconds or more. To make your trip safer, wear crampons.