The word "Dells" came from the French word "Dalles," meaning flat-layered or slab rock. These rock layers formed during the Cambrian period, 500 million years ago, when the North American Continent was completely covered by an ocean called the Cambrian Sea. Layer upon layer of sand and silt built up on the bottom of this ocean, and as the water receded, the mineral layers solidified into sandstone. At the beginning of the Ice Age, approximately 1 million years ago, a series of glacial movements transformed the landscape by tearing off hill tops, filling valleys, and leveling the surface of the earth in the northern and eastern parts of Wisconsin. The Dells lay on the extreme eastern margin of a drift less area that was untouched by the glaciers. However, thousands of years later, when the glaciers began to melt, the water formed enormous and powerful streams that pushed ice, rock, and debris through the sandstone, creating the spectacular rugged beauty of the river shorelines. Today, nature continues sculpturing the Wisconsin Dells with wind, water, and frost to create some of the world's most magnificent scenery.