Surficial Geology

Surficial geology describes the composition of the layer of unconsolidated material between bedrock and the surface of the ground. When the mile thick Wisconsin glacier moved across the area during the Pleistocene Epoch 75,000 years ago it scraped vast amounts of rock and sand form the surface of the mountains. Melting water from the glacier moved some of this material downstream leaving deposits of sand and gravel along the way. These deposits formed the stratified drift aquifers that are our primary source of groundwater.

As the last of the glacier melted 12,000 years ago it left behind a mantle of debris. The depth of this soil mantle varies throughout Eaton depending on soil type and the steepness of slopes. Approximately 80 to 90 percent of Eaton has a soil cover that is less than 5 feet thick. This imposes limits on the possible location of septic systems and on excavations for roads and buildings. Deeper soils are found mostly along the valley bottoms.

As you can see in the map below most of Eaton is shaded green which represents an unsorted mixture of gravel, sand, silt, and clay. The blue areas labeled Qs are poorly drained swampy areas consisting of peat, silt, and clay. All the other areas are predominantly composed of sand and gravel. The dark purple ones labeled Qd are undifferentiated mixes. The rest are distinguished by their shape. The dark pink areas labeled Qk are hilly deposits. The light pink Qkt are fairly flat. The bright pink area in the southwest jutting into Purity Lake is a narrow ridge. The Qkf area next to it has a mix of small holes and mounds. The Qf area to the west of Crystal Lake is a fan shaped deposit of gravel, sand, silt, and clay.