The soils of Pictured Rocks National Lakeshore reflect the area's geologic background, topography, climate, and vegetative influences. The two dominant soil-forming elements are parent material and drainage conditions.
Soil types of the lakeshore can be grouped as upland loams, plains sands, sandy loams and sands, upland stony loams and sands, lakeshore soils, swamp and wetland soils, and organic soils.
Upland loam soils are underlain by gravels at 15 to 30 cm (6 to 12 inches), with stony clays below gravel. They are generally well drained in surface layers and are moderately productive. The soils are distinguished by large amounts of limestone in the lower gravels. Local areas are stony. Upland loams occur in the southwestern portion of the lakeshore.
Most of the plains sands occur in land that is level to slightly rolling. All these soils are underlain by dry loose sand several feet deep. These soils are well drained and low in fertility. Plains sands occur throughout the Kingston Plains (outside the park) and extend into the southeastern and southcentral portions of the inland buffer zone. Intense burning that occured during the logging era of the past century greatly impacted the soil in the Kingston Plains area, and affects what grows there today.
Hilly terrain and stony conditions occur throughout the sandy loams and sands soils. The surface soils, 30 to 40 cm (12 to 16 inches) deep, are underlain by leached sands, which are easily penetrated. Some clays occur locally in the subsoil. Sandy loams and sands soils occupy the comparatively high, hilly upland areas in the eastern sections of the lakeshore, in the western portion of Beaver Basin, and southwest of Sand Point.
Bedrock (sandstones and limestones away from Lake Superior) is present at slight depth throughout upland stony loams and sands. The profile is poorly developed, stones are very common, and many inclusions of clay and clay hardpan are present. Upland stony loams and sands soils are present in the rolling terrain from Beaver Lake to Sand Point.
Sand, gravels, and stones are indicative of lakeshore soils. They are generally excessively dry due to rapid subsurface drainage. Active and stabilized dune areas are included. Lakeshore soils occur at Sand Point and extensively along the northern shore of the national lakeshore from Miners Beach to Sable Creek.
Swamp and wetland soils have black muck surface layers with clay or sand beneath. The water table is from .3 to 1 m (1 to 3 feet) below the surface, and the soils are almost permanently waterlogged. Water-tolerant trees, shrubs, and herbaceous plants grow well in these soils. Swamp and wetland soils are present in bogs, marshes, and in narrow floodplains along major stream channels.
Organic soils are mucks and peats up to ten feet deep. Water-tolerant vegetation grows well in this soil type.