The North Shore Alvar on Kelleys Island is the finest of the few such sites in Ohio. Alvars are horizontal exposures of nearly barren limestone or dolomite which were exposed by glaciers and are kept open by a variety of environmental factors. The name "alvar" is derived from a Swedish word for similar landforms near the Baltic Sea. On Kelleys Island, the alvar is scoured by wind, waves, and ice. Only a few specially adapted plant species can survive in this hostile terrain.
Some of these unusual species on Kelleys Island are northern bog violet,balsam squaw-weed, Kalm's lobelia, and Pringle's aster. The alvar also features shallow glacial striations. Other Ohio alvars are found on the Marblehead Peninsula. Most of these have been disturbed or destroyed by quarrying and other human activities. Extensive alvars are found only in Michigan, New York, and Ontario, Canada.