lake superior swirly blue water

america basalt bedrock blue cliffs coast coastline color colorful curves forest freshwater gabbro geologic geology great green horizon igneous lake lakes land landscape largest material mesoproterozoic midcontinent midwest minnesota nature north pattern phaneritic picturesque ridge rift ripples rock rocky rough rugged sedimentary sediments shore shoreline stone summer superior swirls swirly tofte trees valley vivid water waves