Seawall

The exposed bedrock at the seawall is much different from the rugged granite cliffs on the eastern side of the island. It’s an extrusive igneous tuff that originated some 400 million years ago when volcanic eruptions produced clouds of light gray layers of fine ash that settled on the ocean floor, and then was transformed by pressure and heat. Geologists call these stratified rocks the Cranberry Island Series. (The bedrock of the Cranberry Islands just offshore from the seawall also consists of the Cranberry Island Series. Duh.)

The dominant tree along this shoreline is white spruce, and the interior of the Seawall area mostly consists of peatland created by maritime weather: fog, clouds, mist, and rain. Both spruce and peatland generally are found only farther to the north, evidence again of Mount Desert Island’s unique location between the land and the sea, and between the northern Arctic and southern temperate zones.

When the Cranberry Island Series was created way back in the Siluro-Devonian period, seaweed was the dominant form of plant life on Earth.