“Reefs” & Wrecks

The Portage Lake Volcanics forms reef-like ridges where resistent layers are being eroded by the shorelines, and this creates spectacular diving spots, where divers can visit the many shipwrecks which litter the area, both at Isle Royale and along the Keweenaw.

“Reefs”seen from space imagery at the offshore harbor entrance of Eagle Harbor

Shipwrecks  NPS
Barge of the City of St Joseph, aerial view on calm day, on “reef” of Lake Shore Traps near Grand Marais, 1 km E of Eagle Harbor.

Neil Harri Photohttp://www.neilharriphotos.comshapeimage_4_link_0
Magnetic anomalies are interpreted to be lava flow layers, which likely make “reefs”.