Click here to skip to the content

Grand Manan Volcanic Rocks

Grand Manan Island has two distinct geological landscapes. The eastern side of the island is composed of metamorphosed Cambrian sedimentary and volcanic rock formations. Volcanic rocks from the Triassic period make up the western portion of the island. The Triassic basalts on Grand Manan are part of the North Mountain Basalt, created from lava flows that covered the entire Bay of Fundy basin at one time. The North Mountain basalt was formed in a volcanic event preceding the breakup of the supercontinent Pangaea in Early Jurassic time. These basalts form some of the well-known landscapes in Grand Manan. The “Seven Days Work” cliff, the beach at Whale Cove, and the tall basalt column cliffs of Southwest Head are all examples of this geology. Columnar basalt looks like squared timber standing on end side by side. Gas bubbles within the basalt provided growth chambers for crystals as the rock cooled. Cavities contain the silicate minerals heulandite and stilbite. The columnar basalt at Southwest Head is New Brunswick’s older version of spectacular the Giant’s Causeway in Northern Ireland.