Dr. Abraham Gesner, Provincial Geologist, visited Grand Manan Island (New Brunswick, Canada) in 1839 to do a geological survey. He found the eastern section is of much older (pre-Acadian) sedimentary rock; the western section is younger (Triassic) igneous (volcanic) rock. Geology Map. The geological contact (or fault) can be seen at Red Point but not at Whale Cove since it is hidden under the beach.   From the parking area a walkway leads to the right and onto the  beach.  Follow along the beach below a cottage to a point where a small brook runs off the cliff (this may dry up in some summers) and large trees begin.  You will find the two geological eras clearly visible in the cliff face. To the left of the dividing line, or geologic contact, you see dark grey lava rock (Triassic); to the right of the line you see the older red rock (pre-Acadian sedimentary). With the use of a magnet, you may collect magnetic sand (magnetite) on the beach.

The western side of the island is mostly high cliffs, 90-120 m (300-400'), composed of basaltic columns.   Columnar basalt is reminiscent of squared timber placed upright side by side.  Other volcanic features include such things as trap rock, sills and intrusions.  The columnar basalt at Southwest Head is actually part of a large sill or volcanic layer.

Glaciation has also left its mark with gravel and sand deposits, and glacial erratics - large granitic boulders scattered about the island including an interesting site - The Upper and Lower Flocks of Sheep at the southern end of the island. Changing sea levels has alternately left beaches exposed or submerged.  A peat deposit and submerged forest can be seen on the water side of Castalia marsh below the high water mark, and a fossil bed of shallow marine life is exposed in the Deep Cove Brook.  Tidal action has been responsible for the barriers or "barachois" (gravel, rock and boulder bars with water trapped on one side) on the western side of the island.  The largest is Dark Harbour Pond.  Smaller versions are present at Long Eddy Point, Indian Beach, Money Cove and other areas along the western side.

Geological formations have given rise to some local names - White Head with its white quartzite head land, Seven Days Work, a cliff face with layers of lava flows pushed apart by igneous intrusions, the Bishop, a rock pinnacle on the northern end of the island, and Southern Cross on the southern end. Unfortunately, erosion has taken its toil on the Cross, only the base of the pinnacle remains. Ongoing erosion is constantly changing the shape of the archipelago (beaches, ledges, cliffs, etc.), and has formed such features as Hole-in-the-Wall.

Rock hounds can find agates, amethysts and zeolites with a little searching. A copper mine operated at Sloop Cove for a few years beginning in 1872, with the copper shipped to England. A limestone deposit is present on Kent Island, extending 201 m (660 feet). The rock is white with yellow and blue veins.

The Grand Manan Museum has a wonderful Geology section donated by the University of New Brunswick Geology Department. A map of the geology of Grand Manan is also available from the New Brunswick provincial government.