Geocaching

This EarthCache invites you to visit and learn about the glacial erratic that was left behind in Gonzales Bay. Boulders that are carried by glaciers and left behind when the glacier melts are called erratics. These erratics are often carried from a long way away and often do not resemble the local rock at all. They usually look very out of place.

The erratics in and around Gonzales Bay were placed there during the Frasier Glaciation which occurred between 10,000 and 30,000 years ago. When at this erratic, look towards the south east and you’ll see another erratic deposited by the same glacier (Harpoon Rock) over by Harling point.

If you look closely at the erratic, you will notice that it is nothing like the beach rock on which it sits. The erratic is comprised of Saanich granodiorite which looks very different from the black argillite beach rock that it sits on. The granodiorite is igneous rock formed as molten magma cools very slowly deep within the earth’s crust. Because of the slow cooling, mineral crystals form giving a speckled crystalline appearance. The argillite on the beach is sedimentary rock, formed by mud and silt being compressed into a solid rock under the pressure of hundreds of metres of other sediment that was deposited on top of it.