Victoria EarthCache Series #2: Devilfish Rock
In British Columbia, Canada
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This erratic is located on a beach below the high water mark. You will need to access this area at LOW tide to achieve the requirements to successfully log your visit.
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.
The canine landshark sniffing at the sea-stuff rotting on the argillite
Local First Nation people have passed on stories about the erratic in Gonzales Bay. Giant Pacific Octopus (known as devilfish to the First Nation people) use this area as a spawning ground. According to legend, if you touch the aptly named Devilfish Rock, devilfish would come up from the sea. You’ll have to go out there at low tide, but we encourage you to go out and touch the rock to see what happens!
An interesting note: The Giant Pacific Octopus is very high in protein. In addition to hunting the Giant Pacific Octopus for food, the First Nation people also used the fresh tentacles as bait for halibut fishing. The tentacles were stripped and creatively wrapped to resemble baby octopus which were strung on their hooks for fishing.
Lesson: You need to take three photos to show you understand the topics discussed above:
- Take a close up photo showing that you’ve observed the crystalline structure of the igneous erratic. If you can, identify a couple of the minerals in the rock (bonus points).
- Take another close up photo of the sedimentary argillite. If you can find hints of its silt/mud origins such as other small stones embedded in the argillite, then photograph those.
- Take a photo of you and your GPS with devilfish rock.
(No hints available.)
Last Updated: on 8/24/2017 9:10:46 PM Pacific Daylight Time (4:10 AM GMT)
Coordinates are in the WGS84 datum