National Treasure #170: The Detonation of Ripple Rock


Maybe blowing up underwater rock peaks seems like an odd treasure, but it removed a hazard to navigation that had claimed or damaged about 120 vessels and killed at least 114 people. At the time, in 1958, it was the largest non-nuclear explosion ever. It’s a National Historic Event.

Historical plaque overlooking Seymour Narrows and site of Ripple Rock.

The History Behind the Plaque

  • 1792 – Captain Vancouver identified the hazard when charting the Seymour Narrows, a nasty stretch of water between Vancouver Island and the mainland.
  • 1931 – A marine commission recommended the removal of Ripple Rock.
  • 1942 – The government authorized attempts to remove it.
  • 1943 – An attempt with floating drilling barges failed when the cables anchoring the barges kept breaking.
  • 1945 – An attempt with overhead cables also failed.
  • 1953 – The National Research Council commissioned a feasibility study.
  • 1955 – 1958 – About 75 hard-rock miners worked in three shifts to drill shafts down (500 feet) and then laterally under the sea bed (2,300 feet) and up into the peaks, and to stuff them with explosives.
  • 1958, April 05 at 9:31:02 – Ka-boom!

Watching the Event

It was the first nationally televised live event on CBC, but the magic of the internet means that if you missed it then, you can still see it now.

The explosion itself (2:33)

Some history (27:19)

Or you can check out the page on Ripple Rock from the Museum at Campbell River.



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4 Responses to National Treasure #170: The Detonation of Ripple Rock

  1. Ralph Gibson says:

    I remember watching this on TV , I think at home.

  2. Barry says:

    Interesting that a 25′ tidal wave did not cause damage. How/what/how do you consider damage to count?

    • Isabel Gibson says:

      Barry – I guess they counted some marine life . . .
      “No damage was sustained. Careful monitoring by the Fisheries Department found that five orca, a school of porpoises, two sea lions and one fur seal seen near the area before the explosion were all seen again afterward.”
      I dunno about the partridge in the pear tree.

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