The Ripple Rock Explosion was set off on April 5, 1958.
The Ripple Rock Explosion was set off on April 5, 1958 at 9:31:02 am.
The Canadian government set off one of the largest, non-nuclear explosions in history, displacing 635,000 metric tons of rock and water in minutes.
Ripple Rock was a notoriously dangerous stretch of water along the Inside Passage water off the British Columbia shores. A pair of underwater mountain peaks created massive shipping hazards that sunk an estimated 20 large and 100 smaller ships and boats between 1875 and 1958. In 83 years, over 100 lives were claimed by this small stretch of water.
Inside Passage BC
Issued in 2003 by Canada Post
Part of the 3rd Tourist Attractions series
Designer: Catherine Bradbury
Ripple Rock was an underwater, twin-peaked mountain in the Seymour Narrows of the Discovery Passage in British Columbia, Canada, a part of the marine trade route from Vancouver and coastal points north. The nearest town was Campbell River. Only 2.7 meters (9 feet) underwater at low tide, it was a marine hazard, described by the explorer George Vancouver as “one of vilest stretches of water in the world.” It was destroyed by a planned explosion on April 5, 1958. This is a National Historic Event in Canada. The Ripple Rock explosion was seen throughout Canada, live on CBC Television. It was one of the first live coast to coast television coverages of an event in Canada.
April 5, 1958 – Ripple Rock Explosion – Campbell River Museum
Circle shows where Ripple Rock was located. It created a navigation hazard in the middle of a major passage.
Previous (failed) attempts to destroy the obstacles were made in 1943 and 1945. A feasibility study was done to figure out a way to blow up the mountains efficiently and safely. The National Research Council of Canada determined the best approach would be a massive, controlled underwater explosion. It took 2 1/2 years to drill shafts and pack 1,270 metric tons of Nitramex 2H explosives along the mountains.
Between November 1955, and April 1958, a three-shift operation involving an average of 75 workers built a 174 meter vertical shaft from Maud Island, a 762 meter horizontal shaft to the base of Ripple Rock, and two main 91 meter vertical shafts into the twin peaks, from which “coyote” shafts were drilled for the explosives. 1,270 metric tons of Nitramex 2H explosives were placed in these shafts, estimated at ten times the amount needed for a similar explosion above water. [ibid]
The Canadian Broadcast Corporation filmed the Ripple Rock explosion from a bunker.
2025’s SOD: