Thursday, March 31, 2011

Ripple Rock 1958 (Canada) - Giant Demolition Explosion

"As early as 1931, a Marine Commission recommended removing Ripple Rock, but it was not until 1942 that the government authorized attempts to remove it. There was political opposition to the destruction of Ripple Rock, as some felt it would serve well as a bridge support to connect Vancouver Island to the mainland.

The first attempts at planting explosive charges on Ripple Rock were made with floating drilling barges with the goal of blasting away the rock in pieces. The first, in 1943, was secured with six 3.8 cm steel cables attached to anchors that altogether weighed 998 metric tons. This approach was abandoned when one cable broke on average every 48 hours. Another attempt in 1945, involving two large overhead steel lines was similarly abandoned after only 93 (out of 1500 planned) controlled explosions were successful.

In 1953, the National Research Council of Canada commissioned a feasibility study on the idea of planting a large explosive charge underneath the peaks by drilling vertical and horizontal shafts from Maud Island in the sound. Based on the study, this approach was recommended. Dolmage and Mason Consulting Engineers were retained to plan the project, and three firms, Northern Construction Company, J.W. Stewart Limited, and Boyles Brothers Drilling Company, were granted the contract, which ended up costing in excess of 3 million Canadian dollars."

"Between November 1955, and April 1958, a three-shift operation involving an average of 75 men worked to build 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.

The explosion took place at 9:31:02 am on April 5, 1958. 635,000 metric tons of rock and water was displaced by the explosion, resulting in debris at least 300 meters in the air, falling on land on either side of the narrows. The blast increased the clearing at low tide to about 14 meters (45 feet).

The Royal Canadian Mounted Police cleared the area of within 3 miles of the explosion, and the engineers and TV crew that witnessed the explosion were housed in a bunker.
The explosion was noted as one of the largest non-nuclear planned explosions on record, though Soviet authorities reported a larger explosion in the Ural Mountains to carve a new channel for the Kolonga River and in China to open a copper mine."

At more than 1 KT, this is clearly a massive explosion. Similar to operation sailor hat, but considerably more powerful. Even larger tests were conducted by various nations over the years, particularly American tests such as the Misty Castle test series which had conventional blasts up to about 4 KT. These tests were used to simulate nuclear explosions aboveground, at a time when only underground tests were allowed.

"Misty Picture" explosive charge

There was also a larger test called Minor Scale seen below:

Minor Scale was probably the largest non-nuclear (intentional) explosion ever.
There is also a test report for Minor Scale.

Finally, there was Minor Uncle, the last of the blasts over 2 KT:

Minor Uncle, one of the last large-scale simulated nuclear blasts (but still using conventional explosive), was undertaken in 1993. "The MINOR UNCLE test was executed on 10th June, 1993, at 0910 hrs Mountain Daylight Time at the Permanent High Explosive Test Site (PHETS) site , White Sands New Mexico. The event simulated a 4 kt nuclear detonation (the simulation was most accurate in the 7 kPa overpressure region) by detonating a hemispherical charge of 2472 tonnes of ammonium nitrate and fuel oil (ANFO) mixture initiated by a 125 kg octol booster. The charge which was detonated at its center, was contained by a fibreglass hemispherical shell which was located at ground zero." Minor Uncle information at

It is unclear if any industrial accidents have been larger in yield than 4 KT, though many have come close. One possible, highly speculative estimate, puts the Kuybyshev Ufa train disaster, a natural gas explosion, at 10 KT. There is little in the way of confirmation for this, however. The brissance of natural gas is generally much lower than high explosives.

For more giant explosions, visit the List of the Largest artificial non-nuclear explosions. And also

Check out the images from some other tests:

Misers Gold - 2.5 KT

Direct Course - 600 T

Sadly you can only read 8 Global Security articles before it forces you to log out. That may be motivation for me to sign up and pay them, or more likely motivation to copy the images and text so that I can use it later. :( Charging for internet content seldom works out.

1 comment:

jsauer000 said...

Misty Picture was an 8Kt sim, Misers Gold, 4 Kt.