Hampton Roads Naval Museum

48. Mines in WWI

Norfolk, VA

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Mines are effective in naval warfare because they are not seen until the mines are almost upon a ship's hull. The effectiveness of a mine depends on its being invisible to its target. A submerged mine has the advantage of striking a ship where it is most vulnerable, the underwater portion of the hull. Mines are only effective if they are submerged enough under the water so a passing ship will sail into it, setting off the firing mechanism. Stealth is the principal advantage to undersea weapons. The Mk 6 mine, as you see on display in the museum, played an important role during World War I by protecting allied shipping. In 1918, the United States and British navies planted more than 76,000 Mk 6 mines in the North Sea. This mine barrage limited the ability of German subs to break out of the Atlantic Ocean and attack Allied shipping. The Mk 6 mine was a moored contact mine. This mine was dropped from rails off the stern of surface vessels in water 30 to 3,000 feet deep. The mine carried 300 pounds of TNT. Detonation occurred when a ship or submarine came in contact with the copper antenna connected to a float above the mine case. Detonation could also occur if a submarine encountered one of the two hertz horns located on the case, thus breaking a glass tube that released electrolyte and completed the firing circuit.