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damaged a lifeboat that was supported 27 feet above the waterline. In its loaded state, the cargo deck of the Fitzgerald was only 12 feet above the waterline.
Around 7:00 P.M. the Fitzgerald disappeared from the Anderson’s radar screen. The last word from Captain McSorely on the Fitzgerald was: “We’re holding our own.” After the vessel sank, underwater inspection revealed that she had broken in two at about the one-third, two-thirds point. Various theories have been put forth as to the cause of the breakup, including the possibility that some of the Fitzgerald’s hatches were not sealed, allowing the vessel to take on water.
However, Captain Cooper made an interesting point in his recounting of the storm. He stated that around 7:00 P.M. the Anderson took two huge waves in rapid succession, the first flooding the deck, the second throwing green water up on the bridge deck. He speculated that these waves (remember, they were probably traveling at around 38 knots) overtook the Fitzgerald a few minutes later and, if joined by a third rogue wave, might have overpowered the struggling vessel—evidence of an occurrence of the Three Sisters in a Great Lakes storm.21
CONTINENTAL SHELVES AND SHALLOW SEAS
The third source of extreme waves is wind-driven waves piling up in shallower waters such as those of the continental shelves or the North Sea, where depths are 100 to 650 feet. This is similar to the phenomenon of waves on a beach—waves increasing in height as the water becomes shallow. An extreme wave can cause flooding in coastal areas when a wall of water inundates the shore for several minutes, or even tens of minutes, or occurs as a low-frequency wave train with a period of 30 seconds. Extreme waves pose a hazard to marine structures other than ships, examples being ports, harbors, piers, and offshore oil platforms. Notable examples include the loss of Texas Tower 4 in the North Atlantic and the loss of oil platforms in Canada and the North Sea.
In the 1950s, the U.S. Air Force planned to build five offshore platforms along the East Coast of the United States. Because of their similarity to offshore oil platforms in the Gulf of Mexico, they were called “Texas Towers.” The towers were built as part of the U.S. early-warning