The ocean’s immense power and unpredictable nature have long captivated human imagination. The concept of an immense wave represents the raw, untamed energy within the world’s waters. This often leads to questions about the most extreme wave events the planet has witnessed.
The Lituya Bay Megatsunami
The single largest wave run-up ever recorded occurred in Lituya Bay, Alaska, on July 9, 1958. This event was a megatsunami, a distinct type of wave caused by massive displacement of material into water. An earthquake, measuring between 7.8 and 8.3 magnitude on the Fairweather Fault, triggered a colossal rockslide.
Approximately 40 million cubic yards (30.6 million cubic meters) of rock plunged from an altitude of about 3,000 feet into Gilbert Inlet, a narrow arm of Lituya Bay. The impact generated a wave that surged up the opposite mountainside to an astonishing run-up height of 1,720 feet (524 meters). This height significantly exceeds ordinary tsunamis and stripped away trees and vegetation over about four square miles.
Megatsunamis differ fundamentally from typical tsunamis because their cause is a localized splash, rather than widespread seafloor displacement from underwater earthquakes. While regular tsunamis can travel across entire ocean basins, megatsunamis are generally localized and result from events like landslides, volcanic eruptions, or meteorite impacts. The Lituya Bay event demonstrates the localized, yet incredibly destructive, power of such a phenomenon.
Categorizing Giant Waves
The term “biggest wave” can refer to different types of phenomena, each with unique characteristics and origins. Tsunamis are primarily caused by underwater disturbances like earthquakes, volcanic eruptions, or large submarine landslides that displace significant water volumes. These waves have long wavelengths and are barely noticeable in the deep ocean, often only a few feet high. However, as they approach shallower coastal areas, their height increases dramatically, sometimes reaching heights of 30 meters (100 feet).
Rogue waves, in contrast, are unpredictable, unusually large surface waves that appear suddenly in the open ocean, often more than twice the height of surrounding waves. Unlike tsunamis, rogue waves are not caused by seismic activity but by complex interactions of ocean currents, winds, and wave systems. Storm waves are another category, generated by strong winds blowing over the water’s surface. Their size is influenced by wind speed, duration, and the distance over which the wind blows.
Measuring Wave Height
Measuring wave height, especially for extreme events, involves various techniques and presents challenges. For ordinary waves and sea states, instruments like buoys and satellite altimetry provide data. Buoys measure the vertical distance between a wave’s crest and its trough. Oceanographers often use “significant wave height,” which is defined as the average height of the highest one-third of waves measured over a specific period.
However, for extreme events like megatsunamis, direct measurement is often impossible due to their sudden and localized nature. Scientists rely on indirect evidence, such as eyewitness accounts and “run-up marks,” the highest points on land reached by the water. The 1958 Lituya Bay event’s height was determined by analyzing the waterline and stripped vegetation on the surrounding hillsides.
Other Notable Record Waves
Beyond the Lituya Bay megatsunami, other wave events stand out for their exceptional size. The “Draupner wave,” recorded on January 1, 1995, in the North Sea, was the first rogue wave confirmed by instrumental measurement. This wave reached 25.6 meters (84 feet), more than twice the significant wave height of the surrounding sea, providing scientific evidence for a previously anecdotal phenomenon.
For surfable waves, Nazaré, Portugal, is renowned for producing some of the largest, amplified by a deep underwater canyon. In November 2017, Brazilian surfer Rodrigo Koxa surfed a wave officially measured at 30.9 meters (101.7 feet), earning a Guinness World Record.
In the open ocean, a buoy in the North Atlantic recorded the largest wind-generated wave at 19 meters (62.3 feet) in February 2013. This represents the highest open-ocean wave recorded by a buoy to date, showing the immense size wind-driven waves can attain.