Waves are a powerful natural phenomenon, capable of immense scale and destructive force. Some reach extraordinary sizes, highlighting the dynamic power of oceans and the diverse mechanisms that generate such colossal forces.
The Lituya Bay Megatsunami
The largest wave ever recorded occurred in Lituya Bay, Alaska, on July 9, 1958. This megatsunami was a highly localized splash-up caused by a massive landslide. A magnitude 7.8 to 8.3 earthquake along the Fairweather Fault triggered approximately 40 million cubic yards (30.6 million cubic meters) of rock and glacial ice to plunge from about 3,000 feet (914 meters) into the narrow Gilbert Inlet.
The immense impact displaced water, generating a wave that crashed against the opposite slope of the inlet. This surge, or run-up, stripped away trees and soil to an astonishing elevation of 1,720 feet (524 meters) above sea level on a spur of land directly across from the landslide. This height is greater than any other recorded wave event globally. The wave traveled down the bay, diminishing in size, but still caused substantial damage and resulted in five deaths, including two individuals on a fishing boat. The Lituya Bay event demonstrated how localized, massive disturbances can create waves of unprecedented scale.
Understanding Extreme Wave Formation
Extreme waves form through various mechanisms, beyond typical wind-driven swells. Tsunamis are caused by large-scale disturbances that rapidly displace significant volumes of water. These disturbances often include undersea earthquakes, especially powerful megathrust earthquakes at tectonic plate boundaries. Volcanic eruptions and large submarine landslides can also generate tsunamis by moving vast amounts of water.
In the open ocean, tsunamis have long wavelengths and are often barely noticeable. However, as they approach shallower coastal areas, their speed decreases while their height dramatically increases, leading to destructive surges.
Rogue waves, also known as freak waves, are unusually large, spontaneous surface waves that appear unexpectedly in the open ocean. They are defined as waves whose height is more than twice the significant wave height of the surrounding sea. One common explanation for their formation is constructive interference, where multiple wave crests traveling at different speeds and directions align and combine their energy, momentarily creating a much larger wave. Rogue waves can also form when waves interact with strong ocean currents, which can shorten wave frequency and cause waves to dynamically merge.
Wind-generated waves are the most common type of ocean wave, formed by the transfer of energy from wind blowing across the water’s surface. The size and characteristics of these waves depend on factors such as wind speed, duration, and fetch (the distance over which the wind travels across the water without obstruction). While most wind waves are relatively small, prolonged strong winds over large areas can generate substantial waves. Unlike tsunamis or rogue waves, wind waves are a continuous process of energy transfer from the atmosphere to the ocean surface.
Other Significant Large Waves
While Lituya Bay holds the record for highest run-up, other large wave phenomena are significant for different reasons. The Draupner wave, recorded on January 1, 1995, in the North Sea, was the first instrumentally confirmed rogue wave. Measuring 25.6 meters (84 feet) in height, it provided scientific evidence for a phenomenon previously considered folklore among sailors. Its measurement advanced the study of unpredictable, unusually large waves in the open ocean.
Major tsunamis, while not reaching Lituya Bay’s splash-up height, have had far more widespread and devastating impacts. The 2004 Indian Ocean Tsunami, triggered by a magnitude 9.1 earthquake off Sumatra, caused immense destruction across 11 countries. Waves, reaching 30 feet (9 meters) or more at the shoreline, traveled across the Indian Ocean, resulting in over 225,000 fatalities. This made it one of the deadliest natural disasters in recorded history.
Similarly, the 2011 Tohoku Tsunami in Japan, caused by a magnitude 9.0 earthquake, generated waves up to 40.5 meters (133 feet) high in coastal areas like Miyako. This tsunami devastated a 2,000-kilometer (1,242-mile) stretch of Japan’s Pacific coast and caused a severe nuclear accident at the Fukushima Daiichi power plant. These events demonstrate the catastrophic reach and power of tsunamis generated by large seismic activity, even if their wave heights are measured differently than the localized Lituya Bay megatsunami.
For surfers, the largest rideable waves are found in locations like Nazaré, Portugal, where Sebastian Steudtner successfully surfed an 86-foot wave in 2020. Other notable big wave surfing spots include Jaws in Hawaii and Mavericks in California, known for their powerful, towering swells.