The question of the tallest wave ever recorded does not have a single, simple answer because different types of waves are measured under vastly different circumstances. Waves generated by geological events, such as landslides, are measured differently than those created by wind in the open ocean. The record holder depends entirely on the definition of a “wave” and the method used to quantify its height, leading to records that are incomparable.
The Definitive Record Holder
The largest wave event in recorded history occurred in Lituya Bay, Alaska, on July 9, 1958. This event was a megatsunami, not a typical wind-driven wave, caused by a massive geological disturbance. A magnitude 7.8 earthquake on the nearby Fairweather Fault triggered a colossal rockfall of approximately 90 million tons into the narrow inlet of Gilbert Inlet.
The impact of this rock mass plunging from about 3,000 feet created an instantaneous displacement of the fjord’s water. This resulted in a localized surge that splashed up the opposite mountainside to an elevation of 1,720 feet (524 meters). This figure is known as the “run-up height,” which is the maximum vertical distance the water reached on the land above sea level. This remains the highest run-up ever documented for a wave event.
How Extreme Waves Are Measured
Scientists use distinct methodologies to measure wave height, depending on the wave’s origin and location. Run-up height is used for megatsunamis, representing a post-event measurement based on evidence like scour lines and destroyed vegetation. This measures the vertical reach on land, not the height of the wave crest in the water.
The standard measurement for ordinary wind-generated ocean waves is the Significant Wave Height (\(H_s\)). This statistical value is defined as the average height of the highest one-third of waves in a given sea state, and is used by meteorologists in marine forecasts. A third measurement, Maximum Wave Height, is the true peak-to-trough height of a single wave, which can be nearly double the \(H_s\). These ocean measurements are captured by instruments such as deep-sea buoys, satellite radar altimeters, or pressure sensors on offshore platforms.
The Tallest Waves in the Open Ocean
Instrumental records in the open ocean reveal wave extremes known as rogue waves. These waves appear unexpectedly and are at least twice the height of the surrounding significant wave height.
The first scientifically recorded rogue wave was the Draupner wave, which struck a gas platform in the North Sea in 1995. Measured by a laser sensor, it reached a maximum height of 84 feet (25.6 meters) from trough to crest, more than double the significant wave height of approximately 39 feet (12 meters) at the time.
More recently, the Ucluelet wave was recorded by a buoy off the coast of British Columbia in 2020 at 58 feet (17.6 meters). While shorter than the Draupner wave, the Ucluelet wave was nearly three times the height of the surrounding waves, making it proportionally the most extreme rogue wave ever recorded.
Mechanisms Behind Monster Waves
The formation of giant waves is driven by two fundamentally different physical processes. Megatsunamis and localized tsunamis are created by massive displacement events. This occurs when a large volume of water is abruptly pushed aside by an external force, such as an underwater earthquake, a submerged landslide, or a subaerial rockfall.
These waves are not propelled by wind and are characterized by extremely long wavelengths, allowing them to travel across entire ocean basins with minimal height loss in deep water.
Rogue waves and large storm waves, conversely, are generated by complex fluid dynamics and constructive interference. Constructive interference happens when multiple wave crests, or wave trains, traveling at different speeds and directions align, briefly merging their energy into one towering wave. This energy focusing can be amplified by strong ocean currents running counter to the wave direction, which shortens the wavelength and causes the wave to rapidly increase in height. Nonlinear effects, where energy is exchanged between different wave components, also play a role in their unpredictable and rapid formation.