The question of when the “biggest” tsunami in history occurred depends entirely on how the term is defined, as the biggest wave height, the most widespread destruction, or the greatest energy release are all measured differently. A tsunami is a series of ocean waves caused by the rapid displacement of a large volume of water, typically resulting from a sudden geological event. These waves can travel across entire ocean basins.
Identifying the Largest Measured Wave Height
The largest physical wave height ever directly measured is attributed to a localized event known as a megatsunami, which is distinct from a typical tectonic tsunami. Megatsunamis are massive splash events caused by a large mass of material falling into a body of water, producing initial wave amplitudes far exceeding those of earthquake-generated waves. The most significant recorded instance occurred in Lituya Bay, Alaska, on July 9, 1958.
A magnitude 7.8 to 8.3 earthquake along the Fairweather Fault triggered a massive rockfall of about 30 million cubic meters of rock and glacial ice into the narrow Gilbert Inlet. The colossal impact generated a wave that surged up the opposite slope, reaching an incredible run-up height of 1,720 feet (524 meters). Run-up is the maximum vertical height the water reaches above sea level on the land, and this measurement remains the highest ever recorded for any wave event.
This extreme height was caused by the confined geometry of the fjord, which concentrated the energy from the landslide. Although the wave was the tallest on record, its destructive force was highly localized, stripping trees and soil from the steep slopes around the bay down to the bedrock. The event resulted in the deaths of five people, but it did not cause the widespread, trans-oceanic devastation of a major tectonic tsunami.
The Most Powerful and Destructive Tectonic Tsunami
When considering the most powerful tsunami in terms of energy release, geographical reach, and human cost, the focus shifts to events caused by submarine earthquakes along tectonic plate boundaries. The primary example is the 2004 Indian Ocean Tsunami, triggered by the Sumatra-Andaman earthquake on December 26, 2004. This event registered a magnitude between 9.1 and 9.3, making it one of the largest earthquakes ever recorded.
The undersea megathrust earthquake caused the longest fault rupture ever observed, displacing the seafloor vertically over a length of 1,200 to 1,300 kilometers. This immense movement displaced the entire water column above it, generating a tsunami that radiated outward across the Indian Ocean. Waves as high as 30 meters (100 feet) were recorded in the hardest-hit areas, particularly in Aceh, Indonesia.
The tsunami’s energy traveled thousands of kilometers, affecting 14 countries from Southeast Asia to the east coast of Africa. Waves reached Sri Lanka and India about two hours after the quake and were observed along the African coast more than seven hours later. The sheer geographical extent and the lack of a comprehensive warning system contributed to a death toll estimated at least 227,898 people.
Prehistoric and Ancient Gigantic Tsunami Events
The question of the absolute biggest tsunami, in terms of total energy and global impact, must look to events that predate human recorded history, which are studied through geological evidence. These events represent the geological maximum for tsunamis, often caused by massive landslides or asteroid impacts. One such prehistoric event is the Storegga Slide, which occurred around 8,100 years ago off the coast of Norway.
This massive submarine landslide involved the collapse of an estimated 3,500 cubic kilometers of sediment from the continental shelf, which plunged into the deep ocean. This enormous displacement generated a paleotsunami that swept across the North Atlantic. Scientists have found sediment deposits suggesting the waves reached heights of 20 to 25 meters (65 to 80 feet) in areas like the Shetland Islands and up to 10 to 12 meters along the Norwegian coast.
The largest tsunami event in Earth’s history was likely the one generated by the Chicxulub asteroid impact 66 million years ago. The impact of the 10-kilometer-wide asteroid into the shallow ocean near the Yucatán Peninsula created a megatsunami with energy estimated to be 30,000 times greater than the 2004 Indian Ocean Tsunami. Initial models suggest the immediate wave may have reached heights of up to 1.5 kilometers (nearly one mile) near the impact site. Geological evidence of this colossal wave exists in the form of massive “megaripples” engraved in deep-sea sediments.