A tsunami is a series of powerful ocean waves caused by the displacement of a large volume of water, typically resulting from an underwater earthquake, volcanic eruption, or massive landslide. Since the Earth’s oceans and tectonic plates have always been in motion, tsunamis have been a natural phenomenon for billions of years, making the absolute “first” tsunami impossible to identify. To understand the history of these destructive waves, we must instead look at the oldest confirmed geological evidence and the earliest surviving human record of such an event.
The Science of Finding Ancient Tsunamis
Scientists rely on the field of paleoseismology to uncover evidence of tsunamis that occurred long before written history. This discipline involves searching for physical traces of ancient, high-energy wave inundations preserved in coastal environments like marshes, lagoons, and estuaries. These traces are most often found in layers of sediment known as tsunamites.
Tsunamites are distinct sedimentary layers, often composed of sand, mud, and sometimes boulders, deposited abruptly inland when a wave overwashes the coast. Researchers identify these layers by looking for sediment that is out of place, such as a sheet of marine sand interbedded within layers of peat or freshwater mud. Analysis is required to distinguish a tsunami deposit from one left by a severe storm surge.
Microscopic evidence provides further confirmation that the material was sourced from the deep ocean or near-shore marine environment. The presence of saltwater microfossils, such as fragmented marine diatoms, within sand found far inland is a clear sign of a powerful wave carrying material from the sea. Scientists then use techniques like radiocarbon dating on organic material within or directly above the deposit to determine the approximate age of the ancient event.
The Oldest Identified Prehistoric Event
The most widely documented prehistoric tsunami in the North Atlantic region is the one triggered by the Storegga Slide, which provides a clear geological marker for a massive, ancient coastal catastrophe. This event occurred around 8,200 years ago, between approximately 6225 and 6170 BCE, off the coast of Norway. The tsunami was not caused by an earthquake, but by a catastrophic submarine landslide on the edge of the Norwegian continental shelf.
An estimated 3,500 cubic kilometers of sediment slid down the slope and displaced the ocean water. The resulting tsunami crossed the North Sea, inundating coastlines across the North Atlantic basin. Evidence of this massive wave is preserved in sediment deposits across a wide area, including the coasts of the Faroe Islands, Iceland, and Great Britain.
In eastern Scotland, the wave left behind distinct sand layers in areas such as the Montrose Basin and the Firth of Forth. These deposits have been found as far as 29 kilometers inland and several meters above the modern sea level, confirming the immense scale of the inundation. The Storegga event is the oldest, most clearly defined prehistoric event in the relatively recent human epoch.
The Earliest Documented Historical Event
The earliest tsunami event that is robustly linked to both archaeological evidence and historical context is the one caused by the Minoan eruption of the Thera volcano. This catastrophic volcanic blast occurred on the island of Thera, now known as Santorini, in the Aegean Sea during the Late Bronze Age. Radiocarbon dating places the event in the mid-to-late 17th century BCE, or approximately 1600 BCE.
When the volcano erupted, the center of the island collapsed into the sea, forming a massive caldera and generating a colossal tsunami. The waves radiated outward across the Eastern Mediterranean, causing widespread destruction. Archaeological evidence of the tsunami’s impact is particularly strong on the island of Crete, which was the center of the Minoan civilization, located about 110 kilometers south of Thera.
Tsunami deposits, including marine sediments and pumice, have been found at coastal sites across the region, confirming the wave’s reach. Estimates suggest the wave may have reached heights between 35 and 150 meters near the source, with waves up to 9 meters high striking the coast of Crete. The widespread destruction from the eruption and subsequent tsunami is believed to have played a significant role in the eventual collapse of the Minoan maritime culture.