The catastrophic Indian Ocean tsunami of late 2004 claimed up to 300,000 lives in the space of 24 hours. In 2011, the Japanese tsunami claimed another 20,000 lives. Prior to these events, few scientists were interested in studying tsunamis as they believed that they were very rare events. An exception is Professor Ted Bryant of Wollongong University who has discovered that tsunamis regularly inundated the Pacific coast during Australia’s prehistory; the last event occurring in 1491.

The following summary is a selection of ancient tsunamis which have occurred during the era of human habitation and may have been responsible for millions of deaths around the world. All occurred during prehistoric times but left tsunami signatures of debris along coastlines.

The 6,000 BC Earthquake and Tsunami in the Mediterranean

In November 2006, scientists reported that a massive tsunami, triggered by a debris avalanche from Mount Etna in Sicily, ravaged the eastern Mediterranean about 8,000 years ago.

The Mount Etna avalanche sparked a tsunami. (Padda~commonswiki / CC BY-SA 2.5 )

The Mount Etna avalanche sent 6 cubic miles (25 cubic kilometers) of rock and sediment tumbling into the water at more than 200 miles per hour (322 kilometers per hour). Pummeling the seabed, it transformed thick layers of soft marine sediment into jelly, triggering an underwater mudslide. Researchers at the National Institute of Geophysics and Volcanoes in Italy used sonar equipped boats to survey the Ionian Sea floor sediment displaced by the avalanche.

They suggest that the tsunami reached heights of up to 165 feet (51 meters) in Sicily and Italy within 15 minutes of the avalanche. At speeds of 450 miles per hour (724 kilometers per hour), the tsunami would have swamped Greece and Libya with 43 foot (13 meter) high waves an hour later. After devastating the Greek islands and Turkey, the waves would have reached Egypt and Israel in just over three hours.

8,000 years ago, the shorelines of the Mediterranean were about 30 feet (10 meters) lower than at present, which compromises the identification of such tsunami deposits. However, a sunken Neolithic site, in Atlit-Yam, Israel, which was suddenly abandoned 8,000 years ago, has been identified as a possible victim of the tsunami.

Stone structure from Atlit-Yam, Israel submerged by tsunami. (Hanay / CC BY-SA 3.0 )

Any settlements on the coasts of southern Italy, Malta, Tunisia, western Greece, or Libya would have been completely annihilated by the towering waves . Many thousands of people must have been killed by this event which was even more catastrophic than the 2004 Indian Ocean tsunami.

The Santorini Tsunami that Destroyed the Minoans

About 1,600 BC the volcanic eruption of Thera in the Aegean caused massive tsunamis which inundated the Mediterranean and may have been instrumental in the demise of the Minoan culture . The exact date was not recorded in historical records, but scientists are able to study core samples and tree rings, while archeologists are able to date the Minoan settlement of Akrotiri on Santorini which was covered with feet (meters) of ash during the eruption.

Volcanic island in Santorini caldera. (Copyright Karen Mutton / Author Supplied)

Prior to the eruption on the existing island Nea Kameni, which was the center of the now mostly collapsed caldera, Thera was a much larger island. It is estimated that the Late Bronze Age eruption had a Volcanic Explosivity Index (VEI) of 6 or 7 which ejected the equivalent of 14 cubic miles (60 cubic kilometers) of rock and ash into the atmosphere.

Scientists believe that the eruption occurred over four phases. Intense eruption of magma and ash with up to 23 feet (7 meters) of pumice was deposited on the island. Towns like Akrotiri were buried. Pyroclastic flows and lava fountaining as well as tsunamis were generated. Initiation of the caldera collapse. Lava and lahar flows on Thera and collapse of caldera creating mega-tsunamis in the southern Mediterranean.

Crete, 62 miles (100 kilometers) from Thera, suffered from tsunamis reaching up to 92 feet (28 meters) in height during the final caldera collapse, with inundations reaching 1,476 feet (450 meters) inland in some areas. Archeological sites such as Amnissos, Pitsidia, and Palaikastro suffered damage from the volcano and tsunamis. Sedimentary deposits from the eruption have also been identified in southwest Turkey, the Cycaldes, Cyprus, Israel, and possibly in Sicily.

The settlement of Akrotiri, on the island of Thera, was buried in volcanic ash and pumice, which preserved many objects and artworks. First excavated by Spyridon Marinatos in 1967, Akrotiri appeared to be a ghost town when the volcano erupted, as no corpses have been discovered, indicating that the population had enough time to evacuate the island. Many historians, including Marinatos, believe that Thera was the original inspiration for Plato’s ‘ Atlantis’.

Akrotiri, Thera. (Copyright Karen Mutton / Author Supplied)

The North Atlantic Tsunami of 6,100 BC

In prehistoric times three huge landslides occurred underwater on the edge of Norway’s continental shelf, causing huge tsunamis in the North Atlantic Ocean. Known as the Storegga Slides ( Norwegian for Great Edge), three major underwater landslides caused a massive displacement of water.

The first occurred sometime around 30,000 to 50,000 years ago. The second and third occurred about 8,000 years ago when an area the size of Iceland slid into the Norwegian Sea. The dimensions were staggering - a 180 mile (290 kilometer) stretch of coastal shelf, with a total area of 840 cubic miles (3,500 cubic kilometers) caused a massive displacement of water which impacted the coast of Scotland, Norway, and the Shetlands.

In Norway, the coast shows evidence of a 33-66 feet (10-20 meter) tsunami. In Scotland, traces of the tsunami have been recorded, with deposited sediment being discovered in the Firth of Forth , 50 miles (80 kilometers) inland and 13 feet (4 meters) above normal tide levels.

Other parts of Britain show an inundation of about 8 feet (25 meters) above the high-water mark. In the Shetland Islands evidence for this event is widely displayed along peat cliffs and low-lying valleys. The major force of the tsunami was probably on the exposed headlands, but the greatest inundation was in inlets.

The Storegga Slide was first discovered in the late 1983 when Norwegian scientist Tom Bugge studied the underwater displacement and realized it had happened in three stages. In the 1980s, Professor Alastair Dawson of the Aberdeen Institute for Coastal Management noticed a ‘very curious’ layer of sand in the land along the Scottish east coast. Originally thought of as storm sediment, he became aware of the Norwegian scientists who had done a study on Storegga and realized that the sediments in Scotland were related to this ancient catastrophic event.

Storegga tsunami deposits (grey upper layer), bracketed by peat (dark brown layers), taken at Maryton on the Montrose Basin, Scotland. (Stozy10 / CC BY-SA 3.0 )

Indian Ocean Tsunamis

On November 14, 2006, the New York Times published an article called ‘ Ancient Crash Epic Wave ’ about a monstrous tsunami which struck the island of Madagascar circa 4,800 years ago. Huge wedge-shaped chevron deposits containing sediments from the ocean floor fused with a mixture of metals which are as deep as the Chrysler Building in Manhattan is high, and twice the area of Manhattan. These chevrons point in the direction of a newly discovered crater at the bottom of the Indian Ocean , 18 miles (29 kilometers) in diameter and 12,500 feet (3,810 meters) below the surface.

Burckle crater was discovered in 2005 by Dr. Dallas Abbott who estimates it to be between 4,500 to 5,000 years old. The obvious explanation is that a large comet or asteroid smashed into the Indian Ocean 4,800 years ago, producing a monster tsunami at least 600 feet (183 meters) high.

Location of Burckle Crater in the Indian Ocean. (Uwe Dedering / CC BY-SA 3.0 )

While many astronomers are skeptical that the chevrons were created by impact, scientists from the Holocene Impact Working Group are sure that a major impact occurs every millennium which can leave tell-tale signs in chevrons. Dr. Abbott uses satellite photography to scan the oceans for tell-tale signs of deep depressions, such as changes in the ocean surface which occur when either mountains or depressions are beneath the surface.

Dr. Abbott and her team have discovered chevrons in the Caribbean, Scotland, Vietnam, North Korea, and the North Sea as well as one on Long Island and another in Connecticut. With colleagues from the Novosibirsk Tsunami Laboratory in Russia, she visited the huge chevrons on Madagascar to study samples. They were found to contain tiny fossils from the ocean floor as well as iron, nickel, and chrome fused to the fossils which points to a chondritic meteor as the culprit.

Dr. Ted Bryant, a geomorphologist from the University of Wollongong, was one of the first scientists to recognize the signatures of mega-tsunamis. Such tsunamis leave deposits containing unusual rocks with marine oyster shells which cannot be explained by natural processes.

Speaking of the Madagascar tsunami, he commented, “No tsunami in the modern world could have made these features. Aceh was a dimple. End of the world movies do not capture the size of these waves. Submarine landslides can cause major tsunamis but they are localized. These are deposited along whole coastlines”.

Bruce Masse, an environmental archeologist at the Los Alamos National Laboratory believes that the comet fell on May 10, 2807 BC according to information contained in many flood myths from around the world, particularly those mentioning a full solar eclipse which occurred on that day.

Top image: Ancient tsunamis destroyed and killed. Source: Kevin Carden / Adobe Stock.

By Karen Mutton