Paleotsunami

A paleotsunami is an ancient tsunami, evidenced by modern technology. Some, such as the one resulting from the asteroid that wiped out the dinosaurs, were megatsunamis. It was over 1 mile (1.6 km) high and was a "global tsunami"; see also Cretaceous–Paleogene extinction event.[1]

For other uses, see Tsunami (disambiguation) and Tidal wave.
It is not possible to outrun a tsunami.

It is still an emerging science to identify and interpret paleotsunami deposits.[2] Not all paleotsunamis have no records, but all occurred long ago. Some, such as tsunamis resulting from the 1700 Cascadia earthquake left only oral traditions among the Native Americans of the Pacific Northwest. In North America, it left no written records, but it did lead to written records, in Japan.

Historical occurrences

Chile

On the coast of Chile, boulders have been found that "suggest directionality from sea to land," and they "could not be transported by rolling."[3]

On the northern Chilean coast, weighing more than 40 short tons (36 t), one boulder sits on the sand high above the Pacific, dwarfing every other rock in view in a conspicuous manner. Based on the effects of a tsunami that hit Japan, a tsunami 20 m (66 ft) probably hit the Chilean coast in 1420 AD, which swept boulders inland as if they were pebbles.[4]

In the sea off of the Atacama, on April 11, 1819, there was a magnitude 8.5 earthquake in the sea off Caldera. It lasted roughly 7 min and almost completely demolished the city of Copiapó. A tsunami with waves up to 4 metres (13 ft) high was registered. Within a radius of 800 kilometres (500 mi) it reached all coasts, making its way to Hawaii.[5]

See also 1420 Caldera earthquake, which generated tsunamis reaching Japan.[6]

Age determination of paleotsunami sediments around Lombok Island, Indonesia, and identification of their possible tsunamigenic earthquakes.

New Zealand

In New Zealand, boulders the size of cars have been found close to a 1 kilometre (0.62 mi) inland. No tsunami that large appears in historical records, but it may have happened around 1777 BC. It likely hit islands all across the South Pacific, including the Cook Islands, Tonga, and Vanuatu. Paleotsunami researchers do not yet know the full scale of the destruction the tsunami caused.[4]

China

A tsunami struck southern China and nearly wiped out civilization in what is now Guangdong. This was around 1076 AD, during the Song Dynasty, according to a study by Chinese scientists. On Lincoln Island of the Paracel chain in the South China Sea, large rocks and coral have been deposited on the island far away from the coast. The only explanation is a tsunami nearly 1000 years ago, and the earthquake was probably in the Manila Trench. The historical record was largely cut off after the tsunami, and major activity did not resume for centuries. The immense danger is that it could happen again.[7]

The Cascadia Subduction Zone

Off the coast of the American Northwest, the 1700 Cascadia earthquake generated a tsunami that was not quite a paleotsunami, as the tsunami was recorded, in Japan.[8] The Indigenous peoples of the Pacific Northwest Coast carried the story on in many oral traditions,[9] though they left no written records. There have been many paleotsunamis that hit the southwest coast of Canada, northwest coast of the United States through northern California.[10][11]

Eastern Mediterranean

In the Eastern Mediterranean, there is evidence of titanic paleotsunamis.[12]

Some historic paleotsunamis
Main article: List of tsunamis
YearLocationMain articlePrimary causeDescription
≈1.4 MaMolokai, HawaiiEast Molokai VolcanoLandslideOne-third of the East Molokai volcano collapsed into the Pacific Ocean, generating a tsunami with an estimated local height of 2,000 feet (610 m). The wave traveled as far as California and Mexico.[13][14][15]
≈9.91–9.29 kaDor, IsraelUnknownA mega-tsunami had a run of at least 16 metres (52 ft) and traveled between 1.5 and 3.5 km (0.9 and 2.2 mi) inland from the ancient Eastern Mediterranean coast.[16]
≈7000–6000 BCELisbon, PortugalUnknownA series of giant rocks and cobblestones have been found 14 metres (46 ft) above mean sea level near Guincho Beach.[17]
≈6225–6170 BCENorwegian SeaStoregga SlideLandslideThe Storegga Slides, 100 kilometres (62 mi) northwest of the coast of Møre in the Norwegian Sea, triggered a large tsunami in the North Atlantic Ocean. The collapse involved around 290 kilometres (180 mi) of coastal shelf, and a total volume of 3,500 km3 (840 cu mi) of debris.[18] Based on carbon dating of plant material in the sediment deposited by the tsunami, the latest incident occurred around 6225–6170 BC.[19][20] In Scotland, traces of the tsunami have been found in sediments from Montrose Basin, the Firth of Forth, up to 80 kilometres (50 mi) inland and 4 metres (13 ft) above current normal tide levels.
5,500 BPNorthern IslesGarth tsunamiUnknownThe tsunami may have been responsible for contemporary mass burials.[21]
≈1600 BCESantorini, GreeceMinoan eruptionVolcanic eruptionThe volcanic eruption in Santorini, Greece is supposed to have caused serious damage to the cities around it, most notably the Minoan civilization on Crete. A tsunami is supposed to be the factor that caused the most damage.

Current dangers

The possibility that a paleotsunami could occur is still present.

Scientists continue to find evidence of ancient tsunamis larger than those recorded in historical records.[22]

The Japanese 2011 Tōhoku earthquake and tsunami is a prime example of the dangers of ignoring evidence of past tsunamis. It was generated by a megathrust earthquake and made tsunamis up to 40 metres (130 ft) high. It washed over sea walls and drowned over 100 designated tsunami evacuation sites. Much of the problem was Japan's poor defenses. From historical records, there were three large tsunamis dating back as far as the 17th century, some producing waves dozens of meters high. However, the Japanese based many of their tsunami-defense preparations on smaller tsunamis that had previously hit Japan. In 2011, tsunamis destroyed entire cities, crippling the Fukushima Daiichi Nuclear Power Plant. Over 15,000 people were killed.[4] Not long before the Tōhoku earthquake, the Japanese had set up tsunami stones, warning of tsunami danger. One reads "High dwellings are the peace and harmony of our descendants. Remember the calamity of the great tsunamis. Do not build any homes below this point."[23][24]

Taiwan has evidence of paleotsunami events.[25] More research is needed.[26]

Megatsunami on other planets

The surface of Mars once had oceans but is now dry, and a 2019 study found a paleotsunami may have ravaged some of the surface after a cosmic impact similar to the one that created the Chicxulub crater and likely ended Earth's age of dinosaurs. The impact may have made Pohl Crater.[27] Near where Viking I landed were many boulders, possible debris from a megatsunami, which may have struck perhaps 3.4 billion years ago. The megatsunami could have reached 930 miles (1,500 km) from the impact site, well past Viking 1's landing site. The tsunami may have been 1,640 feet (500 m) high on the ocean, and perhaps 820 feet (250 m) on land.[28]

What happened was possible via two different scenarios, one caused by a 5.6 miles (9.0 km) asteroid meeting "strong ground resistance," releasing 13 million megatons of TNT energy, or a 1.8 miles (2.9 km) asteroid hitting the softer ground, releasing 0.5 million megatons of TNT energy.

For perspective, the most powerful nuclear bomb ever tested, Tsar Bomba, created 57 megatons of TNT energy.[29]

See also

References
  1. Bressan, David (March 11, 2021). "Century-Old 'Tsunami Stones' Saved Lives In The Tohoku Earthquake Of 2011". Forbes.
  2. "Tsunami Hazards, Modeling, and the Sedimentary Record". USGS. September 7, 2021.
  3. Carballeira, R.; Peña‑Monne, J. L.; Otero, X. L.; Sampietro‑Vattuone, M. M.; Castro‑Correa, C. P.; Soto‑Bauerle, M. V.; Pérez‑Alberti3, A. (2022). "Paleotsunami evidence in the Bahía Inglesa coast (Atacama, Chile) based on a multi‑approach analysis" (PDF). Environmental Earth Sciences (published February 24, 2022). 81 (5). doi:10.1007/s12665-022-10259-2. S2CID 244212989.
  4. Scharping, Nathaniel (February 16, 2023). "Chilean coast". Hakai Magazine.
  5. Carballeira1, R. (2022). "Paleotsunami evidence in the Bahía Inglesa coast (Atacama, Chile) based on a multi‑approach analysis" (PDF). Environmental Earth Sciences. 81 (5). doi:10.1007/s12665-022-10259-2. S2CID 244212989.
  6. Yoshinobu, Tsuji (2013). "Catalog of Distant Tsunamis Reaching Japan from Chile and Peru" (PDF). Report of Tsunami Engineering. Archived from the original (PDF) on March 20, 2020.
  7. Griffiths, James (January 3, 2019). "Ancient tsunami almost wiped out civilization in southern China, study finds". CNN.
  8. Schulz, Kathryn (July 13, 2015). "The Really Big One". The New Yorker.
  9. Steele, Bill (September 4, 2012). "Native American Stories expand history" (PDF). Archived from the original (PDF) on July 24, 2015.
  10. "Searching for Evidence of past Tsunamis in Sediment Cores". Pacific Coastal and Marine Science Center November 23, 2021. November 23, 2021.
  11. "Central Cascadia subsidence and paleotsunami events for the last ~2,500 years".
  12. "Evidence for a massive paleo-tsunami at ancient Tel Dor". ScienceDaily.
  13. "Hawaiian landslides have been catastrophic". mbari.org. Monterey Bay Aquarium Research Institute. October 22, 2015.
  14. Culliney, John L. (2006) Islands in a Far Sea: The Fate of Nature in Hawaii. Honolulu: University of Hawaii Press. p. 17.
  15. "Kalaupapa Settlement Boundary Study. Along North Shore to Halawa Valley, Molokai" (PDF). National Park Service. 2001. Retrieved June 29, 2020.
  16. Shtienberg, Gilad; Yasur-Landau, Assaf; Norris, Richard D.; Lazar, Michael; Rittenour, Tammy M.; Tamberino, Anthony; Gadol, Omri; Cantu, Katrina; Arkin-Shalev, Ehud; Ward, Steven N.; Levy, Thomas E. (December 23, 2020). "A Neolithic mega-tsunami event in the eastern Mediterranean: Prehistoric settlement vulnerability along the Carmel coast, Israel". PLOS ONE. 15 (12). e0243619. Bibcode:2020PLoSO..1543619S. doi:10.1371/journal.pone.0243619. ISSN 1932-6203. PMC 7757801. PMID 33362214.
  17. Baptista, M. A.; Miranda, J. M. (2009). "Revision of the Portuguese catalog of tsunamis" (PDF). Nat. Hazards Earth Syst. Sci. 9 (1): 25–42. Bibcode:2009NHESS...9...25B. doi:10.5194/nhess-9-25-2009. Archived (PDF) from the original on April 3, 2013. Retrieved September 30, 2012.
  18. Bondevik, Stein; Dawson, Sue; Dawson, Alastair; Lohne, Øystein (August 5, 2003). "Record-breaking Height for 8000-Year-Old Tsunami in the North Atlantic" (PDF). Eos, Transactions, American Geophysical Union. 84 (31): 289, 293. Bibcode:2003EOSTr..84..289B. doi:10.1029/2003EO310001. hdl:1956/729. Archived (PDF) from the original on August 7, 2011.
  19. Bondevik, S; Lovholt, F; Harbitz, C; Stormo, S; Skjerdal, G (2006). "The Storegga Slide Tsunami – Deposits, Run-up Heights and Radiocarbon Dating of the 8000-Year-Old Tsunami in the North Atlantic". American Geophysical Union meeting.
  20. Bondevik, S; Stormo, SK; Skjerdal, G (2012). "Green mosses date the Storegga tsunami to the chilliest decades of the 8.2 ka cold event". Quaternary Science Reviews. 45: 1–6. Bibcode:2012QSRv...45....1B. doi:10.1016/j.quascirev.2012.04.020.
  21. Cain, Genevieve; Goff, James; McFadgen, Bruce (June 1, 2019). "Prehistoric Coastal Mass Burials: Did Death Come in Waves?". Journal of Archaeological Method and Theory. 26 (2): 714–754. doi:10.1007/s10816-018-9386-y. ISSN 1573-7764.
  22. Scharping, Nathaniel (February 18, 2023). "Paleotsunamis Offer a Quiet Warning". The Atlantic.
  23. Lewis, Danny (August 31, 2015). "These Century-Old Stone "Tsunami Stones" Dot Japan's Coastline". Smithsonian.
  24. Bressan, David (March 11, 2021). "Century-Old 'Tsunami Stones' Saved Lives In The Tohoku Earthquake Of 2011". Forbes.
  25. Yoko, Ota (September 26, 2013). "Paleotsunami Study in Taiwan" (PDF).
  26. Yoko, Ota; Shyu, J. Bruce H.; Wang, Chung-Che; Chung, Ling-Ho; Shen, Chuan-Chou (2015). "Coral boulders along the coast of the Lanyu Island, offshore southeastern Taiwan, as potential paleotsunami records". Journal of Asian Earth Sciences. 114: 588–600. doi:10.1016/j.jseaes.2015.08.001.
  27. Zastrow, Mark (December 6, 2022). "Megatsunami swept over Mars after devastating asteroid strike". Astronomy.
  28. Ashley, Strickland (December 2, 2022). "NASA's Viking 1 may have landed at the site of an ancient Martian megatsunami". cnn.com.
  29. Ashley, Strickland (December 2, 2022). "NASA's Viking 1 may have landed at the site of an ancient Martian megatsunami". CNN.
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