Saturday, August 7, 2021

Disaster: Helike

 From Aeon Magazine:

Poseidon’s wrath
Vanished beneath the waves in 373 BCE, Helike is a byword for thinking about disaster, for ancients and moderns alike

One night nearly 2,500 years ago, the people of Helike, a city in the northern Peloponnese, were in their homes. Perhaps they were winding down with a glass of watered wine or already sleeping after spending the day about their business in the bustling town. Some had been busy at the market, selling or buying the produce from the local farms or purchasing goods from further afield. Some might have visited the famous Temple of Poseidon, as worshippers or priests of the cult, or trained in the gymnasium. Others were engaged in usual city business, the day-to-day civic and political life of Helike. This night, though, would be their last.

As they slept, a terrible earthquake struck the region, toppling buildings and killing the inhabitants. Then, in a second calamity, the city was swallowed up by a giant wave. The inhabitants disappeared. A recovery party of 2,000 men sent from neighbouring cities found no bodies. The nearby village of Bura was destroyed too.

The story of the destruction of classical Helike in 373 BCE rippled out through the Greek lands. When it was recent history, Aristotle (384-322 BCE) wrote of it in his Meterologica, a book not only about the atmosphere and weather, as we would expect, but also more generally about what we could term Earth processes, including earthquakes and tsunamis. Helike was remembered and written about for centuries by Greek and Roman authors. But as the centuries turned and the coastline shifted, the location of the once-great city was forgotten. The search for this city has captivated modern archaeologists for more than 50 years.

Exploring what happened at Helike involves looking at different types of evidence, including ancient texts, archaeological evidence and geological study. This search enables us to learn not only about this fatal disaster, bringing us closer to the people of the past, but it can also help reveal the way in which the ancient Greeks and Romans thought about how their world worked.

Greece is a common victim of earthquakes and tsunamis; it is the most seismically active part of Europe. In the past 10 years, there have been eight earthquakes of magnitude 6+. The Athens earthquake of 1999 killed 143 people (magnitude 6) and the 1953 Kefalonia earthquake killed 476 (magnitude 7.2). Since 1950, 22 earthquakes in Greece have also generated tsunamis. On 30 October 2020, there was a magnitude 7 earthquake and tsunamis struck the island of Samos and the Turkish coast. At Samos, the tsunami ran up onto the land to a height of 1.8 metres. In 1956, a tsunami hit the island of Amorgos, with a run-up height of up to 25 metres.

In the 20th century, our understanding of these phenomena is founded in a sure scientific basis through a century of geological work. Alfred Wegener’s theory of continental drift, proposed in 1912, led eventually to the development of the idea of plate tectonics, that the Earth’s surface was in motion, and then to its confirmation through observation and mapping of the ocean floors after the Second World War, especially the publication of the Tharp-Heezen map of the Atlantic in 1977. We know that earthquakes are caused by slipping and thrusting at faults, areas where the Earth’s tectonic plates meet. When this happens underwater, the motion causes the displacement of water, which results in tsunamis. Landslide, either above or underwater, is another mechanism that creates tsunamis and is a common result of earthquakes. The Amorgos tsunami was caused both by the displacement of the sea floor and by undersea landslides....

....MUCH MORE