Isegoria

Last September, seismologists detected a monotonous hum emanating from Greenland — for nine days:

Soon after the vibrations began, a cruise ship sailing near fjords in Greenland noticed that on the remote Ella Island, a key landmark — a base used for scientific research and by the Danish military for sled dog patrols — had been destroyed.

[…]

The initial trigger came when warming temperatures caused the tongue of a thinning glacier to collapse, the researchers found. That destabilized a steep mountainside, sending a rock and ice avalanche crashing into Greenland’s deep Dickson Fjord. That displaced a massive volume of water, so a towering wave traveled across the narrow fjord, which is about 1.5 miles wide.

The tsunami waves — some at least as tall as the Statue of Liberty — ran up the steep rock walls lining the fjord. Because the landslide struck the waterway at a nearly 90-degree angle, waves bounced back and forth across it for nine days — a phenomenon scientists call a seiche.

[…]

The team determined that Ella Island — about 45 miles from the landslide — was battered by a tsunami at least 13 feet tall. Tourists sometimes visit the island.

“Just a couple of days before the event, cruise ships were there and they were on the beach,” Svennevig said. “It was really, really lucky that no one was there when it happened.”

This seiche was the longest scientists have ever observed. Previously, tsunamis caused by landslides typically created waves that died out within a few hours.

I hadn’t heard the term seiche before, and I wasn’t sure how to pronounce it. Was it Danish? Japanese? No, French — or Swiss-French:

A seiche (SAYSH) is a standing wave in an enclosed or partially enclosed body of water. Seiches and seiche-related phenomena have been observed on lakes, reservoirs, swimming pools, bays, harbors, caves, and seas. The key requirement for formation of a seiche is that the body of water be at least partially bounded, allowing the formation of the standing wave.

The term was promoted by the Swiss hydrologist François-Alphonse Forel in 1890, who was the first to make scientific observations of the effect in Lake Geneva. The word had apparently long been used in the region to describe oscillations in alpine lakes. According to Wilson (1972), this Swiss French dialect word comes from the Latin word siccus meaning “dry”, i.e., as the water recedes, the beach dries. The French word sec or sèche (dry) descends from the Latin.

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