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The Last Tsunami to Strike the Virgin Islands Arrived 10 Minutes After the Earthquake

St. Thomas 𑁋 For decades, scientists have warned that the Caribbean Sea is geologically active. The Carribean Plate is a mostly oceanic tectonic plate underlying the Caribbean Sea and Central America and stretches as far as the northern coast of South America.

Danish West Indies Tsunami of 1867

A treasure trove of documents, first-hand accounts from locals and geological clues point to the Anegada Through, also known as the Virgin Islands Trough as the epicenter of a major earthquake that generated two tsunami waves in 1867. 

The Virgin Islands Trough is located between St. Thomas and St. Croix.

Documents and personal accounts from 1867 stored in archives located in Denmark and in the U.S. Virgin Islands’ Division of Libraries, Museums, and Archives detail a powerful quake that rocked the islands for several minutes. 

Once the shaking passed, eyewitnesses observed the water recede and rapidly return to the shore. The first of two waves struck the southern shore of St. Thomas — just 10 minutes after the earthquake was felt and pushed a large naval vessel onto the northern shore of St. Croix and wreaked havoc on its coastline.

In the Danish West Indies, now the U.S Virgin Islands, about 30 people died, with many of the fatalities occurring on ships or on the shore.

Growing Regional Threat

According to National Geographic, almost 75 percent of earthquakes occur along tectonic boundaries and the Caribbean plate is no exception. There are 19 known active volcanoes in the Eastern Caribbean.

Similar to the powerful earthquake that struck Honduras and prompted a tsunami warning for many islands in the Caribbean, a major earthquake that is generated in South America could have far-reaching impacts for the entire Caribbean archipelago.

To paint a better picture, if you drained all of the water between St. Thomas and St. Croix, it would reveal a striking mountain range-like terrain that exists below the channel. This explains why engineers have said over the years that a bridge connecting the two largest islands wouldn’t be practical — at least not utilizing bridge modern building standards. 

Tsunamis are Deadly Forces

Historical records show that some 3,500 people have died in the Caribbean by tsunami waves in the last 500 years — and in 2004, the Indian Ocean earthquake and tsunami killed approximately 227,000 people the day after Christmas. Making it the deadliest recorded tsunami in human history.

In 1692, an earthquake, tsunami, and liquefaction sank most of Jamaica’s pirate city, Port Royal. Liquefaction is a phenomenon in which the strength and stiffness of soil are reduced by earthquake shaking or other geological phenomena.

The 1867 tsunami that affected the then Danish West Indies caused deaths as far as Puerto Rico and Guadeloupe. Many Virgin Islanders assume (based on personal conversations compiled) that a tsunami will only impact a specific side of the island based on the angle of its approach — but that is not necessarily the case. 

Like hurricanes, every tsunami is different, and waves have been known to wrap around entire island chains upon impact, affecting the north, south, east and west shores of the landscape almost simultaneously. Hawaii fell victim to this in 1960 when a powerful earthquake generated in Chile sent tsunami waves across the Pacific Ocean — the waves traveled over 10,000 miles and killed people as far as Japan.

The shock is generally agreed to have had a magnitude of 9.5, though some studies alternately proposed that it may have been 9.4 or 9.6.

The ocean floor, the epicenter of the earthquake, mudslide or volcano, and the land the waves break on play a major role in how the destruction will unfold. Predicting the amount of destruction a region may face from a series of tsunami waves is not currently possible. 

Visualization of tsunami waves crossing the Pacific Ocean

“The potential for tsunamis is significant and has to be taken seriously,” says Christa von Hillebrandt-Andrade, who oversees the Puerto Rico-based Caribbean Tsunami Warning Program under the US National Weather Service. “Within the Caribbean and bordering the Caribbean, there are major fault structures and also volcanoes that could generate a tsunami at any time.”

A powerful earthquake could be potentially devastating to the U.S Virgin Islands and other Caribbean islands in the crosshairs of destructive waves. Unlike Puerto Rico, the Virgin Islands utilizes cisterns and collapsing structures could also see residents buried in the rubble as much as three stories high — structures that collapse into cisterns could create cases of drowning before rescue crews are able to remove the rubble.

Tsunamis can affect just about any coastal regions and can even be generated in lakes and other bodies of water if the right conditions are met.

The Virgin Islands Territorial Emergency Management Agency (VITEMA) this week conducted an earthquake drill on each island to prepare the public for these unpredictable natural disasters — this was perhaps VITEMA’s most important emergency drill in 2019.

In the event of a major earthquake, do not wait for sirens to blare on island — leave the coastline, abandon unnecessary valuables and head straight for the hills; as high as you can go.

Featured image courtesy of Vintage Virgin Islands