Massive coral boulders litter the inland scrub of Anegada, a low-lying British Virgin Island.
These colonies weigh up to 10 tons and sit 1,200 feet from the sea.
They are geological anomalies that shouldn’t exist so far from the reef.
Geologists from the University of Maryland now believe these skeletons record a cataclysmic ‘ghost’ event from the 14th century.
Did this event happen without the wider world ever recording it?
A 1300s marine catastrophe: How giant coral skeletons ended up on a Caribbean island
Researchers first noticed the coral while surveying parts of the British Virgin Islands.
Many were massive reef corals broken from offshore environments and deposited far inland.
Some rested nearly 1,200 feet from where they originally grew beneath the ocean surface.
That distance immediately raised questions.
Standard storm surges lack the energy to transport 10-ton boulders 1,300 feet inland.
Computer models proved that even Category 5 hurricanes fail to replicate this displacement.
Researchers found ‘washover’ fans—thick layers of marine sand and shells—blanketing the island’s interior. These indicated a massive, high-velocity inundation.
That suggested seawater had crossed the island rapidly with unusual force.
Some coral pieces were simply too large for normal wave action to transport.
Forensics of a megatsunami: Reconstructing the event that erased a coastline
The island sits near the Puerto Rico Trench, the deepest part of the Atlantic, where the North American plate slides beneath the Caribbean plate.
Researchers began testing whether a major underwater earthquake could explain the deposits.
Computer simulations produced troubling results. Huge waves generated near the trench traveled directly toward Anegada.
This left the island’s geography unusually exposed.
Anegada lacks a protective continental shelf. Deep water reaches the shore, allowing tsunami waves to retain maximum kinetic energy until impact.
Powerful waves can approach the coastline with forceful momentum.
Precision radiocarbon dating of the coral’s internal growth rings narrowed the ‘time of death’ to between 1200 and 1450 AD.
Researchers sampled those layers to estimate when the corals stopped growing.
The timeline narrowed dramatically.
The data clusters around 1390 AD. No written records in the Americas exist for this period, making this a prehistoric ‘ghost’ disaster.
A major marine event likely struck the island during the medieval period.
Another clue strengthened that theory.
Sediment deposits inland matched patterns often left behind by tsunamis.
The water appeared to arrive suddenly, travel deep inland, and retreat violently.
The University of Maryland Center for Environmental Science realized they were no longer studying isolated coral fragments.
They were reconstructing an ancient coastal catastrophe.
That realization changed the direction of the study, “Stranged coral boulders point to a medieval tsunami in the Caribbean,” published in Science.
The coral skeletons may preserve evidence of a medieval megatsunami
Scientists now believe the coral was displaced by a massive tsunami triggered near the region.
A magnitude 8.0 or higher earthquake likely triggered a vertical displacement of the seafloor, launching a wall of water toward the Virgin Islands.
Computer models suggest the tsunami carried enough energy to rip coral colonies directly from offshore reefs.
The scale dwarfs the 1867 Virgin Islands tsunami. It suggests the region can produce ‘megatsunamis’ with heights exceeding 30 feet.
The coral skeletons became the evidence. A record of the planet’s history.
The sleeping giant: Why 35 million people are at risk
Anegada’s elevation averages only 6 feet above sea level. A repeat of the 1390 event would instantly submerge the entire island.
Over 35 million people in the Caribbean now live in high-risk inundation zones where tectonic pressure has been building for 600 years.
Tsunamis can arrive with almost no warning after underwater earthquakes.
This may be the clearest geological record of a Caribbean megatsunami ever identified.
For centuries, the evidence remained scattered quietly across the island.
But the powerful tectonic systems remain active today.
The 1390 disaster proves the Puerto Rico Trench is a ‘sleeping giant.’ Those 10-ton coral skeletons are the only surviving witnesses to a megatsunami that once erased the coastline
Powerful enough to reshape coastlines across the region without leaving written history.
We can no longer treat the 1390 megatsunami as a ghost of the past, but rather as a blueprint for a future we must urgently prepare for.