Our birding trip starts on Anegada, the northernmost island of the British Virgin Islands. Scientists are fascinated by its remote geological location and the legacy of calamitous catastrophes that molded it. Situated just south of the Puerto Rico Trench, where the Caribbean and North American tectonic plates converge, Anegada is particularly vulnerable to seismic activity. Recent studies conducted by K. Halimeda Kilbourne and her team have shed new light on a medieval tsunami that struck this region between 1381 and 1391, leaving behind coral boulders stranded hundreds of meters inland.
The research findings not only provide a historical account of past disasters but serve as a crucial warning for the Caribbean region, which continues to face significant coastal hazards. By employing uranium-series techniques on coral skeletons, researchers aim to gather valuable environmental data that may aid in predicting future events.
Geological Context of Anegada
While Anegada’s alluring geography makes it a unique paradise, it makes it susceptible to destructive risk factors. This is because the island towers above a very steep oceanic seafloor that drops off very sharply down to the abyssal Puerto Rico Trench. This unusual combination of topography makes it much more likely that a seismic event will result in flooding. Tectonic plates are colliding in the region, making major earthquakes possible with little or no warning. In addition, these quakes can generate massive and destructive tsunamis that endanger coastal communities.
The research team, led by Kilbourne, spent considerable time on Anegada to figure out what the island’s idiosyncratic geology means for how the island functions. These big coral boulders, pushed far inland by a previous tsunami thousands of years ago, act as important clues. They expose the island’s severe vulnerability to natural disasters of this magnitude. These titanic rock barricades serve as humbling markers of previously huge disasters. Beyond tourism, however, they serve an even greater purpose, and that’s for scientists studying seismic activity in the Caribbean.
Insights from Coral Skeletons
This is the primary method for determining the age of coral skeletons, which is one focus of Kilbourne’s research, measuring two radioactive elements—uranium and thorium. These elements, which break down at known rates, enable scientists to date the coral with precision. By studying these structures, Kilbourne and her team can get an unprecedented look at the conditions of the oceans’ past temperatures and salinity levels. This data is essential for reconstructing the in situ boundary conditions that existed at the time of major seismic events.
The coral skeletons that the medieval tsunami left behind can give scientists vital clues to what the history of tsunamis has been in the Caribbean. The research team’s findings indicate that Anegada’s steep seafloor slope played a critical role in how the tsunami impacted the island compared to other Caribbean locations. This difference highlights the importance of specific disaster readiness approaches for areas with comparable geological features.
Implications for Future Preparedness
The discoveries on Anegada have sweeping impacts for calamity readiness in the Caribbean. Researchers have focused in recent years on the possibility of similar catastrophic crises developing in the near future, particularly due to the region’s geological susceptibilities. Notably, Uri ten Brink, one of the project leads, urged researchers to investigate signs of similar geological activity that could affect Anegada and surrounding areas.
Computer simulations have demonstrated that a significant undersea earthquake in the adjacent Puerto Rico Trench almost certainly caused a tsunami. This third wave tsunami, ironically, led to the flooding of Anegada. These findings should lead decision makers in the continental US and British Virgin Islands to reconsider their coastal hazard risk evaluations. The study highlights the urgent need for improved tsunami preparedness and response strategies along the entire Atlantic seaboard.