Divers Have Just Spotted A Massive Coral Over 100 Feet Wide That May Be Older Than Ancient Civilizations

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Apr 4, 2026 - 14:00

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Divers Have Just Spotted A Massive Coral Over 100 Feet Wide That May Be Older Than Ancient Civilizations

A massive coral colony discovered in the remote Maug Islands has been identified as the largest Porites rus ever recorded. At a time when coral reefs face widespread decline, this formation stands out for both its scale and persistence.

Documented during the 2025 National Coral Reef Monitoring Program surveys, the coral was known locally but had never been formally measured. Its dimensions and estimated age now place it among the most remarkable reef structures observed in the Pacific. The discovery comes from a submerged volcanic caldera within the Mariana archipelago, an environment already recognized for its unusual chemical conditions.

A Coral of Exceptional Scale

The colony covers roughly 14,500 square feet (1,347 square meters), extending more than 100 feet (31 meters) across the top and reaching approximately 200 feet (62 meters) at its base. According to NOAA statement, this makes it the largest Porites coral ever reported. Its size posed immediate challenges. Thomas Oliver, a chief scientist with NOAA, explained that:

“This coral was so big, we actually couldn’t easily measure it due to dive safety restrictions,” which limited how far and how long researchers could explore the structure.

Its exceeds the dimensions of a similar formation documented in American Samoa in 2020 by a factor of about 3.4. Such a difference is notable, even within a genus known for producing large reef-building colonies.

Illustration Of The Measured Dimensions Of The Porites Rus Colony — _{Illustration of the measured dimensions of the Porites rus colony. Credit: NOAA Fisheries.}

Signs of an Ancient Organism Emerging

Estimating the coral’s age is less straightforward. Unlike some species,Porites rus does not produce clear growth bands, which are typically used to determine age in coral structures. As Hannah Barkley of NOAA’s monitoring program explained:

“It is difficult to tell the true age of this coral because it doesn’t produce growth bands like other corals,” she said, “We roughly estimate that Porites rus grows outward about a centimeter per year, so one could imagine that a colony of that size is pretty old.”

Scientists rely instead on average growth rates of about one centimeter per year. Based on that rate, a colony of this size could be more than 2,050 years old. It suggests the sea structure has survived centuries of change, but also shows the limits of current science, since its age can only be estimated, not precisely measured.

Top Down View Of The Coral Wall (left), With A Researcher Swimming Above Dome Shaped Formations At The Colony’s Summit (right). — _{Top-down view of the coral wall (left), with a researcher swimming above dome-shaped formations at the colony’s summit (right). Credit: NOAA Fisheries.}

Carbon Dioxide Built This Strange Ecosystem

The underwater colony’s habitat within the Maug caldera adds significant scientific interest. Often described as a “natural laboratory,” the site features carbon dioxide vents that create localized acidic conditions.

The national oceanic agency reported that these vents affect only small areas, leaving nearby zones where marine life can still thrive. Just a few hundred meters away, the massive reef grows outside the most impacted areas, highlighting how sharply conditions can vary over short distances.ommunities, linking scientific observation with local heritage.

The site lies within the Mariana Trench Marine National Monument, established in 2009 to protect unique ecosystems and support ongoing research. Efforts are also underway to give the marine formation a culturally appropriate name, with input from Chamorro and Carolinian communities.