Maka Lahi: The 1,200-ton boulder propelled inland by an ancient Tsunami

Located inland along the western shore of Tonga 's principal island, Tongatapu , is a giant enigma etched in stone. Locally called Maka Lahi , or " Tsunami Rock ," the enormous coral boulder is one of the world's largest of its type. Measuring approximately 15 meters long, 9 meters high, and weighing around 1,200 tons, the boulder looks preposterously out of place lying hundreds of meters inland, with no cliffs or steep ground in the vicinity that could have deposited it there.

How might such a massive piece of reef have been transported so far inland? The solution is not just remarkable, but also to be humbling: an ancient megatsunami .

The wave that moved mountains!
Geologists have concluded that Maka Lahi, along with many other similarly enormous boulders found in the surrounding area, was deposited there by a cataclysmic wave induced by an underwater landslide or volcanic eruption . These were no run-of-the-mill waves—scientists estimate them to have reached at least 35 meters as they crashed against the shoreline. The energy necessary to lift and transport a 1,200-tonne rock this far is beyond imagining, highlighting the savage strength of nature.

Unlike earthquakes or landslides, tsunamis have the ability to apply continuous pressure over a wider time span, permitting even the largest pieces of debris to be moved across flat ground. The reality that these boulders are composed of coral limestone , the same kind of reef material present offshore, ensures that they formed underwater before being forcibly tossed ashore.

A glimpse into the astonishing past
Radiocarbon dating of sediment near the rocks indicates that the tsunami hit during the 15th century, approximately 600 years ago. Coastal societies on Tongatapu would have suffered catastrophic loss and disruption at the time. In a few instances, geological events such as these are so uncommon and extreme that they affect not only landscapes but also entire cultures.

Interestingly enough, the memory of this ancient tsunami might still survive in oral traditions and generationally spread. Local legends tell of divine beings and otherworldly fights of giant birds and mighty gods throwing stones from the ocean. Mythological in character though these might be, these yarns might well be based on actual traumatic occurrences handed down as cautionary tales and cultural memory.

Now, Maka Lahi is a dramatic testament to just how volatile and powerful the Earth is. It's not a rock, really, it's a record of geology, a relic of culture, and a warning sign all wrapped into one. The boulder asks us to envision a day hundreds of years ago when the ocean became fierce and rewrote the topography in an instant.

As scientists continue to study it, Maka Lahi challenges us to better understand the world’s natural forces and to respect the stories scientific, legendary and astonishing, that help us make sense of them.