Scientists cracked the mystery of the last mega-earthquake in the Cascadia Subduction Zone, which stretches across British Columbia, Washington, and Oregon. They pieced it together by studying ancient trees, digging through geological clues, and listening to Indigenous oral histories. It turns out, a massive magnitude-9 earthquake slammed the region back in 1700, setting off a huge, destructive tsunami. The final piece of the puzzle came from old Japanese records describing an “orphan tsunami” — a tsunami with no local earthquake — that perfectly matched the timing. Thanks to all this evidence, scientists now know exactly what happened. And they’re warning everyone: the next “Big One” isn’t a maybe — it’s a guarantee.

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