One hundred and thirteen million years ago, the ocean's smallest builders fell silent — not from catastrophe above, but from acid rising within. Volcanic eruptions along the Kerguelen Plateau flooded the atmosphere with carbon dioxide, and the surface ocean, absorbing it first, turned hostile to the microscopic architects of the carbon cycle. A new study drawing on ancient shells from the Falkland Plateau reveals that this surface extinction was both more severe and more chemically distinct than any acidification event previously recorded — and that the deep ocean survived largely because the