How to Date an Ancient Volcanic Eruption: Step 1, Use Fish Sauce

By Nina Bai | October 1, 2008 1:02 pm

garumAncient Romans loved their food smothered in a smelly, sweet and sour sauce, called garum, made from fermented fish. It was the ketchup of their time. Pompeii’s most famous garum maker, Aulus Umbricius Scaurus, was just starting a new batch when Mount Vesuvius blew its top and buried the city under hot ashes. Nearly 2000 years later, Italian researchers studying the site unearthed several jars of sauce-in-the-making and have used the contents to confirm the date of the deadly volcanic eruption.

The only eye-witness account of the eruption, a letter written by Pliny the Younger, puts the date at August 24, AD 79. This date is disputed because other artifacts, such as coins that seem to commemorate September events or fall produce sold at the market, suggest the eruption may have occurred as late as October.

But here’s the twist:

The fish sauce would not have been prepared in October. Garum was made from bogues (scientific name Boops boops), a fish that was abundant in the Mediterranean during the summer. Fish entrails were layered with herbs and salt and left out in the sun for 20 days. The garum jars found by the researchers were in the first stages of preparation.

The state of the fish sauce corroborates Pliny the Younger’s account of the late-August catastrophe. His description of the eruption was so detailed that vulcanologists now refer to that type of volcanic eruption—featuring a tall column of shooting gas—as Plinian eruptions. So you’d think he would’ve gotten the date right, too.

Image: Flickr/stu spivack

MORE ABOUT: Romans, volcanoes

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