The Roman Republic was faltering. Then a volcano erupted 6,000 miles away.

Sulfur is also indicative of a past rash. Sulfur dioxide, a gas commonly released by erupting volcanoes, reacts with water in the atmosphere to create sulfate aerosols. These tiny particles can linger in the stratosphere for years, riding wind currents, but they, like tephra, eventually fall back to Earth.

The ice also has a time stamp. Dr. McConnell and his colleagues are looking for variations in things like sodium, found in sea spray that is blown seasonally inland. By simply counting the annual changes in these elements, it is possible to trace the passage of time, said Dr. McConnell. “It’s like a tree ring record.”

Dr. McConnell and colleagues recently analyzed six ice cores drilled in the Arctic. In the layers of ice corresponding to the first months of 43 BC. The timing caught the attention of scientists.

Researchers have already hypothesized that an environmental trigger could have helped trigger crop failures, famines and social unrest in the Mediterranean region at that time. But so far, “There hasn’t been the kind of data these researchers have provided to really bring these theories into the mainstream,” said Jessica Clark, historian of the Roman Republic at Florida State University who was not involved in the research. .

Gill Plunkett, a paleoecologist at Queen’s University in Belfast, has launched an investigation. After extracting 35 pieces of tephra from the ice, she looked at the rock chemistry of probable volcanic suspects. Apoyeque of Nicaragua. Etna in Italy. Shiveluch from Russia.

But it was Okmok, a volcano in the Aleutian Islands of Alaska, that turned out to be the best match, at least on paper. To make the deal, two tephra samples – one from ice and one from Okmok – would have to be tested on the same instrument.

Dr Plunkett hosted a tephra presentation at a conference in Dublin. Alaska Volcano Observatory colleague Kristi Wallace packed four bags of Okmok tephra in her carry-on. The game was perfect, said Dr Plunkett. “There are events that are delicate. With Okmok, there is nothing else like him.

David C. Barham