In 1831, a volcano raised a new island from the Mediterranean; four powers rushed to claim it, but the sea erased it before anyone could win

For five months in the summer and fall of 1831, four nations eyed a smoking pile of rock in the middle of the Mediterranean Sea as if it were the last free parking space during Black Friday sales. The UK, France, Spain, and the Kingdom of the Two Sicilies all sent their boats. They all planted flags on that rock. And they all called it something different. Before the paperwork was even sorted, the sea took care of business. There was no treaty, no fight, no victor. Water did what it always does.

That makes for an amusing story, except that a 2021 study titled “The blue suns of 1831: was the eruption of Ferdinandea, near Sicily, one of the largest volcanic climate forcing events of the nineteenth century?” by a team of UCL volcanologists, published in the journal Climate of the Past, put forward the theory that this futile skirmish over some ash might have had serious repercussions for the climate of the Earth for years after the event, and may have been behind the "blue suns" reported in 1831, a theory that a more recent, more rigorous PNAS study in 2025 (posted online in December 2024) has since largely overturned.

One volcanic eruption, continent-wide disruption


It all started when seismic activity was experienced in the coastal city of Sciacca on the island of Sicily in the summer of 1831. The locals were accustomed to experiencing earthquakes because the geological nature of Sicily is indeed tempestuous, but this particular event did not stop there; some 30 miles from the shore, a submarine volcano known today as Empedocles began erupting under a depth of water of 150 meters. In July 1831, it had built an entire island for itself that was roughly 60 meters high and almost two kilometers in circumference. Everyone wanted it.

Four flags, one emerging island, many questions

The Brits were there first, at least on paper, with a Royal Navy captain naming it Graham Island after the First Lord of the Admiralty, Sir James Graham. Not surprisingly upset at having his coastline surveyed by a foreign navy, Ferdinand II of the Two Sicilies renamed the landmass "Ferdinandea." The French arrived next, with geologist Constant Prévost likening the eruption to uncorking a bottle of champagne, and naming it "Île Julia" for the month of its existence. Spain did not want to miss out on the drama either, making its own historical claims to the land.

For one brief shining moment, this was an actual diplomatic flashpoint, the kind of thing that would have had a real chance of turning into something more serious for empires that, quite frankly, delighted in escalating things. It was reported in the newspapers in all seriousness, with historical records indicating that members of French nobility were scouting the island as a potential vacation spot. Nobody, apparently, asked how stable the island was meant to be.

The scientist who showed up to actually take notes

It wasn’t built to last, and someone noticed it straightaway. Prévost, the French geologist, is the only one who is usually credited for doing science rather than just planting a flag at the place: he sketched the eruption, sampled some rocks, and correctly concluded that this island consisted of soft tephra, essentially volcanic gravel with the same stability of a sandcastle during the high tide. The waves from the Mediterranean Sea would quickly get rid of it.

Prévost was right. Nothing but a boiling, stinking column of water could be seen by ships in December 1831. When the diplomats started negotiations about the issue of sovereignty, nothing was left to argue about. Nature effectively invalidated the whole case. This geological instability persists even now. As it can be seen from the 2018 study titled “The Graham Bank (Sicily Channel, central Mediterranean Sea): Seafloor signatures of volcanic and tectonic controls,” published in Geomorphology, the place known today as Graham Bank is home to active seamounts, seeps and slopes that pose a danger, lying not deeper than nine meters underwater, which means the next eruption cannot be ruled out of the conversation.

Why a 19th-century squabble over nothing still matters

What’s interesting about all this is that the researchers found the eruption might have quietly wreaked havoc on Earth’s weather in ways not captured by other records. The UCL team discovered an unusual set of sightings in August 1831, ranging from Sicily to Virginia and China, where people saw blue, purple, and green suns. They concluded the sightings were linked to Ferdinandea, suggesting that the eruption may have somehow managed to send sulfate aerosols into the stratosphere.

That was the prevailing theory for some time. However, recent developments have complicated matters; for instance, the PNAS ice-core study, “The 1831 CE mystery eruption identified as Zavaritskii caldera, Simushir Island (Kurils),” using high-resolution sulfur-isotope analysis of ice cores, ruled out Ferdinandea as a meaningful source of the global sulfate signal, disproving the idea that it drove the 1831–1833 Northern Hemisphere cooling. The real culprit, the study found, was a previously overlooked, much larger eruption at the Zavaritskii caldera, an extremely remote volcano in Russia's Kuril Islands, which matches both the ice-core sulfur signature and the scale of cooling recorded at the time. The study doesn't fully rule out a smaller, localized role for Ferdinandea in the reported optical sky phenomena, but the claim that it drove global climate forcing has effectively been disproved.

This is also an all-too-common example of nineteenth-century imperialism: four nations rushed to hoist flags on unoccupied territory about fifty kilometers offshore without first considering whether it could withstand wave action. As recounted in a 1980 history-of-science paper “Graham Island, Charles Lyell, and the Craters of Elevation Controversy,” published in Isis, the incident became part of a legitimate scientific dispute of the time regarding the question of whether mountains were formed through a process of steady buildup or sudden elevation, with Graham Island serving as proof for both sides.

Nature, in this one instance, was quicker to resolve a colonial dispute than any international treaty, and did it with a nonchalant wave; and it turns out, we're still finding out exactly what else it was up to that summer.