Drone photographer Jeroen Van Nieuwenhove flew over the fissure caused by the volcano in the early hours of 21 November, filming the lava flow, which, according to the Icelandic Meteorological Office (IMO), covered at least 7 square kilometres. The IMO has raised hazard levels, but activity has since reduced.

An eruption in January this year opened a 15-kilometre-long crack, into which magma flowed at the fastest rate ever recorded. In March, a plume of sulphur dioxide from another eruption in the area reached the UK.

A fossil site in Morocco has been called the “Pompeii of trilobites” as it contains sublimely detailed fossilised moulds of the creatures, preserved after a pyroclastic ash flow from a volcanic eruption around 509 million years ago.

“My jaw fell onto the desk,” says at the University of New England in Armidale, Australia. “I have never seen the level of detail preserved in these fossil trilobites. They are absolutely, no question, the best-preserved trilobites ever found.”

Trilobites are marine arthropods that existed from around 520 million years ago until nearly 252 million years ago. We know of more than 22,000 species and countless fossils have been discovered, but these are normally just their tough exoskeleton. The creatures’ soft parts are only found on rare occasions, and are always flattened and damaged.

However, the moment Paterson saw scans and images of trilobite fossils collected in 2022, from south-west of Marrakesh, in Morocco, he knew they were something special.

“On one of the more complete specimens, all of the appendages are preserved in 3D, right down to the bristles on their walking legs,” he says.

So far, Paterson and his colleagues have collected four specimens, each only around a centimetre long, representing two species from the Tatelt formation in Morocco. Two of the four trilobite specimens belong to the genus Protolenus, but the researchers are unsure whether they belong to a new species. The other specimens are Gigoutella mauretanica.

Pompeii is prized by archaeologists because ash from Mount Vesuvius quickly descended on the Roman city, preserving its structures and inhabitants. Once the ash cooled and formed into rock, each of the bodies decomposed, leaving a cavity that represents a perfect mould. The same thing happened to the trilobites, says Paterson.

The team scanned the moulds with a micro CT scanner and was able to create perfect 3D images of the creatures. “With these specimens, you can see anything you want at any angle,” says Paterson.

The scans have allowed the team to resolve some important details of trilobite anatomy that have been long debated, such as the structure of its feeding apparatus. For one of the individuals, it must have swallowed ash as it died because its digestive tract is filled with volcanic material and, hence, clearly preserved.

Another insight was how the creatures used their legs. “They have very gnarly-looking spines on the inner side of their legs,” says Paterson. “These would have acted like a shredding tool on whatever was their prey. In other words, they chewed with their legs and pushed the food from their legs up to their mouth.”

Iceland is bracing for a volcanic eruption, as thousands of small earthquakes have shaken the southern part of the Reykjanes peninsula since October. The earthquakes were caused by a huge amount of magma from deep inside Earth moving upwards and forming a 15-kilometre-long crack between 2 and 5 kilometres underground. As of 12.30pm GMT on 15 November, no volcanic eruption had begun.

In this part of Iceland, the volcanoes all seem to erupt around the same time every thousand years or so, in cycles called Reykjanes Fires, says Evgenia Ilyinskaya at the University of Leeds, UK. The last time this happened was around 800 years ago. “Now it’s pretty clear we are in this very active cycle again. We could be going into these kind of eruptions for the rest of our lifetimes,” she says. “Luckily, the eruptions that do happen in these [Reykjanes] Fires are all quite small.”

The huge eruption of Hunga Tonga-Hunga Haʻapai volcano last year triggered a powerful underwater volcanic flow that destroyed hundreds of kilometres of telecommunications cables and reshaped the seafloor.

The blast in Tonga was the most powerful eruption of the 21^st century, shooting ash 57 kilometres into the sky and causing 90-metre-high tsunami waves. “It was a really exceptional event,” says at the National Oceanography Centre in Southampton, UK.

The atmospheric impacts of the eruption were well documented. “But something really profound had happened on the seafloor and we didn’t know what it was,” says Clare.

Soon after the explosion, Clare and his colleagues decided to investigate the eruption’s impact on the bottom of the ocean.

Volcanic eruptions release a massive amount of material into the air, such as ash and lava. Some of this material quickly falls back down and forms what is known as a pyroclastic density current. “You’ll have seen loads of videos of it – imagine big clouds of really hot rock rolling down hillsides,” says team member , also at the National Oceanography Centre.

In the case of the Hunga Tonga-Hunga Haʻapai eruption, the material plunged straight into the ocean, producing a destructive underwater density current.

By mapping the locations of underwater telecommunication cables and when they were destroyed, the team calculated that the current must have travelled at 122 kilometres per hour.

The team also compared the map of the seafloor before and after the eruption and found that the density current travelled more than 100 kilometres across the bottom of the ocean, carving deep grooves along the way.

“This is the first time these underwater flows have ever been observed with modern technology,” says Clare. “The insights from the study have helped us to determine a hazard which wasn’t previously recognised as being potentially as big and significant as it is.”

Though it is hard to prevent the damage caused by volcanic eruptions, a better understanding of the resultant underwater density currents may help the telecommunications industry prepare for future events.

“The documentation of the impact of the Hunga-Tonga eruption to the seafloor geomorphology on the flanks of the volcano is a remarkable achievement,” says at the Monterey Bay Aquarium Research Institute in California. “The paper will likely be highlighted in geology textbooks for generations, both as it serves as a reminder of the scale of geologic hazards and as an end member [extreme example] of the types of sediment flows that occur on Earth.”

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