Deep beneath what is now western Germany, the ground shook and magma exploded upward, leaving behind perfect circular lakes that still dot the landscape today. Now, scientists have finally figured out when these dramatic eruptions stopped happening — and the answer is surprising.
The West Eifel Volcanic Field in Germany contains more than 100 maars, which are bowl-shaped lakes formed when underground explosions emptied magma chambers and groundwater rushed in to fill the void. These volcanic features were actually the first of their kind ever described by scientists, giving them their name. But for years, researchers could not pin down exactly when these eruptions occurred.
That changed thanks to a research team from Heidelberg University in Germany, Curtin University in Perth, Australia, and the University of Göttingen. They developed a clever new technique using tiny crystals called zircon, which contain radioactive elements that act like natural clocks. By measuring how much helium gas is trapped inside these crystals, the scientists could calculate when the crystals — and the volcanic rocks around them — cooled down during an eruption.
The results, published in the journal Contributions to Mineralogy and Petrology, reveal that the West Eifel volcanoes erupted in three major bursts: roughly 75,000 years ago, 48,000 years ago, and most recently about 25,000 years ago. The youngest and most intense episode happened during the coldest period of the last ice age, when ice sheets covered much of northern Europe. During this final phase, the famous Dauner Maare lakes and the Pulvermaar — a popular tourist destination today — were formed.
What surprised the researchers most was the pattern they discovered. Rather than erupting randomly over millions of years, the volcanoes tended to burst to life together across large portions of the region. "Our research also shows that, contrary to previous assumptions, continental volcanic fields are not subject to steady volcanic activity but can become active in short and sometimes very intense bursts," said Dr. Axel Schmitt, a scientist at Curtin University who worked on the study.
The findings also challenge an older theory that linked volcanic activity to warmer climate periods. Instead, the team's timeline shows eruptions coincided with dropping sea levels in the North Sea basin — the opposite of what scientists expected.
For people living near volcanic areas today, this research matters. Many continental volcanic fields around the world are home to large populations or popular tourism destinations. Understanding that these regions can experience sudden, intense bursts of activity — rather than gradual, predictable eruptions — could help communities better prepare for potential future volcanic events.