Iconic Říp Hill was once a lava lake, researchers reveal
New research carried out by Czech scientists has revealed that Říp, the country’s most iconic hill, was once a lava lake. The solitary peak formed over 26 million years ago during a powerful volcanic eruption, which sent molten lava into a deep underground crater.
At just over 460 meters above sea level, Říp isn't the tallest mountain in the country—but its unmistakable shape makes it a dominant feature of the Central Bohemian Uplands, a volcanic landscape north of Prague.
This ancient hill also holds a special place in Czech mythology. According to legend, Forefather Čech climbed to the top of Říp, looked out over the land, and decided to settle there with his tribe. The story, thought to have taken place in the sixth century, was first recorded in writing by the chronicler Cosmas in the 12th century.
Now, scientists have looked even further back—millions of years—to uncover that beneath its quiet surface lies a story of fire, rock, and deep geological forces. While it was long known that Říp was of volcanic origin, until now, no one had studied its exact structure in detail, says geologist Filip Tomek, who led the research.
“Another interesting point is that this mountain stands alone—it is isolated from other volcanic complexes. If you go north, northwest, or west, you’ll find many volcanic hills and mountain landscapes in what’s known as the České středohoří Mountains and the Doupovské hory Volcanic Complex. In these two areas, there are tens—maybe even hundreds—of individual volcanoes, but they’re all clustered together. In contrast, Říp Hill stands completely apart.”
The study began with basic fieldwork. Armed with hammers, compasses, and cameras, the team hiked across the area, studying exposed rock. Most of this had to be done in autumn or winter when the vegetation thins out.
“We measured the structures and discovered a very interesting pattern of columnar joints. It’s a geological formation that develops as volcanic rock cools. But we weren’t certain about the exact origin, so we carried out additional analyses, including rock magnetism.
“That’s what led us to conclude that this must have been a lava lake—although we weren’t initially sure about the structure in which the lava solidified. In the end, we concluded that Říp Hill is actually the remnant of a so-called maar-diatreme volcano.”
This type of volcano begins its eruption underground. It happens when rising magma hits a water-saturated layer—like a massive steam cooker, explains Mr. Tomek:
“The steam increases pressure until it finally explodes below the surface, creating a deep depression known as a diatreme. On top of that, a crater forms, surrounded by an accumulation of volcanic debris. In our opinion, this depression was later filled with lava that intruded or ascended after that initial explosion.”
So what did the landscape around Říp look like when the Slavic forefathers arrived? Perhaps surprisingly, it looked much like today, says Mr. Tomek, although the hills were not as eroded.
“Many of the upper parts of volcanoes have eroded over time. Today, we see a lot of cone-shaped hills that look like volcanoes, but they’re remnants of magmatic dikes that once transported magma to the surface. These dikes are dense and more resistant to erosion, so they remain, while the actual volcanoes are mostly gone.”
While the study focused on geology, the project also involved two high-school students, whose role was to explore the connection between volcanoes and myth, says Mr. Tomek:
“Overall, we found something intriguing: in places with active volcanoes, myths don’t always include eruptions. It seems that if the local culture never witnessed an eruption, volcanism didn’t play a role in their stories.
"But with dormant or extinct volcanoes—like Říp—these isolated hills often become deeply mythical places. People admire them simply because they stand out in the landscape as lone, towering formations. And that, we believe, is what inspired legends like the one about the Czech forefathers.”
