Busting the "Man-Made" myth of Katla.
Because of its smooth, sculpted walls and the perfectly dark stripes of ash, many first-time visitors ask our guides: *"Is this cave man-made?"* The answer is a definitive **No**. Katla is a 100% natural phenomenon, carved by the raw power of Iceland's elements.
Every summer, the Mýrdalsjökull glacier melts on its surface. This water funnels into "moulins" (vertical shafts) and runs beneath the ice cap. These subglacial rivers are the architects, hollowing out the tunnels that we call ice caves.
The dark stripes aren't dirt or paint. They are layers of tephra (volcanic ash) from the Katla volcano's ancient eruptions. This ash settled on the glacier centuries ago and was buried by snow, becoming trapped within the glacial ice layers.
The smoothness of the walls is caused by the **venturi effect**—meltwater rushing through tight channels under extreme pressure, effectively "sandblasting" the ice with thousands of tiny particles of volcanic grit. This creates a finish that looks like polished obsidian or "Dragon Glass."
The ice you are touching in the Katla cave is estimated to be between 400 and 800 years old, having travelled from the center of the ice cap to the outlet glacier over centuries.
While the cave itself is natural, humans do provide two small assists for safety:
These minor modifications do not change the fact that the cathedral-like arches and the deep blue-black ice are masterpieces of nature.