Hornfels

Harry Hornfels is 300 million years old. The hornfels rocks belong to the group of metamorphic rocks.

Anyone can become like me! Because in my big family, we could originally have been any kind of rock! When conditions in the earth’s crust or on the earth’s surface change, with higher temperature or pressure, rocks can transform, and for example, become a hornfels. It doesn’t even have to get that much hotter-but I guess you would change a bit too if the temperature around you suddenly reached 500–600 degrees!

Before I became Harry Hornfels, I was part of Klara Limestone. I lay there completely still and relaxed, happy to be a nice, striped limestone. Then it just got so-o-o-o hot, I felt like I was being roasted! Apparently, there was a volcanic eruption right next to where I was lying! After that heat treatment, I was never quite the same again, I became harder, you know. But you can still recognize the stripes that remind you of Klara! Much later, a glacier managed to break me apart, even though I had become “tough as nails.” I was carried away by ice and water and ended up here. Geologists call me a metamorphic rock, and I guess that’s what I am! By the way, my family name means a rock as hard as horn or nails!

Facts

Hornfels belong to the group of metamorphic rocks. When the temperature increases-due to a lava flow or magma moving upwards in the earth’s crust-the heat can alter the surrounding rocks. Different starting points give different results. The limestone and claystone in the Grenland area were exposed to increased temperatures when there was active volcanism connected to the opening of the Oslo Rift. The hornfels that were formed usually still show the layering from the original rock.