by Mary Hoff
Big or small, sharp or round, each rock you see has a tale to tell about how the land around it has been shaped for millions or even billions of years. Just as detectives use clues to figure out how something happened, geologists use rocks to understand how natural forces change our planet. If you look and listen closely, rocks can tell you stories of oceans and volcanoes, great sheets of ice, and gushing rivers—all right here in what we now know as Minnesota.
Rocks are made up of minerals. Minerals are made up of molecules that line up in regular arrangements, called crystalline structure. How a rock looks depends on the kinds and amounts of minerals in it. A rock's size, shape, and location can give clues about what has happened to it over time.
Three rocks picked from the same field can have wildly different stories. One could have formed on an ancient shore when dinosaurs roamed the Earth. Another formed when Minnesota had volcanoes. A third rock formed miles underground under high temperatures and pressure from megatons of other rock. A glacier moving across the land more than 12,000 years ago carried all three rocks to this place.
Let's listen to the stories of a dozen of Minnesota's most famous rocks.
To read this entire Young Naturalists story, download the PDF below.