Geology of the Badlands
Geology is the study of the earth. The Badlands let us see ancient layers of the earth without having to dig or make computer models. You can walk into Theodore Roosevelt National Park and see rocks that were created millions of years ago! These rocks are visible because of two things: weathering and erosion.
If you learn geology, you have to know these two words! Weathering is when rocks break apart; erosion is when stuff starts to move! There are different types of each idea, but that is a basic definition.
About 65 million years ago (give or take a few million!), the place we call North Dakota was a warm, swampy ecosystem. It supported many fish and reptile species. To the west, the Rocky Mountains were forming. As volcanoes erupted their ash dumped into the swamps. Erosion from the mountains also filled up the wet places. This means some layers you see in the Badlands are actually old mountains!
These layers of ash, sand and mud are called sediments. When they are buried for a long time they squish together to form rocks. We call them sedimentary rocks. Sandstone, limestone, and shale are types of sedimentary rocks.