Become a backyard geologist—in one week

If you love recycling, you'll appreciate sedimentary rocks. They're built from bits of sediment created as water, ice, and wind erode even the mightiest mountain peaks, carrying the debris downhill. Sediment can also form from the crushed remnants of hard-shelled marine animals.   

Sedimentary rocks are like stenographers, excellent archivists of Earth’s history. By the sizes of their grains and styles of their layers, geologists can identify features from the past, like boggy swamps and catastrophic flood deposits, beaches and estuaries, great ocean depths, and rivers milky with pulverized rocks from glaciers. 

Sedimentary rocks also preserve fossils, plant pollen, and other traces of ancient climates, habitats, and life. 

Where they are found: Because they cover so much of Earth’s surface, sedimentary rocks are easy to find, especially between the Rocky Mountains and Appalachian Mountains. From Tennessee’s rolling Cumberland Plateau to the plains of eastern Colorado lie the remnants of ancient seas, rivers, and their floodplains, compacted into sedimentary rocks. 

Want to experience more wonder? National Geographic’s Wonder Listfeatures playful prompts and activities that turn everyday moments into wonder-filled discoveries—for families, anywhere, every day.