Sedimentary Rocks

Sedimentary rocks form when sediments are compacted and cemented together to form one mass of rock. Sediments are loose, unconsolidated rocks, organic matter, and other Earth materials found at the surface. Sediments are produced when rocks are weathered, or broken, into smaller pieces. Sediments can come in different sizes ranging from boulders to clay. Take a moment to view how sediments compare in the image on this page. As you can see, the largest sediments are boulder-sized and the smallest sediments are clay-sized. When a sedimentologist is analyzing a sedimentary rock, they always look at the size of the sediments that compose the rock.

Formation of a Sedimentary Rock

How does a sedimentary rock really form? Sedimentary rocks form by the processes of weathering, erosion, compaction, and cementation. Sedimentary rocks form in horizontal layers. View this presentation to investigate how sedimentary rocks form. Click the player button to begin.

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Classification of Sedimentary Rock

Even though there are different sediment sizes, sedimentary rocks are classified based on how they form. Sedimentary rocks are classified into three groups; clastic, organic (non-clastic), and chemical (non-clastic). In the interactivity, explore the different types of sedimentary rocks. Click the player button to begin.

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Sedimentary Rock Features

How a sedimentary rock forms can create distinct features in the resulting rock.  Sedimentary rocks have a few special features that help to identify them and also provide clues to the environment in which they formed. In this interactivity, click on each of the bars in the "accordion" to view sedimentary rock features. Click the player button to begin.

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Common Sedimentary Rocks

Now that you have learned how sedimentary rocks form, the types of sedimentary rocks, and the features of sedimentary rocks, it is time to investigate some examples. In the interactivity, you will learn more about each of the common sedimentary rocks. Click the player button to begin.

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Sedimentary Rocks Review

Now that you have explored sedimentary rocks, review your knowledge. In the non-graded activity, drag the descriptions on the right and drop them next to the correct vocabulary terms on the left. Click the player button to get started.