Welcome Back Geologists! Sedimentary rocks 101

Sedimentary rock forms at or near the earth’s surface

Formation Processes that help form sedimentary rock include: weathering, erosion, deposition, compaction, & cementation

Weathering The process by which rock materials are broken down by the action of physical or chemical processes

Erosion The process by which wind, water, ice, or gravity transports soil and sediment from one location to another.

Deposition The process in which material is laid down or rock. Sediment settles out of water or wind carrying it during deposition.

Compaction The process by which sediments are pressed or squeezed together

Cementation The process in which sediments are glued or stick together after minerals crystallize

Arrangement of Sedimentary Rocks Strata Layers of rock

Clastic Chemical Organic Types of Sedimentary Rock

Made of fragments of rocks cemented (glued) together by a mineral Clastic Sedimentary Rock Made of fragments of rocks cemented (glued) together by a mineral

Conglomerate A type of clastic sedimentary rock Coarse-grained

Shale Another type of sedimentary rock Fine-grained

Chemical Sedimentary Rock Forms from solutions of dissolved minerals and water Example: Na + Cl = Halite

Organic Sedimentary Rock Forms from the remains of once-living plants and animals.

Examples of Organic Sedimentary Rock: Fossiliferous Limestone Coal

Sedimentary Rock Structures One noticeable feature of most sedimentary rocks is stratification. Stratification is the process in which sedimentary rocks are arranged in layers. Ripple marks, mud cracks, and rain drop impressions are all examples of sedimentary rock structures

Ripple Marks Shows the motion of wind and water waves on lakes, oceans, rivers, and sand dunes.

Mud Cracks Mud cracks form when sediments at the bottom of a shallow body of water are exposed to the air and then dry out.

Rain drop impressions When raindrops hit soft or fine-grained sediment, once the sediment dries you can see visible holes that are left behind (the raindrop impressions).

Uses of Sedimentary Rock Sandstone has been used as building materials because it is soft enough to cut easily into blocks or slabs. Limestone is used in making cement.

How much do you know? 1. what processes help form sedimentary rocks? 2. What does strata mean? 3. What are the three types of sedimentary rocks? 4. What are two examples of sedimentary rocks? 5. How can sedimentary rocks be used in the real world?

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