Sedimentary rocks
can teach you a lot about the environment.
Sedimentary rocks are created when rock particles interact with water. Sedimentary rocks are formed from the sediments on the bottom of bodies of water, such as lakes, streams and oceans. Sedimentary rocks from different environments have different characteristics. Sandstone is common in areas such as a beach. Siltstone and mudstone are usually found where the land was once covered by deep oceans. Studying and comparing sedimentary rock samples can help geologists understand how the environment has changed over millions of years. The texture, shape and sorting of particles in the stone identify the environment where the sedimentary rock formed.
Instructions
1. Examine the texture of the sedimentary rock using a magnifying glass. Describe the texture of the sedimentary rock with particles that can be easily seen with the naked eye as "coarse," meaning it is composed of large pebbles (up to 2 mm) and sand. Describe a rock as "medium" texture if it contains small pebbles larger than 1/16 mm. Describe the sedimentary rock as "fine" if the particles consist almost entirely of tiny sand grains.
2. Use the magnifying glass to closely examine the shape of the pebbles and particles that form the sedimentary rock. Describe the particles as "rounded" (meaning they have no clearly defined edges) or "angular" (meaning the particles have defined corners). Categorize rounded particles as having been exposed to flowing water longer than rocks with angular particles.
3. Observe how the particles in the rock are sorted. Describe the sedimentary rock as poorly sorted if it contains a variety of different sized grains. Define a rock as well-sorted if the grains are similar in size. Break the rock with a hammer to examine layers within the rock.
Tags: sedimentary rock, Sedimentary rocks, Describe sedimentary, Describe sedimentary rock, magnifying glass
