Exploring the Rock Cycle
An understanding of the rock cycle is essential in geology and earth science classes.
By Lynsey Peterson
Looking at a rock, you wouldn’t think that it changes very much. Geological change is not easy for humans to observe because it happens over such a long period of time. However, it is important for students to understand rock cycle dynamics because rocks affect living things and even human society.
There are three types of rocks: igneous, metamorphic, and sedimentary. Igneous rocks are created when magma or lava cools, so they can be considered the parent rock of the other types. The size of the mineral crystals in an igneous rock depends on the speed of their cooling. Slower cooling creates the large crystals found in intrusive igneous rocks, while rapid cooling creates the small crystals of extrusive igneous rocks. When rocks are subjected to weathering and erosion, they are broken into sediments. These sediments can be deposited and compacted into sedimentary rock. If rocks are compacted greatly, creating heat and pressure, they can form metamorphic rocks. Of course, if enough heat or pressure is applied to the rock, it can melt to reform magma. That is why this is a cycle, though one that may take millions or billions of years. Even though we cannot directly show our students this process, we can help them understand the parts and processes of the rock cycle.
Taking students on a rock hunt is one way to engage them in the lesson. Keep your students together as a class as they survey the area around the school. When a student finds an interesting rock, place it in the class collection bag. You may also want to add various types of rocks to the class collection to avoid having a bag full of one type of rock. The students return to the classroom and work in small groups to identify the rocks. If your students have never used a dichotomous key before, you may want to help them with the first few specimens. Specific identifications are ideal, but it is also okay if your students at least identify the three major rock types.
Once students are engaged in the lesson through the inquiry-based activity, you can show them a diagram of the rock cycle and discuss the various ways that rocks are formed and reformed. Interactive animations of the rock cycle are easily found online and would be wonderful for students to explore using an interactive whiteboard or in the computer lab.
To avoid the common misconception that cycles proceed in one direction, I have my students use an game. I set up stations around the room with the various parts and processes of the rock cycle. At each station is a die and a list of the ways that rock can change at that station. Students start at any station and move around the room as the rolling of the dice indicates. They write down how the rock changes. After they have about twenty or so transformations, students return to their seats and either draw a comic strip or write a story about their rock cycle.
You can also extend your students’ understanding of the rock cycle with the lesson planning ideas below.
Rock Cycle Activities and Lessons:
In this lesson students learn about the rock cycle and how rocks change over time.
Using a variety of sites on the web, students learn about the rock cycle. They do hands-on activities to simulate the rock cycle and do research. They use the knowledge they have learned to write an essay about the rock cycle.
Students write and illustrate a book to show what they have learned after discussing the rock cycle.