Just as water recycles through evaporation, to rain and to ice, rocks are also recycled through time. Students have an intuitive sense of the water cycle, but have difficulty understanding how rocks change. This is probably because they don’t witness it to the same degree—after all, rocks change on a time scale that is difficult to comprehend.
Understanding and applying the concept of the rock cycle is essential in mastering basic geology and the effect on the environment.
Kathleen H. Robbins, an Earth Science and Astronomy teacher at Harry S. Truman High School in Bronx, NY, suggests teaching the rock cycle at the end of your Rock & Mineral unit. While some teachers prefer to lead with the rock cycle, Kathleen finds that students develop a better understanding when this is the capstone to the unit.
This lesson was originally created to teach the rock cycle as constructed for the New York State Regents Exam.
Download the Activity PDF
HOW ARE ALL ROCKS RELATED?
by Kathleen H. Robbins
Students will need to know:
- Sedimentary rocks form from the weathering, erosion and deposition of rocks that are then cemented and compacted into a new rock.
- Igneous rocks form from the cooling of melted rock, either intrusively from magma or extrusively from lava.
- Metamorphic rocks form from existing rocks being subjected to heat and/or pressure.
Through this activity, students will understand that there are certain properties common within rock types that will help identify them. Solid background reference materials and examples are needed as you teach the concepts and execute successful identification strategies.
Enduring Understandings
Students will understand that:
- All rocks can be weathered, eroded, deposited then compacted and cemented to form sedimentary rocks.
- All rocks can be melted and then cooled into igneous rocks.
- All rocks can metamorphose when subjected to heat and pressure.
Constructing the Rock Cycle
Construct the rock cycle from scratch, either on a white board or overhead projector, solely by eliciting responses from your students. This can be drawn for the class, but it is important that each student create their own. Color coding each rock type may be useful as well. There are a number of steps, but this exercise can move quickly as a Rock & Mineral unit review.
Q and A
- What are the 3 types of rock?
Students should be able to respond with Sedimentary, Igneous and Metamorphic.
Put these three words spaced inside blocks. - How do sedimentary rocks form?
Students should be able to respond with deposition and burial that cause compaction and cementation of rock fragments/sediments.
Place Sediments in an oval and draw an arrow from Sediments to the Sedimentary Rocks box. Label the arrow with “Compaction and Cementation” - How do sediments form?
Students should be able to respond with weathering and erosion.
Draw an arrow toward the Sediments oval and label it “Weathering and Erosion.” - Can sedimentary rocks weather, erode, be deposited then compacted and cemented?
Yes.
Draw an arrow from the Sedimentary Rocks box to connect to the Weathering and Erosion arrow. - Can igneous rock weather, erode, etc.? Can metamorphic?
Yes.
Draw arrows from the Igneous and Metamorphic rock boxes to the Weathering and Erosion arrow and label. - How do igneous rocks form?
Students should be able to respond with solidification of magma.
Place Magma in an oval and draw an arrow from Magma to the Igneous Rocks box. Label the arrow with “Solidification.” - How does magma form?
Students should be able to respond with melting of rocks.
Draw an arrow to Magma and label it “Melting.” - Can Igneous rocks melt?
Yes.
Draw an arrow from the Igneous Rocks box to connect to the Melting arrow. - Can Sedimentary rock melt? Can metamorphic?
Yes.
Draw arrows from the Sedimentary and Metamorphic rock boxes to the melting arrow and label. - How do metamorphic rocks form?
Students should be able to respond with change through heat/pressure. - Can Metamorphic rocks be subjected to heat and pressure?
Yes.
Draw an arrow from the Metamorphic Rocks box back upon itself. - Can Sedimentary rock be subjected to heat and pressure? Can igneous?
Yes.
Draw arrows from the Sedimentary and Igneous rock boxes to the Metamorphic box and label.
At this point, ask the students if they can teach the rock cycle to each other. As time allows (or as homework), have students write a story about a rock that goes through all three rock types and their formations.
Summary: Students should be able to realize that all rocks can become another type of rock.
