Las Rocas Nos Cuentan Su Historia [Rocks Tell Their Stories]: Using Inquiry to Understand the Earth Processes That Form Rocks and Minerals
Llerandi-Roman, Pablo A., The Science Teacher
As a secondary school student, I grew interested in Earth science after observing marine fossils in the mountains and hearing popular stories of an ancient sea covering the spectacular karst belt in my hometown of Arecibo, Puerto Rico. Unfortunately, at the time, Earth science lessons focused on reading the text-book and memorizing rock and mineral names instead of using the rich geological context of the school to engage students in learning the concepts. The mogotes (hummocks), sumideros (sinkholes), and zanjones (trenches) of the karst belt (Monroe 1964; Lugo et al. 2001) were clearly far more interesting than the worksheets and textbook pictures of foreign sites shown in class.
Today, many Earth science lessons still focus on memorizing the names of rocks and minerals (Llerandi-Roman 2007). This led me to develop a lesson that reveals the fascinating stories told by rocks through the study of their physical properties. I first designed the lesson for Puerto Rican teachers, hence its Spanish title: "Las Rocas Nos Cuentan Su Historia." Through guided inquiry, students can discover the literal and figurative meaning of those words.
In this article, I explain how to implement and expand the lesson to address higher-level concepts. I also suggest teaching approaches that worked in my secondary and college classrooms. Finally, I share student worksheets in both English (Figure 1, p. 50) and Spanish (see "On the web"), which include key questions and instructions for the observation, description, measurement, and classification of rock and mineral samples.
Individual Samples Description and key characteristics Group of Samples Description and key characteristics Group Characteristics of subgroup 1 Characteristics of subgroup 2 Rock How did Where did the Key evidence type the samples form? samples (environments form? of formation)
Curricular sequence and application
During the first two weeks of classes, I implement a series of activities in my classroom that emphasize science process skills and the nature of science. For example, in one of these activities, students observe and describe a variety of objects, such as toys, books, and tools, placed on tables at the center of the classroom. They discuss what is required to make reliable observations and descriptions (e.g., the use of the senses, previous knowledge, spatial visualization skills). Then, students work with a series of activities in which they build physical models and test hypotheses related to how the models work. Finally, for the next two class periods, students usually work with a modified version of "Discovering Plate Boundaries" (Sawyer et al. 2005). These activities generate meaningful discussions related to the importance of collecting precise and accurate data and the empirical and tentative nature of science.
Las Rocas Nos Cuentan Su Historia, the last activity in this series, introduces Earth materials. The main objectives of this activity are to
* understand the physical characteristics of rocks and minerals,
* differentiate between rocks and minerals,
* identify different rock types, and
* develop basic understanding of the Earth processes that form rocks and minerals.
Planning, materials, and setup
To begin this activity, divide students into groups of two to four. Each group receives eight samples:
* one unidentified extrusive igneous rock,
* one intrusive igneous rock,
* one clastic (detrital) sedimentary rock,
* one chemical (nonclastic) sedimentary rock,
* one foliated metamorphic rock,
* one nonfoliated metamorphic rock, and
* two mineral samples (metallic and nonmetallic luster).
(Note: This exercise may work better by eliminating the chemical [nonclastic] sedimentary and nonfoliated metamorphic rock samples from the set of samples. …