Analysis of Concepts about the Diversity of Igneous Rocks and Their Formation : Examples from Selected Earth Science Classes in Upper Secondary School

Abstract

We conducted research on concept formation concerning the diversity of igneous rocks and their formation among students in the second year of upper secondary school. Before and after the main three-hour classes (one hour on the classification of igneous rocks, one hour on crystallization differentiation, and one hour on the observation of rocks formed by crystallization differentiation), through concept mapping, we examined how the students got their concepts about the diversity of igneous rocks and their formation and how their concepts changed. After that, we showed a concept map made by one student to all of the students, who then revised their concept maps. As a result, it was revealed that before the three-hour classes, the students could not conceive of the relationship between minerals and igneous rocks, but after the three-hour classes they could grasp these concepts. After the students considered the concept map of one student and exchanged opinions, they developed more correct concepts about the formation of igneous rocks through crystallization differentiation. It seems that the students could understand the more precise structures of the concept of igneous rocks by recognizing how they were formed. However, before the three-hour classes (and even afterwards) most of the students didn't understand the concept that minerals were first crystallized from magma and then accumulated to form igneous rocks in a magma chamber. They thought that igneous rocks came from magma directly, and it seems that this resulted from the way in which "The Origin of Igneous Rocks" was taught in lower secondary school, so we suggest that the science curriculum include clear instruction that minerals are crystallized first and then form igneous rocks.