This paper studies Greek junior high school students' alternative ideas, both initial and synthetic, on geodynamic phenomena. It comments in detail on students' concepts on Earth structure, earthquake occurrence, volcano formation, and relief change. Additionally, it attempts to trace and interpret how and why these ideas form (concept development), presenting that initial and synthetic ones are indissolubly attached and utterly directed by environmental interaction. Data analysis verifies that curriculum inadequacy and false scientific terminology in textbooks enforce the generation of alternative ideas. New synthetic alternative ideas on geodynamic phenomena are presented which are mainly characterized by intermittent and fragmentary perspective. Furthermore, the characteristics of both initial and synthetic alternative ideas are outlined, giving emphasis on the facts that students represent geodynamic phenomena as instantaneous events and that they are able to describe the repeatability of the phenomena, but they show difficulty in capturing their continuity. Finally, more factors that control alternative idea development on geodynamic phenomena are highlighted--such as (i) lack of continuous thinking, (ii) distribution, intensity and frequency of geodynamic phenomena, and (iii) current affairs (i.e., pollution, technology evolution, human intervention)--hoping that their revelation will lead to alternative ideas' decomposition and thus to pure scientific knowledge.