This study aimed to determine the influence of the activities developed based on GEMS on students' conceptual understanding and scientific process skills on the subject of "Earth Crust". Mixed method, which includes the collective use of qualitative and quantitative research methods, was employed in this study. The study was carried out in a public village school located in the Eastern Black Sea Region of Turkey. The research sample consisted of the 4th grade students of this school. 13 students participated in the study. Data were collected by Scientific Process Skills Test, Conceptual Understanding Test, and semi-structured interviews. Six successive activities were conducted. These activities are as follows: Field Trip, Let's Examine the Rocks, Factors Influential on Soil Formation (Parental Involvement), Erosion, Fossils and Rocks with an Economic Value, and Mathematical Modeling. The research findings show that an improvement occurred in the understanding levels of the students regarding the concepts of rock, metal, fossil, soil formation, and erosion as a result of the activities conducted. In addition, they had an opportunity to make observations, collect, record, and analyze data. Moreover, the activities were supported by mathematical skills such as measuring, modeling, and creating graphs.