In the educational learning process preconceptions are an important factor. Learners usually interpret new input on the basis of their own preconceptions that are the result of various experiences made before being confronted with the educational learning process. Hence, the investigation of preconceptions is a main task for educational research. This study examines the preconceptions of thirteen grade 7 students (ages 12 and 13 years) on the topics "formation and location of deserts." Semi-structured and problem-centered interviews were used to collect the students' preconceptions. The following analysis was based on qualitative content analysis methods. Regarding the formation of deserts, four basic preconceptions were identified, e.g., "Wind amasses sand with the result that a desert forms." All four preconceptions have two characteristics in common: the origin of sand is simultaneously their basic concept and a problem of comprehension when thinking about the formation of a desert. Additionally, in the students' imagination all deserts are sand deserts. Concerning the location of deserts it can be stated that "heat" and "dryness" are the main factors, which are used when explaining the location. At the same time, the students seem to have no basic spatial grids and orientation systems concerning the location of deserts in the world that corresponds to scientific conceptions.