Kanagawa Prefectural Museum of Natural History conducted a model experiment in which stratovolcanoes were created using coagulant waste food oil as lava and colored sand as pyroclastics. Participants were divided into groups. Each group made a volcano and then bisected the completed volcano and observed the cross sections. Participants drew two cross sections on provided worksheets: One was an imaginary drawing made before the experiment; the other was a sketch made after the experiment. 3,020 worksheets were collected. Several trends were found from analyses of the worksheets. The accuracy of the predicted profile of the stratovolcano depended on the area in which participants lived, rather than on their age. As for the predicted internal structure of the stratovolcano, while the proportion showing a horizontal-layer type was high in elementary school sixth graders, that of the textbook type was high among high school students. A correct predicted internal structure, called the “experimental type,” increased with age; and both the outline and internal structure became more accurate with age. A survey of elementary school students showed understanding increased in the sixth grade compared to the fifth grade and below. In particular, the understanding of the formation of strata showed the largest increase.