The researchers studied how quartz-trachyte rocks change over time due to weathering. They looked at samples from two locations in Japan and found that as the rocks weathered, silica decreased in the lower layers but increased in the surface soil. Alumina and iron oxide increased in the lower layers but decreased in the surface soil. Calcium was more easily washed away than magnesium. The results suggest that iron oxide and certain clays moved from the upper layers to the subsoil. Overall, the study shows how different elements in the rocks change as they weather over time.