Step 1: Term Definitions.
(1) Phrenology: A false science using skull measurements to assess personality.
(2) Pedology: The science of soil in its natural setting. It studies soil creation, categorization, and mapping. This is the correct scientific term for soil study.
(3) Petrology: The geological study of rocks and their formation conditions. It focuses on rocks, not soil.
(4) Podology: An older term for Podiatry, which is the study and treatment of foot, ankle, and lower extremity disorders.
Conclusion: Pedology is the correct term for studying soil.