Explore the fundamental principles of geochemistry in this 30-minute lecture from the comprehensive 16-week Petrology course. Delve into the chemical composition and processes that shape the Earth's crust, mantle, and core. Learn about elemental distribution, isotope geochemistry, and the application of chemical principles to geological systems. Gain insights into how geochemistry influences rock formation, weathering, and the evolution of the Earth's surface. Designed for undergraduate and postgraduate geology students, this lecture by Dr. Harel Thomas, Professor of Applied Geology at Doctor Harisingh Gour Vishwavidyalaya, provides a solid foundation for understanding the chemical aspects of geological processes.