Here's why:

* Earth's Composition and Processes: Geochemistry studies the chemical composition of the Earth and the processes that govern its changes. This directly relates to geology, which studies the Earth's physical structure, history, and processes.

* Rock and Mineral Analysis: Geochemists analyze the chemical composition of rocks, minerals, and sediments. This analysis helps geologists understand the formation and evolution of rocks and minerals, the history of the Earth, and the distribution of resources.

* Geological Events and Processes: Geochemistry helps explain geological events like volcanism, tectonics, and the formation of ore deposits. This understanding helps geologists interpret geological maps, predict natural hazards, and explore for resources.

While geochemistry draws from other branches of earth science like physics, chemistry, and biology, its core foundation rests firmly within geology.