It's impossible to pinpoint a single "first person" who discovered geology. The understanding of Earth's structure, processes, and history developed gradually over centuries, building upon the observations and theories of many individuals.

Here are some key figures and periods that contributed to the development of geology:

* Ancient Greeks: Philosophers like Aristotle and Strabo made observations about rocks, minerals, and landforms, though their interpretations were often based on philosophical rather than scientific principles.

* Renaissance Period: Leonardo da Vinci was a keen observer of nature and made important contributions to understanding fossils and geological processes.

* 17th and 18th Centuries: Scientists like Nicolaus Steno developed the fundamental principles of stratigraphy (the study of rock layers) and James Hutton proposed the theory of uniformitarianism, stating that geological processes operating today are the same as those that occurred in the past.

* 19th Century: Charles Lyell popularized Hutton's ideas, and William Smith created the first geological map, marking a significant leap in the development of the field.

Therefore, rather than a single "discoverer," geology emerged through the collective efforts of countless individuals across different eras, each building upon the knowledge of those who came before them.