This is the same as last year but you know - I never tire of geology. It is a good thing that I teach it and do research in it for a living!
Geology is the study of the Earth, from the center out to the outer atmosphere. It encompasses rocks and minerals, the hydrosphere (ocean, rivers, ice), and the atmosphere and the weather that takes place in it. It interfaces with biology as we study how the biosphere affects the soil and the atmosphere, and many other things. I've been told by astronomers that even the planets are considered the realm of planetary geologists, and astronomy begins beyond the Solar System.
I think my students are surprised that I spend only a week or two on rocks and minerals in the intro class, and we soon move on to plate tectonics, earthquakes, volcanoes, surface processes, the hydrosphere and the atmosphere.
I also find the natural world so beautiful: rocks, landscapes, seascapes, etc.