Part is rocks. Metamorphic, sedimentary, and igneous.
Part is plate tectonics.
Part's what's under the plates.
Phase transitions and magma composition.
Magnetic field formation.
All kinds of things.
But getting to the Bowden series in high school is a bit much, IMHO.
Earth sciences get pitched in with a lot of other stuff--from theories of the Earth's formation, the Moon's formation, origin of the atmosphere, and stuff before. And typically also gets teamed with meteorology, hydrology, ocean science, and so much more.
It's like physics. They teach classical mechanics (sort of) from speed through kinetic energy and momentum, but then thermal physics, electromagnetism, photoelectric effect and dribs and drabs of quantum-related "stuff", reflection/refraction and mirrors/lenses, waves and wave characteristics, circuits, electrostatics, and a lot of other details. It's a grab bag. It's far, far too much for one year if you want the kids to actually understand and retain much of it. Along the way they teach vectors, and since (at least in Texas) physics should be accessible to 9th graders, it's to be taught with a minimum of math. That "minimum" includes quadratic equations and more algebra than most 9th graders have.
It's an imperfect world. What should be taught, what is taught, what needs to be taught, and what can be taught are so completely different things as to make one want to crawl off and do something simple. Like teaching the kids to ID gneiss and feldspar.
= new reply since forum marked as read