Geology topics are classified with the QE call numbers.
QE 1-350.62 | General Geology
QE 351-399.2 | Mineralogy
QE 420-499 | Petrology
QE 500-639.5 | Dynamic and Structural Geology (including volcanoes and earthquakes)
QE 640-699 | Stratigraphy
QE 701-760 | Paleontology
QE 760.8-899.2 | Paleozoology
QE 901-996.5 | Paleobotany
It might also be beneficial to browse other subjects with different call numbers of potential interest. These are broad ranges of topics but for more details, please check out PDF of the Library of Congress' guide to science call numbers.