Scientific discipline concerned with all aspects of volcanic phenomena. Volcanology deals with the formation, distribution, and classification of volcanoes, as well as their structure and the kinds of materials ejected during an eruption (e.g., lava, dust, ash, and gas). It also involves research on the relationships between volcanic eruptions and other large-scale geologic processes, such as mountain building and earthquakes. One of its chief aims is to determine the nature and causes of volcanic eruptions in order to predict them. Another practical concern is obtaining data that may aid in locating commercially valuable deposits of ores, particularly those of certain metallic sulfides.