What do the words volcanism and volcanoes indicate?
Volcanism includes the movement of molten rock (magma) onto or toward the earth's surface and also the formation of many intrusive and extrusive volcanic forms. It is induced in the lithosphere by energy due to geothermal gradients and heat flow from within the earth.
Volcanoes are associated with the process of volcanism and are discussed in relation to igneous rocks. They represent the volcanic forms created through the movement of magma onto or toward the earth's surface.
Explanation
The textbook context clearly defines volcanism as involving the movement of molten rock (magma) onto or toward the earth's surface and the formation of intrusive and extrusive volcanic forms. Volcanism is mentioned as being induced by geothermal gradients and heat flow from within. For volcanoes, the context references them in relation to Unit II and igneous rocks, connecting them to the volcanic forms mentioned under volcanism. This is a direct factual answer from the provided context.