What is the term for magma that is erupted on the surface?

The term for magma that is erupted on the surface is "extrusive." This designation refers to magma that has reached the Earth's surface, where it cools and solidifies to form igneous rocks. This process typically occurs during volcanic eruptions. Factors such as the rate of cooling, the chemical composition of the magma, and the environment in which it erupts contribute to the characteristics of the resulting volcanic rock.

In contrast, the other terms represent different processes or formations related to magma. Intrusive refers to magma that cools and solidifies beneath the Earth's surface, leading to the formation of plutonic rocks. Sills and stocks are specific types of intrusive bodies that form when magma intrudes into pre-existing rock layers but do not reach the surface. Sills are often tabular and lie horizontally between layers, while stocks are larger, irregular bodies of intrusive igneous rock. Understanding these distinctions helps clarify the processes involved in the formation of different types of igneous rocks.