Hot molten rock spewing out of a volcano is called ______.

The term that describes hot molten rock that is expelled from a volcano during an eruption is "lava." When magma erupts to the Earth’s surface, it is referred to as lava. This distinction is important in geology because it reflects the location of the molten rock—magma is found beneath the surface, while lava is the term used for the same substance once it has reached the surface.

Understanding this terminology helps in grasping the processes of volcanism and the formation of landforms. Lava can flow, cool, and solidify into various types of volcanic rock, contributing to the landscape and geological formations that we observe. This distinction is crucial for students in geology or related fields, as it lays the foundation for understanding volcanic activity and the composition of the Earth’s crust.