lava

Lava is what molten (melted) rock is called when it flows out of a volcano or volcanic vent. Magma is what molten rock is called when it’s under the earth’s surface.

To be clear, in popular use, lava and magma are essentially different names for the same liquid-hot, charred orange ooze—which name is used depends on whether it is above or below the surface.

However, geologists and volcanologists have their reasons for using the two different terms to distinguish between forms of what is the same substance.

Magma doesn’t always become lava—sometimes it cools and solidifies beneath the earth’s surface. Sometimes, it collects in what’s known as a magma chamber. When it does reach the surface, it flows out as lava. The rock that’s formed when it hardens and cools can also be called lava, though this use of the term is uncommon outside of technical, scientific contexts.

The word lava is perhaps the more well-known of the two because that’s the one we see when volcanoes erupt (or when the floor turns into it).

Here is an example of lava and magma used correctly in the same sentence.

Example: Lava began flowing from the volcano three days after scientists detected movement of magma underground.

Want to learn more? Read the full breakdown of the difference between lava and magma.

Should lava or magma be used in the following sentence?

The eruption resulted in a steady flow of _____ from the volcano.