What is a volcano?
A volcano is a land or underwater feature that forms when magma reaches the surface of the earth it looks like a mountain that has a huge hole on top as you can see from the image below. Magma rises up to Earths surface because its density is less than rock. When magma reaches Earths surface it is now called lava. Volcanoes can cause the eruption of either gas, liquid, or solid materials. Hot gases, which is magma, and even solid rock can be explosively erupted from some of the Earths openings. Scientists study the composition of lava to better understand volcanic eruptions.