what erupts from a volcano
A volcano is a vent or fissure in Earth's crust through which lava, ash, rock and gases erupt. A volcano is also a mountain formed by the accumulation of these eruptive products.Let's take a look at how volcanoes form: Earth's crust is 40 to 250 miles (64 to 402 kilometers) thick. volcano is a vent or fissure in Earth's crust through which lava, ash, rock and gases erupt. A volcano is also a mountain formed by the accumulation of these eruptive products. Let's take a look at how volcanoes form: