How volcanoes build and change land — Earth science, 11–13 years
Follow magma from underground to lava at the surface, and see how eruptions can create land while also causing danger.
Magma becomes lava
Magma is hot melted rock beneath Earth’s surface. If it reaches the surface, it is called lava; gases and ash may escape with it. As lava cools, it becomes solid rock, so repeated eruptions can build cones, islands or broad layers of new ground.
Why do eruptions vary?
Volcanoes do not all erupt in the same way because magma differs in temperature, thickness and gas content. Runny magma lets gas escape and may produce flowing lava. Thick magma traps gas, allowing pressure to build and making explosive ash and rock more likely.
Building a volcanic cone
Imagine three eruptions each spread a 2-metre layer of lava around a vent. After the first, the ground is 2 metres higher; after the second, 4 metres; after the third, 6 metres. In reality, lava and ash may pile unevenly, so many layers build a sloping cone rather than a flat platform.
The volcano trap
It is easy to picture every volcano as a tall, smoking mountain because that is the familiar symbol. But some volcanoes are low and broad, and eruptions can happen through cracks or underwater. A volcano is defined by a route for magma to reach the surface, not by one particular shape.
Living near volcanoes
Volcanic regions can provide rich soils, geothermal energy and useful rocks, so people sometimes live near them. They also face lava, ash, poisonous gases, mudflows and fast-moving hot clouds. Hazard maps, monitoring and evacuation plans help communities use the benefits without pretending the danger is absent.
Keep exploring
Other languages
Loading MyLeoNes™…