How volcanoes erupt — Earth science, 7–10 years
A volcano is an opening where hot melted rock and gases can escape from inside Earth. An eruption happens when pressure helps push this material upwards.
Magma, lava and ash
Melted rock below Earth’s surface is called magma. When it reaches the surface, it is called lava; broken rock and tiny glassy pieces can rise as ash. Gases trapped in the magma expand as it moves upwards, helping drive an eruption.
Why learn about eruptions?
People near volcanoes needed to understand why the ground could suddenly send out lava, ash and gases. Studying eruptions helps explain the signs before some eruptions and supports safer plans. It does not make every eruption predictable or harmless.
Following an eruption
Suppose a volcano sends lava 2 kilometres down a slope. Step 1: the lava leaves the opening as magma reaches the surface. Step 2: it cools from a glowing liquid into solid rock. Step 3: the new rock covers the ground along those 2 kilometres. Later eruptions can build another layer on top.
The reasonable mix-up
A common mistake is calling all melted rock lava, because lava is the word we hear most often. The useful difference is its place: magma is below the surface, while lava is magma that has come out. Once it cools, it becomes igneous rock, not liquid anymore.
Volcanoes in real life
Volcanic ash can affect flights, farms and breathing, while lava can damage roads and buildings. On the other hand, cooled volcanic rock can form new land and make some soils rich. Communities use maps, sensors and evacuation routes to reduce danger near active volcanoes.
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