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The cycle of lava as a destructive and constructive force, building the structure of volcanoes and powering their devastating impact.Key facts
- Volcanoes are landforms that occur along plate boundaries.
- Volcanoes consist of a magma chamber, main and secondary vents and a crater.
- Volcanic eruptions occur when pressure forces magma from the chamber to the main vent.
- The pressure forces the crater to blow and release molten rock, ash and a cocktail of gases into the atmosphere.
Transcript
Volcanoes are our most explosive landforms.
Able to eject molten rock, and clouds of thick ash, high into the atmosphere with devastating consequences.
Volcanoes mostly occur along destructive and constructive plate boundaries, where plates are pushed together or dragged apart.
Destructive or constructive boundaries
Cracks or weaknesses allow magma to rise up from below the Earth's crust.
Pressure builds up, which then releases suddenly, causing the magma to explode – a volcanic eruption.
Magma that reaches the Earth's surface is called lava.
Lava
This molten lava eventually cools to form new rock.
After more eruptions over time, the mound of rock builds up, forming a cone-shaped volcano.
Volcanoes all have the same key structure.
A collection of magma underneath the volcano forms a hot, bubbling furnace, called the magma chamber.
Magma Chamber
The main vent allows this magma to escape.
Main Vent
And secondary vents are smaller outlets the magma can travel through.
Secondary Vents
The caved in surface is called the crater.
Crater
It's created after an eruption blows the top off the volcano.
Eruptions occur when pressure forces magma from the chamber, up the main vent, towards the crater.
If the ash and mud from a volcanic eruption mix with rainwater or snow, it creates fast-moving mudflows.
The hot lava and overwhelming mudflows can destroy huge areas.
However, volcanoes are also essential for life on our planet.
Scientists believe that volcanoes formed Earth's first atmosphere, by spewing water vapour, sulphur dioxide, nitrogen, and carbon dioxide into the air.
And volcanic eruptions continue to contribute to the carbon cycle – crucial to life – by releasing carbon dioxide.
They can go through long periods of being very active.
But they may also become dormant, not erupting for hundreds or thousands of years.
And eventually they can become extinct – just leaving a cone-shaped hill that never erupts again.
