Why Do Volcanoes Erupt?

Volcanoes are one of the most dramatic forces in nature. They can send lava flowing across the ground, fill the sky with ash and even create new land.

 

But why do volcanoes erupt? And what is going on beneath our feet when they do?

 

Let’s find out.

An eruption at Mayon Volcano, one of the most active volcanoes in the Philippines, shows just how powerful a volcano can be.

 

 

🌋 What is a volcano?

 

A volcano is an opening in Earth’s surface where hot rock, gases and ash can escape from below.

 

Hot melted rock beneath the ground is called magma. When magma reaches the surface, it is called lava.

 

Many volcanoes look like mountains because layers of lava and other material have built up during eruptions over thousands of years.

 

 

 

🌍 What’s happening beneath Earth’s surface?

Earth’s surface is made up of enormous pieces called tectonic plates. These plates move very slowly.

 

Many volcanoes are found around the edges of tectonic plates. As the plates move, magma from deep inside Earth can sometimes find a way towards the surface.

 

 

🔥 What about hotspots?

Not all volcanoes are found near the edges of tectonic plates. Some form above particularly hot areas deep beneath Earth called hotspots. Magma rises towards the surface here and can create volcanoes.

 

Hawaii is a famous example — its volcanoes formed above a hotspot in the middle of the Pacific Plate.

 

 

💥 Why do volcanoes erupt?

As magma rises towards the surface, gases inside it expand.

 

Sometimes the magma and gases become trapped beneath the ground and pressure begins to build. Eventually, they can force their way through cracks in the rock and escape through a volcano. An eruption has begun!

 

Some volcanoes erupt regularly, while others can remain quiet for hundreds or even thousands of years.

 

Watch a volcano erupt
Take a look at this incredible footage of an eruption in Iceland.

 

 

🌋 Are all eruptions the same?

No! Volcanic eruptions can look very different.

 

Some produce rivers of glowing lava that move across the landscape. Others are much more explosive and can blast ash, rock and gases high into the sky. The type of magma inside a volcano helps determine what kind of eruption takes place.

 

 

🌎 Famous volcanoes around the world

Mount Vesuvius, Italy

Mount Vesuvius is one of the world's most famous volcanoes. In AD 79, a huge eruption buried the Roman towns of Pompeii and Herculaneum.

 

🔎 Take a closer look: Can you find photographs of Pompeii and Mount Vesuvius online? What evidence of the eruption can you still see today?

 

Mount St Helens, USA

Mount St Helens erupted dramatically in 1980. Part of the mountain collapsed during the eruption and the surrounding landscape was transformed.

 

 

Mauna Loa, Hawaii

Mauna Loa is one of the largest active volcanoes on Earth. It rises more than 4,000 metres above sea level — but much more of the volcano lies beneath the ocean.

 

🔎 Take a closer look: Search for photographs or footage of Mauna Loa erupting. What do you notice about the way the lava moves?

 

Eyjafjallajökull, Iceland

When Eyjafjallajökull erupted in 2010, ash from the volcano travelled high into the atmosphere. Flights across the UK and Europe were cancelled because volcanic ash can be dangerous for aircraft.

 

 

Cotopaxi, Ecuador

Did you spot the volcano in our header image? It’s Mount Cotopaxi in Ecuador, one of the world’s highest active volcanoes. Its snow-covered peak rises to almost 5,900 metres above sea level.

 

 

🏴󠁧󠁢󠁳󠁣󠁴󠁿 Does Scotland have volcanoes?

Not active ones — but Scotland has a very volcanic past!

 

Millions of years ago, intense eruptions shaped much of the Scottish landscape. Some of the UK's most famous landmarks are actually extinct volcanoes:

 

• Arthur’s Seat & Castle Rock (Edinburgh): Part of an ancient volcano and its hard magma plug that erupted around 340 million years ago.
• Ben Nevis: The UK's highest mountain is the collapsed core (caldera) of an ancient super-volcano.
• Fingal’s Cave (Isle of Staffa): Famous for its hexagonal rock columns, formed by massive cooling lava flows.

 

The remarkable basalt columns of Fingal’s Cave are a reminder of Scotland’s volcanic past.

 

 

⚠️ How do people stay safe?

Scientists keep a close watch on active volcanoes.

 

They look for warning signs such as small earthquakes, changes in gases coming from the volcano and movement in the ground.

 

These signs can sometimes show that magma is moving beneath the surface. If an eruption looks possible, people living nearby may be warned to leave the area and move somewhere safer.

 

🎥 Watch: What warning signs can tell scientists that a volcano might be about to erupt? Discover three things they look out for.

 

 

💡 Did you know?

🌋 Most volcanic activity on Earth happens beneath the oceans.

🌋 The Ring of Fire around the Pacific Ocean contains hundreds of volcanoes.

🌋 Volcanoes can create brand-new land when lava cools and becomes solid rock.

🌋 Volcanic soil can be extremely fertile, making areas around some volcanoes excellent for farming.

🌋 There are volcanoes on other planets and moons. Olympus Mons on Mars is the largest known volcano in our Solar System.

🌋 A volcano that has not erupted for a very long time isn't necessarily extinct — it may simply be dormant.

 

 

🔎 Explore further: The island that appeared from the sea

In November 1963, fishermen off the coast of Iceland spotted smoke rising from the sea. It wasn't a ship on fire — an underwater volcano was erupting.

 

The eruption continued for several years and eventually created a completely new island: Surtsey.

 

See what you can discover about this extraordinary island.

• How did Surtsey get its name?
• How large did the island become?
• Why aren't most people allowed to visit it?
• What happened when plants and animals began to arrive?
• Is Surtsey still getting bigger today — or is something else happening to it?

 

Think about it: Surtsey gave scientists a rare opportunity to watch a brand-new island develop from the very beginning. What do you think they might have learned by studying it?

 

 

🫎 Keep exploring with Little Moose

Volcanoes are just one type of natural disaster that can have a huge effect on people and places.

 

Explore volcanoes, earthquakes, tsunamis and other natural hazards in our Natural Disasters — Second Level resource.

 

 

IMAGE CREDITS

Mayon Volcano - Darkimages08 / CC BY-SA 4.0 / Wikimedia Commons

Fingal's Cave on Staffa - Malcolm Neal /  CC BY-SA 2.0 /  Wikimedia Commons