Volcano · Chimney VolcanoScience for kids

How does a volcano form?

In short: A volcano forms where magma from deep underground breaks through Earth's crust. Lava and ash pour out, cool and pile up around the opening, eruption after eruption, building a mountain. The pit at the top is the crater.

How it works

Deep inside, Earth is very hot, and in some places rock melts into thick, glowing magma. Magma is lighter than the solid rock around it, so it slowly rises, a bit like a bubble in water, and collects in an underground pool called a magma chamber.

Magma contains dissolved gas, like a shaken bottle of fizzy drink. When the pressure builds up enough, the magma forces its way through cracks to the surface. That's an eruption. Lava, ash and rocks land around the opening, then cool and harden.

Each eruption adds another layer. After many eruptions over thousands of years, the layers build a tall, cone-shaped mountain. The bowl-shaped pit around the opening at the top is the crater, and some craters fill with water to make a lake.

Where to see it in New Zealand

New Zealand has many volcanoes. Ruapehu, Tongariro and Ngāuruhoe stand in Tongariro National Park in the central North Island, and Taranaki Maunga / Mount Taranaki is a beautiful cone. In Auckland, Rangitoto Island was built by eruptions only a few hundred years ago.

Try it together

In a sandpit, make a small mound. Pour a cup of damp sand on top for an 'eruption', then sprinkle a thin layer of flour or crushed dry leaves as 'ash'. Repeat a few times, then use a spoon to dig into the side and look at the layers.

Kids also ask

What is a crater lake?

When a volcano is quiet, rain and melted snow can collect in its crater and form a lake. Mount Ruapehu has a crater lake near its summit.

Is Lake Taupō a volcano?

Yes. Lake Taupō fills a huge hollow called a caldera. Long ago, enormous eruptions emptied the magma underground, the ground collapsed into a giant pit, and water filled it.

Do volcanoes erupt without warning?

Most give signs first, such as small earthquakes, swelling ground or extra gas. New Zealand scientists watch the country's volcanoes closely so they can warn people when the danger is rising. But some small eruptions happen with little or no warning, so always follow the safety signs in volcanic areas.

In the game, “Volcano” is a nature card on Chimney Volcano.

Your child finds this card by reaching the right place or meeting the right weather on the island, and lights it up by answering the question on the back. Tap the button below and the game shows your child which island it is on and how to find it. Mochi Isle is a browser learning game for ages 5 to 18; the main island and the daily lesson are free.

Find “Volcano” on the island ↗ All cards from Chimney Volcano