Mochi Isle
Volcanic ash · Chimney VolcanoScience for kidsHow can volcanic ash make soil fertile?
In short: Volcanic ash is made of tiny bits of rock and glass blasted out of a volcano. Fresh ash smothers plants, but it contains nutrients such as potassium, calcium and magnesium. As it slowly breaks down, the land becomes very fertile.
How it works
Volcanic ash isn't like the soft ash from a fire. It's made of tiny pieces of rock and volcanic glass, formed when magma is blasted apart in an eruption. It feels gritty and sharp and doesn't dissolve in water. Wind can carry it a long way before it settles, blanketing houses, trees and fields.
When it first falls, ash can snap branches, cover leaves so they can't catch sunlight, and spoil water supplies, so at first it's a disaster. While it's in the air it's dangerous too: it can harm people's lungs and damage aircraft engines.
But ash contains nutrients that plants need, such as potassium, calcium and magnesium. Over the following years, rain and plant roots slowly break it down and release them. Mixed with fallen leaves, it becomes loose soil that holds water and air well. That's why farms often thrive on the slopes of volcanoes.
Where to see it in New Zealand
Many parts of the North Island have soils that formed from volcanic ash. The plains around Taranaki Maunga are rich farmland dotted with dairy farms, and many Waikato pastures also grow on ash soils. When volcanoes such as Ruapehu erupt, ash can drift to towns a long way away.
Try it together
Fill one small cup with clean sand and another with garden soil. Plant a few bean or cress seeds in each, put them on the same windowsill and give them the same water. After a week or two, which cup is growing better? The nutrients in soil make the difference.
Kids also ask
Is volcanic ash the same as ash from a fire?
No. Fire ash is soft and light and crumbles easily. Volcanic ash is made of tiny, hard bits of rock and glass. Under a magnifying glass you can see their sharp edges.
How do people stay safe from ashfall?
Stay indoors with doors and windows shut. If you must go out, wear a mask and eye protection, and don't let children play in it. Wet ash is heavy and makes roads slippery.
In the game, “Volcanic ash” 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 “Volcanic ash” on the island ↗ All cards from Chimney Volcano