Snow line · Cedar HighlandsScience for kids

What is the snow line, and why does its height change?

In short: The snow line is an invisible line on a mountain. Above it, it is so cold that snow lasts all year; below it, snow melts in summer. The nearer the equator, the warmer it is and the higher the snow line.

How it works

Every winter snow falls on the mountains, and every summer some of it melts. Low down, the summer sun melts it all. The higher you go, the colder it is and the less snow melts. At a certain height, more snow falls each year than melts, so it never all disappears. That boundary is the snow line.

Near the equator the sun is strong and the weather is hot, so you must climb very high before it is cold enough to keep snow, and the snow line is very high. Mount Kilimanjaro in Africa sits close to the equator yet has ice on its summit, though that ice is shrinking. Towards the poles the snow line drops, until in Antarctica snow and ice reach the sea.

Even on one mountain the snow line is not the same height everywhere. In the Southern Hemisphere, north-facing slopes get more sun, so snow melts faster and the snow line is higher. Shady slopes are colder and keep snow lower down, and so do slopes that get more snowfall.

Where to see it in New Zealand

On the highest parts of the Southern Alps / Kā Tiritiri o te Moana, such as Aoraki / Mount Cook, snow lasts all year and feeds glaciers like Franz Josef and Fox. When winter forecasts say 'snow to 500 metres', they mean how low that snowfall will reach, which is different from the permanent snow line.

Try it together

Put two ice cubes of the same size on two plates. Place one in the sun and one in the shade. Check every ten minutes: which melts first? Think about why the snow line is higher on the sunny side of a mountain.

Kids also ask

Does the snow line move?

Yes. In winter snow can cover the mountains much lower down, and in spring and summer the snow edge melts back uphill. The snow line usually means where snow survives at the end of summer. As the climate warms, many snow lines are rising.

What happens to the snow above the snow line?

It piles up year after year, and the weight squashes the lower layers into ice. When there is enough ice, it starts to flow slowly downhill as a glacier. So the area above the snow line is often where glaciers are born.

In the game, “Snow line” is a nature card on Cedar Highlands.

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 “Snow line” on the island ↗ All cards from Cedar Highlands