Waterfalls · Rainforest ValleyScience for kids

How does a waterfall form?

In short: A waterfall forms where a river flows over a steep drop or cliff and the water falls straight down. The falling water carries lots of energy, which turns into spray, a roaring sound and a deep pool carved at the bottom.

How it works

Many waterfalls form where hard rock sits on top of softer rock. The river wears away the soft rock faster, making a step. The step grows steeper and steeper, until the water no longer flows down a slope but drops right over the edge.

Water high up has stored energy. As it falls it speeds up, and when it crashes into the bottom that energy turns into flying spray, a roaring sound and churning waves. The higher the fall and the more water there is, the louder the roar and the further the mist drifts.

Year after year, the falling water digs a deep plunge pool and hollows out the soft rock underneath. Eventually the overhanging hard rock collapses. That's why many waterfalls slowly move back upstream over many, many years, leaving a gorge behind them.

Where to see it in New Zealand

New Zealand is full of waterfalls. Huka Falls near Taupō isn't tall, but the Waikato River squeezes through a narrow rocky channel there, so it's powerful and loud. In Fiordland, after heavy rain, countless temporary waterfalls pour down the cliffs of Milford Sound / Piopiotahi.

Try it together

Outside or in the bath, pour a cup of water into a bowl from just above it, then from a bit higher. Stay standing on the ground, with no climbing. Listen and watch: does water poured from higher make bigger splashes and a louder sound?

Kids also ask

What can the energy of falling water be used for?

People use falling water to spin turbines and make electricity, called hydroelectric power. A large share of New Zealand's electricity comes from hydro power stations on rivers and lakes.

Do waterfalls ever stop?

Some do. Temporary waterfalls that appear after heavy rain shrink and disappear once the weather clears, and in dry seasons some waterfalls dwindle to a thin trickle.

In the game, “Waterfalls” is a nature card on Rainforest Valley.

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 “Waterfalls” on the island ↗ All cards from Rainforest Valley