What are highlands, and how do cliffs form?

How it works

Think of highlands as a giant table standing above the land around it. Some are flat on top and some are bumpy. When the edge drops away steeply, almost like a wall, we call it a cliff. Cliffs often form in hard rock, because hard rock wears away slowly and can stay standing upright for a long time.

Sea cliffs are nibbled away by waves. The waves keep smashing into the bottom of the cliff and scoop out a notch. Without support, the rock above eventually breaks off and falls, and the cliff moves a little further inland. Rivers can also cut down into highlands, making deep, steep-sided gorges with cliffs on both sides.

High places feel cooler for two reasons. The sun mostly warms the ground first, and the ground then warms the air touching it. And as air rises, there is less air pressing down on it, so it spreads out, and air that spreads out cools down. That is why it usually gets cooler the higher you climb.

Where to see it in New Zealand

The Central Plateau in the middle of the North Island is a big area of highland, with the volcanoes Tongariro and Ruapehu standing on it, and it often gets snow in winter. At Cape Kidnappers in Hawke's Bay, tall sea cliffs are still being worn away by the waves.

Try it together

In a sandpit, build a steep little cliff out of damp sand. Pour water from a watering can against its base again and again, like waves. Watch whether the top collapses once the bottom is worn away. If you visit real cliffs, go with an adult and stay well back from the edge.