Rivers, mountains and volcanoes
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What you will learn
By the end, you can name the source, tributaries and mouth of a river and explain how mountains, volcanoes and earthquakes happen.
Explorer’s log: we followed the river upstream for three weeks. It grew narrower and faster, then it was a stream, then a trickle bubbling out of a mountain spring. Every raindrop that lands here has a journey ahead of it, all the way down to the sea.
Read the explanation
A river starts at its source, often a spring or melting snow in the hills, and flows downhill to its mouth at the sea. Smaller rivers that join it are tributaries. Earth’s outer shell, the crust, is cracked into huge plates that creep a few centimetres a year. Where plates push together, the land crumples into mountains. Where melted rock called magma rises through the crust, it builds a volcano. Where plates jolt past each other, the ground shakes: an earthquake.
- The Nile in Africa and the Amazon in South America are the two longest rivers on Earth; the Amazon carries by far the most water.
- Mount Everest, in the Himalayas, is the highest mountain above sea level, and the Himalayas are still slowly rising.
- Most volcanoes and earthquakes happen along plate edges, such as the Ring of Fire around the Pacific Ocean.