The Earth’s surface keeps changing
The surface of the Earth looks still, but it is always changing. Mountains, valleys, beaches and dunes are all landforms, and the forces of nature slowly reshape them. Running water carries soil and pebbles downhill. Waves wear down the coast. Wind lifts sand and piles it into dunes, as in Egypt’s Western Desert. Heat in the day and cold at night can crack rocks, and plant roots push into the cracks. Most changes are very slow and take a very long time. A few are quick, such as a flash flood or a landslide. Far away in Oman, Wadi Nakhr is a huge canyon with wavy cliffs and high peaks. Those shapes are clues that water, wind and a very long time carved it. A scientist looks at the clues in a landscape and asks questions.
| Force | What it does | Where you may see it |
|---|---|---|
| running water | carries soil and pebbles | a stream or the Nile |
| waves | wear down the coast | the sea at Alexandria |
| wind | lifts sand and builds dunes | the Western Desert |
| heat and cold | crack rocks | desert mountains |
| Change | Slow or quick? |
|---|---|
| crack widens | slow |
| flash flood | quick |
| pebble smoothed | slow |
| landslide | quick |
Clue walk. With a grown-up, walk round your school yard, street or park for ten minutes. Look for three clues that the land is changing: a crack with a plant growing in it, a worn step, a pile of sand or mud, a rut where water ran. Draw each clue and write whether the change is slow or quick, and what force caused it. Do not climb or touch anything unsafe.