Erosion: pieces on the move
After rock is weathered, its pieces do not always stay where they are. Erosion is the moving of these pieces from place to place. Gravity pulls rocks down mountainsides. Rivers carry soil and sand downstream, and muddy water is a sign. Waves drag sand along beaches. Rain washes soil down a farm slope. Wind carries sand: a gentle wind moves a grain about a metre at a time, and a stronger wind carries more sand farther. Glaciers are slow rivers of ice that carry rocks, but there are none in Egypt. Erosion can be quick, as in a flash flood, but most of the time we see only the evidence left by a very long time of it. The pieces that are moved are called sediment. Weathering breaks rock where it is, erosion moves the pieces, and the pieces settle later.
| What moves the pieces | Example |
|---|---|
| gravity | rocks roll down a mountainside |
| river | soil carried downstream |
| waves | sand dragged along a beach |
| rain | soil washed down a farm slope |
| wind | sand blown across a desert |
Draw the journey. In five boxes draw and label the journey of a pebble from a mountain top to the sea. Under each box write the force that moves it: gravity, rain, river or waves. Colour the box where weathering happened red and the boxes where erosion happened blue. Show it to someone at home.