The rocky material that is transported and DEPOSITED by rivers, seas, glaciers, and the wind is called sediment. Clay, sand, and gravel are all types of sediment. Sediments build up to form features such as mud banks along rivers or dunes in deserts. Sediments deposited on the seabed often build up over millions of years to form sedimentary rocks.


The laying down of sediments in water or on the ground is called deposition. Sediments are picked up by fast-flowing water, by strong, swirling winds, or by the ice in glaciers. Sediments are deposited when flowing water, wind, or glaciers cannot carry it any further – for example, when the water or wind slows down or stops, or when the glacier’s ice melts.


The shape of a sand dune depends on the strength and direction of the wind, how much sand there is, and whether plants grow on the dune or on the ground. Barchan (crescent-shaped) dunes form when the wind blows from one direction most of the time. They move forwards at up to 30 m (100 ft) a year as the wind blows sand over the crest.


A dune is a heap or hill made of sand or other small particles. Dunes are formed in sandy deserts and on coasts when loose, dry sand is picked by the wind and then deposited. In the Sahara Desert, North Africa, dunes grow up to 100 km (60 miles) long and 200 m (650 ft) high, forming an ever-changing landscape like giant ocean waves.

Copyright © 2007 Dorling Kindersley


Where Should Newborns Sleep?
We've rounded up all the alternatives and considerations to make a safe choice for your new addition.

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, and create reading lists for kids!

5 Tips to Help Make Your Child Self-Sufficient
Follow these tips to help your child become self-sufficient, and help him learn the skills he'll need to take care of himself.

Ready for Kindergarten?
Try our award-winning Kindergarten Readiness app! This easy-to-use checklist comes with games and activities to help your child build essential skills for kindergarten. Download the Kindergarten Readiness app today!

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Facebook icon Follow Us on Pinterest

editor’s picks