RIVERS

Rivers drain the surrounding land, carrying water that falls as rain and snow down to the sea. As rivers flow, they erode (wear away) rock, breaking it into fragments, called sediments, that are carried downstream. Most erosion occurs when rivers flood after heavy rain or as mountain snows melt in spring. Over time, erosion creates valleys and waterfalls, and sediments form land areas called flood plains and deltas.

RIVER’S COURSE

A river has three main stages. In the first, the river is steep and narrow and its flow is rapid and rough. In the second stage, it is wider, less steep and flows more smoothly through flat-bottomed valleys. In the third stage, the river is broad and flows placidly across flat coastal plains to the sea, where it drops its sediment.

LIMESTONE CAVES

When water flows over some rocks, such as limestone, caves may be formed by a process called chemical weathering. Water seeps into cracks and gradually dissolves the rock, widening the cracks until, over thousands of years, the limestone becomes riddled with caves and passageways. Water flowing through caves forms underground streams, rivers, and pools (such as this one in Mexico). Surface rivers disappear into sink holes and reappear many kilometres away. Eventually a cave roof may fall in, creating a gorge.

Copyright © 2007 Dorling Kindersley

highlights

Top 10 Sweet 16 Birthday Gifts
Your daughter's sweet 16 is a big milestone in her life. Celebrate this special occasion with one of these top gifts for girls turning 16.

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, brought to you by Galactic Hot Dogs.

Printable Lists of the Top 100 Baby Names
Need help with baby name ideas? Use our printable list of the top 100 girl names and top 100 boy names of 2015 to help you brainstorm and narrow down your favorites.

Registered for Kindergarten — Now What?
Wondering what to do now that you've signed your child up 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