mackenzie mississippi missouri yukon colorado Rivers and Coasts Rivers and coasts are areas where water meets land Water shapes the landscape in many ways cutting away narrow mountain streams and wide curved rivers It forms rocky cliffs and long sandy beaches along coastlines FOCUS ON Colorado River page 14 This map shows the main rivers of the world FOCUS ON Venice page 29 Rivers Channels of freshwater that flow across land are known as rivers They start in high ground and flow downhill to the ocean Rivers gain more water as they flow closer to the sea becoming wider and deeper 4 Amazon Parana Uruguay Water cycle The movement of water from high ground to low ground through rivers is an important part of the water cycle The water cycle is the way in which water moves from Earth’s surface to the atmosphere and back again
5 There are 221,208 miles 356,000 km of coastline on Earth If you laid out every coastline in a straight line it would almost reach from Earth to the Moon Coasts Rough waves and high tides carve different landscapes along the coast The movement and force of water creates many types of coasts such as beaches and cliffs FOCUS ON UK coast page 18 Amur Yellow Danube Ob Yenisei Volga Ganges Yangtze Mekong Nile FOCUS ON Three Gorges Dam page 26 Congo Zambezi FOCUS Ganges River page 8 Darling Murray FOCUS ON Twelve Apostles page 23
River Structure Rivers start out in high areas as narrow fast-flowing streams They become wider and slower as they move downhill toward the sea Source The source is the place where a river starts Rivers can begin as springs where water comes to the surface from deep underground Some emerge as tiny streams of water from melted glaciers or pools of rainwater which run downhill Finding a source It can be difficult to decide exactly where a river begins In some cases there are many small streams that all flow into the same large river Geographers usually consider the source to be the furthest point upstream on the longest tributary Tributaries are small streams or rivers that flow into larger rivers Some rivers begin in damp boggy marshlands In these cases the highest part of the marshland is considered the source of the river Upper course Near the source rivers do not contain much water They are narrow shallow channels that flow quickly downhill This stage is known as the upper course 6
Middle course In the middle course rivers slow down as they flow over flatter ground Tributaries join the river and add more water to it This makes the river wider As the river flows over the ground it picks up sediment that makes the water murkier Lakes Some water that falls to the ground also drains into lakes Unlike rivers the water in these lakes is calmer Many lakes have connecting rivers although some are totally isolated Lower course Rivers slow down and become wider as they cross flat ground This stage is called the lower course Rivers are often very deep in the lower course River basins When it rains water that falls to the ground flows overland or underground toward a river The area of land that is drained by a river is known as a river basin This water is then carried to the sea by the river as part of the water cycle The Amazon River has the largest river basin on Earth Around 20 percent of all water carried to the ocean by rivers is carried by the Amazon River Mouth The mouth of the River Minho in northern Portugal marks the border between Spain and Portugal The place where a river meets the ocean or a lake is known as its mouth All of the water from the river empties into the ocean or a lake When rivers empty into the ocean they create a mixture of freshwater and salt water in the area around the mouth 7
