GenreGenre Comprehension SkillComprehension Skill Text FeaturesText Features Science ContentScience Content Nonfi ctionNonfi ction Compare andCompare and • Captions• Captions Rocks and SoilRocks and Soil ContrastContrast • Diagrams• Diagrams • Labels• Labels • Glossary• Glossary Scott Foresman Science 3.7Scott Foresman Science 3.7 ì<(sk$m)=bdicij<ì<(sk$m)=bdicij<ISBNISBN 0-328-13828-20-328-13828-2 +^-Ä-U-Ä-U+^-Ä-U-Ä-U
Vocabulary Extended Vocabulary What did you learn? decay delta igneous rock drought 1. What makes a fertile fl ood so good loam famine for the farmers and the community? metamorphic rock fertilize mineral floodplain 2. What are some of the natural events nutrient irrigate that will cause the rivers to flood in rock oasis Bangladesh? sedimentary rock by Kristin Cashore soil 3. What makes the Okavango River different from the other rivers you read about in this book? 4. In this book you read about the flooding of the Nile River and the building of the Aswan High Dam. Write to explain how the Aswan High Dam has changed the Picture Credits Every effort has been made to secure permission and provide appropriate credit for photographic material. behavior of the Nile River. Give The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). examples of both good and bad 1 Mike Surowiak/Getty Images; 6 ©Airphoto; 9 (T) Robert Harding World Imagery/Alamy Images, effects of the Aswan High Dam. (B) John Hepver/The British Museum/DK Images; 11 NASA/Photo Researchers, Inc.; 12 (B) Trygve Bolstad/Panos Pictures; 13 Ian Berry/©Magnum Photos; 14 (BL) Martin Harvey/NHPA Limited. Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson. 5. Compare and Contrast What are the similarities between irrigating ISBN: 0-328-13828-2 and fertilizing? What are the Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. differences? This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05
What You Already Know A rock is a solid, nonliving material made Crops grow best in soil that has a lot of water of minerals. There are three kinds of rock. and nutrients. One of the best soils for crops Igneous rock forms from molten minerals and is called loam. gases. Sedimentary rock forms from sediments. Metamorphic rock is rock that has been changed Most land gets its water from rain. However, because of heat, pressure, or both. some places get their water through flooding. People Minerals form from nonliving matter. usually think of floods as being harmful events that You can identify a mineral by its color, streak, hurt the land and its living things. But some floods and other properties. Most things that we use bring water and needed nutrients to dry land. In this contain minerals. book you will learn about these kinds of floods. Air, water, and rock particles make up three of soil’s four ingredients. Sands, silts, and clays account for soil’s rock particles. These rock flooded rice fi eld particles contain minerals that are rich in nutrients. The fourth ingredient in soil is humus. Humus is made up of dead and decaying plants and animals. metamorphic rock 2 3
Facts on Floods Farmers often grow rice near fl ooding rivers. Rice grows well in this flooded paddy fi eld. Floods are caused by overflowing bodies of water, including rivers, lakes, and streams. They Historically, rivers like the Nile in Egypt have are also caused by groundwater rising up to the flooded regularly. The Nile’s waters irrigate surface and overflowing the land. When the soil the land. Irrigation makes the soils of the Nile becomes saturated, meaning when it can’t hold floodplain some of the most fertile in the world. any more water, its water table, or the top layer Quick quiz: What did the ancient civilizations of of groundwater, floods the land. Egypt, Mesopotamia, China, and India all have in A flood can be one of the most harmful common? Answer: They all developed along huge forces in nature. It can harm people and crops, rivers. The irrigation provided by their rivers’ ruin homes, and spread diseases. However, there annual floods supported farming, trade, and many are some places where floods bring important other activities. benefits. People depend on some annual floods to Flooding rivers carry silt. This silt is rich bring water and minerals to the land. in nutrients. It fertilizes the land and creates productive farmlands when flood waters deposit it there. If it weren’t for these fertile floods, drought and famine might happen in many places. river in fl ood floodplain The Thames (TEMZ) Flood Barrier was The fl oodplain is the low area covered built to prevent flooding in London. by a river during a fl ood. 4 5
Deltas For people who live near these deltas, the river can be both a friend and an enemy. If the river does not flood enough, people may So how does a flooding river work? As suffer drought and famine. If it floods too much, it moves downhill over rocks and land, it then property is damaged and people are hurt. So collects soil particles rich in nutrients. When everyone hopes the river floods just enough! the river reaches flatter ground, it slows down. When rivers flood, they do more than irrigate Most rivers flow into a lake, sea, or ocean. floodplains and spread minerals. They also change When a river reaches the lake, sea, or ocean, the shape of the land. Some land gets eroded, or it drops its particle load. Over a long period washed away. Other land gets this washed away of time, this material forms an area of land at material, which builds up. And the river itself the mouth of the river, called a delta. Deltas sometimes changes its course. are made fertile by the nutrients they receive To prevent such changes, many from floods. There are fertile deltas all over countries have dammed their major the world. rivers. Later you will read about the damming of the Nile and its results. Rivers move quickly on steep land. When they reach level land, they slow down and spread out. Floodplain The Mississippi Delta covers an enormous amount of Delta land in the southeastern United States. 66 77
The Nile The Nile River is the longest river in the The Nile brings life to the dry lands on either side of it. world. It has always been the center of life for Egyptians. The capital of Egypt, Cairo, is on When the Nile flooded, it made the narrow the Nile. So is Khartoum, the capital of Sudan. strip of land on either side of the river very Farther to the south, a branch of the Nile begins fertile. The flooding river provided the water and at Addis Ababa, the capital of Ethiopia. nutrients needed to grow crops. Although the Nile flows for hundreds of miles Sometimes the river rose too much or not in Egypt, it gets its water from countries such enough. In the worst years it didn’t rise at all, as Ethiopia. It rains a lot in Ethiopia during the leading to terrible drought and famine. The corn, summer. For thousands of years the Nile carried rice, wheat, and other crops grown along the the water from Ethiopia’s rains all the way to Nile needed a lot of people to tend to them, so Egypt. In the past this caused flooding. families started having more children. This made the famine years even worse, because there were These fertile fi elds were watered so many more mouths to feed. by the fl ooding of the Nile. The Egyptian government decided to take steps to try to solve the problems created by drought and famine. They built the Aswan High Dam. ancient Egyptian carving of a farmer plowing a fi eld 8 9
The Aswan High Dam, built in This is a satellite image 1970, has stopped the Nile’s annual of the Aswan High Dam. The dam holds floods and controlled the water back a huge reservoir supply. During rainy years it stores of water. water. During times of drought EGYPT Aswan Ni High Dam it releases water. The dam also le generates electricity for all of Egypt. The Aswan High Dam keeps Aswan High Dam people and houses safe from Lake Nasser floods. It also helps prevent SUDAN drought and famine. However, the The Nile River dam has also had some very bad and the Aswan effects. By stopping the floods it has High Dam prevented the silt suspended in the water from reaching the land. This has forced Egyptian farmers to use man-made fertilizers. Because the dam held back As time passes, their land grows more dry and the flow of the Nile, some of unhealthy without the traditional silt deposits. the lands behind the dam were permanently flooded. Thousands These temple of people who lived on these lands ruins needed to be moved to had to leave their homes. Some higher ground ancient Egyptian relics were lost after the under the water. The Egyptians Aswan High Dam was built. tamed their wild river, but their land would never be the same. 10 11
Bangladesh Farmers in Bangladesh are used to flooding. Many of them build their houses Bangladesh is a small on stilts. That way when Brahmaputra country near India. The the floods come, the people Gan ges BANGLADESH deltas of three big rivers, the don’t have to leave! However, Me Ganges, the Brahmaputra, and some years the flooding gh na the Meghna, form much of causes terrible devastation. Many Bangladeshi people Bangladesh’s land. These It harms people and animals, have adopted ways to rivers start all the way up in washes away houses, and live above the fl oods. Bangladesh’s the Himalayas. They end at destroys crops. The farmers flooding regions the Indian Ocean. who live near Bangladesh’s Bangladesh floods if there is a rivers must always be alert. lot of snow melting in the Himalayas. It also floods if there is heavy rain upstream in India and elsewhere. The yearly rainstorms, called monsoons, also flood Bangladesh. The floods bring rich silt deposits, which make Bangladesh one of the most fertile places in the world. Bangladesh’s flat land and many rivers fl ood easily. 1212 1313
Okavango Delta Whenever a river floods, it can cause destruction. But sometimes people depend upon floods to fertilize and irrigate their The Okavango River originates in Angola lands. Sometimes flooding even helps plants and flows through Namibia and Botswana, in and animals. southern Africa. This river is unique. It does not Rivers are not predictable. Sometimes they’re end at a lake, sea, or ocean. Instead, it ends at a supposed to rise, but fail to. Other times they wetland in the middle of the Kalahari Desert. do rise, but when they’re not expected to! In the This wetland is called the Okavango Delta, and best years, rivers rise just the right amount, at it is one of the largest inland deltas in the world. just the right time. This is when the people and The Okavango Delta is an oasis of life in the land are happy to have a fertile flood! the harsh desert. It floods every summer. This flooding irrigates and fertilizes the delta so that These elephants would not have a variety of plants and animals enough to eat if it weren’t for the flooding of the Okavango. can grow and live there. ANGOLA Ok av an go Okavango Delta NAMIBIA BOTSWANA Okavango Delta The annual floods of the Okavango bring life to the Kalahari Desert. 1414 15
Vocabulary Extended Vocabulary What did you learn? Glossary decay delta igneous rock drought 1. What makes a fertile fl ood so good delta an area of land that usually forms for the farmers and the community? loam near the mouth of a riverfamine metamorphic rock fertilize mineral floodplain 2. What are some of the natural events drought a severe shortage of water, that will cause the rivers to flood in nutrient caused by lack of rain or lackirrigate rock oasis Bangladesh? of expected flooding sedimentary rock soil 3. What makes the Okavango River famine a food shortage that causes severe different from the other rivers you hunger and starvation read about in this book? fertilize to supply the minerals and 4. In this book you nutrients that plants need to grow read about the flooding of the Nile River and the building of the Aswan floodplain the area on either side of a river High Dam. Write to explain how the that is covered with water during Aswan High Dam has changed the Picture Credits a flood behavior of the Nile River. Give Every effort has been made to secure permission and provide appropriate credit for photographic material. The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). examples of both good and bad irrigate to transport water to plants to effects of the Aswan High Dam. 1 Mike Surowiak/Getty Images; 6 ©Airphoto; 9 (T) Robert Harding World Imagery/Alamy Images, (B) John Hepver/The British Museum/DK Images; 11 NASA/Photo Researchers, Inc.; 12 (B) Trygve Bolstad/Panos Pictures;help them grow 13 Ian Berry/©Magnum Photos; 14 (BL) Martin Harvey/NHPA Limited. Unless otherwise acknowledged, all photographs are the copyright © of Dorling Kindersley, a division of Pearson. 5. Compare and Contrast What are oasis a fertile spot in the middle of the similarities between irrigating the desert, caused by the presence and fertilizing? What are the ISBN: 0-328-13828-2 of water differences? Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. This publication is protected by Copyright, and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025. 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 0516
Affichage des 10 premières pages. Téléchargez le document pour le voir en entier.
Aucun commentaire pour le moment. Soyez le premier !
Commentaires (0)
Aucun commentaire pour le moment. Soyez le premier !