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3、成才路,状元成才路,状元成才路,状元成才路,状元成才路,黄河：我国的第二长河。干流全长5464千米，流域面积75.24万平方千米。发源于青海巴颜喀拉山脉，呈“几”字形，自西向东流经青海、四川、甘肃、宁夏、内蒙古、陕西、山西、河南、山东九个省区，最后在山东省北部注入渤海。,黄河下游,黄河下游,黄河上游,黄河源头,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,
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7、,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,词语解释,【叫苦不迭】 【忧患】 【摇篮】 【悬河】 【不折不扣】 【侵蚀】,朗读课文，说说文章的主要内容，并理清文章层次。,这篇课文介绍了黄河_、_ _及其_，告诉人们要_ _，_，否则就会受到_。,
8、变化的过程,变化,治理方案,保护大自,保护环境,大自然的惩罚,的原因,然,第一部分（ ）：有“中华民族的摇篮”之称的黄河，却因其在历史上的“表现”遭到质疑。 第二部分（ ）：黄河从“摇篮”变成了“祸河”，并分析了转变原因。 第三部分（ ）：写治理黄河的办法和人们决心改变黄河现状的迫切愿望。,1、2,36,7,人们都说，黄河是中华民族的摇篮。可是一查黄河近2000年来的“表现”，却叫人大吃一惊。,黄河发生了哪些变化呢？,黄河在近2000年间竟决口1500多次，改道26次，给两岸人民带来了深重的苦难。,过去的“摇篮”是什么样的呢？,自然条件很好,气候温暖,森林茂密,土地肥沃,我们的祖先在这里“生息
9、繁衍”（生活、养育后代）。,可是，后来黄河变了。,凶猛暴烈,折腾百姓,读第五自然段，思考：是什么引起黄河发生变化的？,黄河是世界上含沙量最大的大河，其含沙量相当于长江的68倍。黄河每年从中上游带到下游的泥沙总重量达16亿吨，其中12亿吨被搬到了大海，4亿吨则沉积在下游河道中。问题就出在这4亿吨泥沙上。它使黄河的河床逐年升高，结果有的河段高出两岸农田3米4米，有的甚至高出10米以上，使黄河成了悬河。,列数字,作比较,这段话运用了哪些说明方法？,河道：河水流经的路线，通常指能通航的河。,河床：指河流两岸之间容水的部分，也叫河槽或河身。,悬河：是河床高于地面，远远看去就像悬挂在半空中，故称悬河。,沉
10、积：指河流流速减慢时，水中所挟带的岩石、砂砾、泥土等沉淀下来，淤积在河床和海湾等低洼地带。,读第六自然段，思考：黄河发生变化的两个根本原因是什么？,一是自秦朝以后，黄土高原气温转寒，暴雨集中。加上黄土本身结构松散，很容易受侵蚀而崩塌，助长了水土流失，使大量泥沙进入黄河。,自然因素,气温转寒,暴雨集中,黄土松散,土地表面的肥沃土壤被水冲走或被风刮走。,二是人口迅速增长，无限制地开垦放牧，使森林毁灭，草原破坏，绿色的植被遭到严重破坏，黄土高原失去天然的保护层，引起了严重的水土流失。,人为因素,无限制地开垦放牧，破坏绿色植被,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状元成才路,状
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13、越穷越垦，黄河中的泥沙也就越来越多，因而黄河决口、改道的次数也就越来越频繁。,思考：这么多的“越”字说明了什么？,作者连续使用了12个“越”字，强调了人为因素造成了黄河泥沙的增加。以事实为例，分析透彻，点明人类的肆意破坏才是导致黄河变化的“罪魁祸首”。,无限制地开垦放牧,植被遭到严重破坏,水土流失,土壤肥力显著下降,农作物大量减产,人口迅速增长,读第七自然段，想一想：科学家为了治理黄河设计了哪些方案？,坚持牧、林为主的经营方向 保护森林资源 合理利用土地资源 修筑水利工程,谈谈你从这篇文章中受到的启示？,我们要保护大自然，保护环境，否则就会受到大自然的惩罚；人与自然要和谐相处，要合理地开发与利
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