岩石对我们每个人来说是再常见不过的东西了,它是我们地球主要的组成部分。石头看似普通,其实也大有文章在。认识一些岩石,不仅使我们开拓眼界,还能让我们的郊游增添的乐趣,甚至发现神秘的宝矿呢。岩石都是由矿物组成的,不同的岩石中含有不同的矿物,因此寻找矿藏离不开对岩石的认识。岩石分很多种类,其中的成分千差万别,它们形成的年龄也有大有小。不同的岩石会告诉我们不同的地质状态甚至远古时候的生命信息。岩石与人类的生产生活密切相关,人类走向文明的开始就是把石头当作工具举过头顶啊。在这里,不仅有通俗的文字供你阅读,还有很多精美的岩石和矿物的图片呢。欢迎你来慢慢浏览,相信会有收获的。 ····························································································································· 先来认识一些岩石吧
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白石英岩
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地球上的所有东西都是有化学元素组成的,岩石也不例外。岩石在压力、温度等环境因素中会发生这样那的物理变化和化学变化,进而产生各种各样的岩石。不同的岩石,其化学成分也不相同,因此,对岩石的分析离不开对它们化学成分的研究。我们不会过多涉及岩石的化学变化,只要知道石头也有很多种,而且它们也不是一成不变的。 科学家们将岩石分成三大类, 一类叫火成岩。它们原来就是地下炽热的岩浆,有些喷出地面冷却后形成岩石,有些在地下就凝固了。这类岩石中有我们常见的花岗岩,也有不常见的玄武岩等; 一类叫沉积岩。顾名思义,它是由一些物质沉积到一起而形成的。比如沙子、淤泥、火山灰等等,这些东西堆积到一起,年长日久会产生石化作用而变成岩石。如页岩、砂岩、石灰岩等就属于沉积岩; 一类叫变质岩。它原先就是岩石,后来由于温度、压力变高,内部的成分和结构发生了变化,形成了另一类岩石,这样的岩石如片岩、大理岩、糜棱岩等。 地球上这三大类岩石并不同样多,分布的位置也不同。沉积岩主要分布在陆地的表面,约占整个大陆面积的75%。从地表面往下,越深则越少,而火成岩和变质岩则越来越多。到了地壳深处和上地幔那里,就主要是火成岩和变质岩了。火成岩占整个地壳体积的64.7%,变质岩占27.4%,沉积岩则只占7.9%。其中玄武岩和辉长岩占全部火成岩的65.7%,花岗岩和其他浅色岩约占34%。由此我们就知道了,地球上什么岩石最多啦。 不同的岩石都有它们自己特定的比重,也就是说我们如果将它们放在弹簧称上时,它们的重量会不一样。岩石抗压力和拉力的的强度也不一样等等,这些都叫做岩石的物理性质。人们在盖房子、钻探等工程建设中都要考虑到岩石的各种物理性质,否则就可能发生意外。岩石受力后会发生变形,如果这个力超过了它能承受的范围,它就会破裂。 岩石里面含有很多矿物质,一般主要的有硅酸盐矿物(如长石、云母、角闪石、辉石、橄榄石)和石英;其次是各种氧化物矿物(如磁铁矿、钛铁矿、金红石)、碳酸盐矿物(如方解石、白云石)、磷酸盐矿物(如磷灰石);有时含某些硫化物、硫酸盐或含有某些放射性物质或贵金属元素矿物,或者具特种性质的矿物(如金刚石)。如果岩石中所含的这些矿物质在岩体中比较集中,就具备了可开采的经济价值,就成为了矿产。各种金属和非金属矿产以及煤炭、石油等能源资源,绝大多数都存在于各类岩石中,并与岩石的成因有关系。所以,人们说岩石是各类矿产的载体和巨大能源库。往往找到某种岩石也就找到了某种矿藏。 岩石中还包括比较特殊的一类,那就是陨石和月球岩石。陨石是不请自来的天外“客人”,月球岩石则是我们人类专程请到地球上来的。这类岩石对于人类了解太阳系,了解地球自身都非常珍贵。 最后要提一下,目前我们所见到的各种岩石并不是一直存在且亘古不变的。可以做这样一个描述:在大洋底的地壳裂缝处,地壳已经非常薄。那里日日夜夜都在涌出岩浆来。正是这些岩浆在不停地更新着地球上的岩石。地壳及大陆板块的运动,使沧海变桑田,桑田变沧海。新形成的洋底有一部分会被抬升,形成大陆上的高山,像青藏高原就是距今最新形成的。那里的岩石记录着过去海底世界的故事。构成这些高山的年轻岩石,有一天还要变老,它们会被风化成沙和泥土,最终风吹水漂地沉积到某些方而再一次变成岩石——沉积岩。它们有一天还要随着大陆板块的运动而钻入地下更深入,回到它们的老家再一次成为岩浆。在这样的运动中,还有一个目前不太经常普遍的形式就是火山。因此说,地球虽然已经有四五十亿的年龄,但要想找到那样年龄的岩石却是不可能的事情啦。迄今,科学家找到的最古老的岩石约38亿岁,是在北美格陵兰发现的。没有永远不变的东西,即使是最坚硬的石头。这就是物质的运动规律。 ····························································································································
铁陨石
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下面再来了解一下岩浆 岩浆是地球内部的炽热熔体,其中最多也是最重要的就是硅酸盐岩浆。岩浆可以在地下深处移动,也可以喷出或流出地表面。岩浆的温度一般约为700~1200摄氏度,不同成分的岩浆温度也有所不同。不同岩浆的粘稠度也不一样,有的稀一些,有的稠一些。越稠的岩浆温度也越高。猛烈爆发的火山喷出的往往是很稠的岩浆。不同岩浆产生的情况也不一样,有的是大洋板块进入地幔被熔化,有的是在大陆地壳内部因地热升高而形成。岩浆在多种地质作用下,会发生多种变化,形成多种火成岩。 ························································································································································································
岩石与人们的生活息息相关,下面去采石场看看
采石是指在露天为得到石料而进行的一种挖掘。采得的石料分为两种,一种是碎石块;一种是成形的,叫型材。采石之前,人们先要清除岩石层表面的土壤或是风化了的岩石。采石的方法根据所需要的石材而定。可以爆破、可以钻凿等。有专门的机械可以将岩石切割成块,也可在岩石上打孔,再将楔子打进孔中以撑裂岩石。采得的石块可以很大也可以很整齐。它们将根据不同需要再次加工。石块运到加工场,可以锯成板材或车削成其他形状。石材经打磨、抛光后可以达到非常平整光滑的程度。 |
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