The Three Types of Rocks
岩石的三种类型
All rocks are not the same, even though many of them look alike. There are three main types or classes of rock: sedimentary, metamorphic, and igneous. The differences between each of the rocks have to do with how they are formed. This is what determines the type of rock it is.
所有的石头是不一样的，尽管其中许多看起来一样。主要有三种类型的岩石：沉积岩，变质岩，火成岩。每个岩石之间的差异主要在于它们不同的形成方式。而如何形成也决定了岩石的类型。
The first type of rock is sedimentary. A sedimentary rock is formed from particles of sand, shells, pebbles, and other pieces of material. All of these particles together make up sediment. Sediment is the result of material broken down by weathering or erosion.
第一种类型的岩石是沉积岩。沉积岩形成于沙砾，贝壳，鹅卵石，或其他的物质的细小颗粒。所有这些颗粒共同组成了沉积岩。沉积岩是风化和侵蚀分解的结果。
Slowly, the sediment accumulates in layers and over a long period of time it will harden into rock. Sedimentary rock, usually, is fairly soft and may break apart very easily or crumble into pieces. If sedimentary rock is broken apart inside is sand, pebbles, or stones in the rock. Sedimentary rock is usually the only type of rock that also contains fossils. Fossils are the remains of once living animals or plants usually from long ago.
沉积物缓慢的层层聚积，长时间后就会硬化成岩石。沉积岩通常是相当柔软，很容易掰开或是破碎成片。沉积岩破裂，岩石内部是沙子，卵石。通常情况下，沉积岩是唯一含有化石的岩石。化石通常是指很久很久以前曾经有生命的动物或植物的遗迹。
Examples of sedimentary rock types include limestone, shale, and sandstone.
沉积岩包括石灰岩，页岩和砂岩。
The second type of rock is metamorphic. A metamorphic rock is formed under the surface of the earth from the change that takes place because of intense heat or pressure. In nature, it takes millions of years for a metamorphic rock to be formed. The rocks that result from this very long process often has ribbon-like layers and many shiny crystals. The crystals are formed by minerals which grow slowly over time on the surface of the rock.
第二种类型的岩石是变质岩。变质岩是在高温或强压导致的地形变化的地表形成。自然界形成一颗变质岩需要上百万年。从这个漫长的过程导致岩石常呈带状并含有许多有光泽的晶体。该晶体由随时间缓慢增长在岩石表面的矿物形成。
Examples of metamorphic rock types include gneiss, marble, slate, and quartzite.
变质岩类型的例子包括片麻岩，大理石，板岩，石英岩。
The third type of rock is igneous. Igneous rocks form when magma cools and hardens. Magma is the molten rock deep within the earth. The same material inside a volcano. Sometimes this magma, though, cools inside the earth. At other times it will erupt onto the surface from a volcano. When magma leaves the volcano it is called lava.
第三类岩石是火成岩。岩浆冷却变硬形成火成岩。岩浆是地球内部深处的熔岩。与火山内的物质相同。有时，这种岩浆在地球内部就冷却了。而在其他时候，它会爆发到从火山表面。当岩浆离开火山它被称为岩浆。
When this lava cools very quickly, no crystals form and the rock will look shiny and glasslike. Sometime there are gas bubbles trapped inside the rock during the cooling process of the magma. If this occurred there will be tiny holes and spaces left in the rock.
当熔岩快速冷却，无结晶形成，岩石便看起来有光泽，呈玻璃状。有时岩浆在冷却过程中残留了气泡。如果发生这种情况，岩石上会有微小的孔和缝隙。
Examples of igneous rock types include basalt, obsidian, pumice, and granite.
火成岩类型的例子包括玄武岩，黑曜岩，浮石，和花岗岩。
In summary, even though many rocks may look alike, there are three types of rocks with different characteristics. The three types of rocks are sedimentary, metamorphic, and igneous. Sedimentary are form from sediments that may include particles of sand, pebbles, or other stones. Fossils may also be found in sedimentary rock. Metamorphic rock takes millions of years to form and is formed by intense heat and pressure. They often are ribbon-like and contain shiny crystals. The last type is igneous rock, which forms when magma cools and hardens deep inside the earth. Magma is the same material inside of a volcano. All three rock types can be found in many places. Some examples of each include limestone, marble, and granite. Rocks are definitely not all the same.
尽管许多岩石可能看起来很相像，但是有具有不同的特点三种类型的岩石。这三种类型的岩石是沉积岩，变质岩，火成岩。沉积岩形成于沙砾，贝壳，鹅卵石，或其他的物质的细小颗粒。沉积岩中也能找到化石。变质岩的形成需数百万年，源于高温或强压。它们往往是带状，并含有有光泽的晶体。最后一类是火成岩，地球内部深处的岩浆冷却和固化形成火成岩。它与火山内部的物质相同。所有这三种类型的岩石可以在很多地方找到。举个这几种岩石的例子：石灰岩，大理石和花岗岩。岩石是绝对不一样的。
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