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  • General

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  • 石化类型

    A preserved frozen elephant specimen displayed in a museum, showcasing fossilization.
     

    Where could you find the best fossils?
    ::哪里能找到最好的化石?

    The best  fossils  would probably be ones that you could get DNA from. DNA holds the  genes  of an organisms. The genes could tell scientists a lot about what the organisms was really like. Where could you find a fossil with DNA? How about a melting  ? You might be able to find a creature that had been frozen into the ice for a long time. A frozen animal would be very well preserved!
    ::最好的化石可能是你能从中获取DNA的。 DNA掌握着生物的基因。 这些基因可以告诉科学家很多关于生物的真象。 你在哪里能找到有DNA的化石? 如何熔化? 你也许能找到一个被冰冻了很长时间的生物。 冷冻的动物将会得到很好的保存!

    How Fossils Form
    ::化石如何形成

    The process by which remains or traces of living things become fossils is called  fossilization  ( Figure   ). Most fossils are preserved in sedimentary  .
    ::活物的残骸或痕迹成为化石的过程被称为化化化(图)。 大多数化石保存在沉积中。

    Fossils in Sedimentary Rock
    ::沉积岩中的化石

    Most fossils form when a dead organism is buried in  sediment . Layers of sediment slowly build up. The sediment is buried and turns into  sedimentary rock . The remains inside the rock also turn to rock. The remains are replaced by  . The remains literally turn to stone. This type of fossilization is called  permineralization .
    ::沉积层慢慢积聚,沉积层被掩埋,沉积层变成沉积岩,岩石中的遗骸也变成岩石。遗骸被岩石所取代。遗骸被石头所取代。这种化石的化石形式被称为矿化。

    Flowchart depicting ammonite fossilization process from death to rock layers.
     
    Fossilization. This flowchart shows how most fossils form.

    Other Ways Fossils Form
    ::其他方式 化石形式

    Fossils may form in other ways. With complete preservation, the organism doesn't change much. As pictured below ( Figure   ), tree sap may cover an organism and then turn into  amber . The original organism is preserved so that scientists might be able to study its DNA. Organisms can also be completely preserved in tar or ice.
    ::化石可能以其他方式形成。 完整保存后, 有机体不会发生太大变化。 如下文( 图表 ) 所示, 树苗可能覆盖有机体, 然后变成琥珀。 原始有机体被保存, 这样科学家就可以研究其DNA。 生物也可以完全保存在焦油或冰块中。

    A spider preserved in amber, demonstrating complete preservation as a fossil.
     
    Complete Preservation. This spider looks the same as it did the day it died millions of years ago!

    Molds  and casts are another way organisms can be fossilized. A  mold  is an imprint of an organism left in rock. The organism's remains break down completely. Rock that fills in the mold resembles the original remains. The fossil that forms in the mold is called a  cast  ( Figure   ). Molds and casts usually form in sedimentary rock. With  compression  ( Figure   ), an organism's remains are put under great pressure inside rock layers. This leaves behind a dark stain in the rock.
    ::模具和石膏是另一种可以使生物化化的方式。模具是一块留在岩石中的有机体的印记。 生物体的残骸完全碎裂。 填满模具的岩石与原始遗骸相似。 模具中的化石称为石膏( Figure )。 模具和石膏通常形成于沉积岩中。 压缩后( Figure ) , 生物体的残骸在岩石层中受到巨大压力。 这留下了岩石中的暗色。

    Two fossilized leaves displayed on rock, demonstrating examples of mold and cast fossilization.
     
    Molds and Casts. A mold is a hole left in rock after an organism's remains break. A cast forms from the minerals that fill that hole and solidify.
    Fossilized remains showing three impressions resembling plant leaves or flowers.
     
    Compression. A dark stain is left on a rock that was compressed. These leaves were fossilized by compression.

    Why Fossilization Is Rare
    ::为什么化石化是稀有的

    It’s very unlikely that any given organism will become a fossil. The remains of many organisms are consumed. Remains also may be broken down by other living things or by the  elements . Hard parts, such as bones, are much more likely to become fossils. But even they rarely last long enough to become fossils. Organisms without hard parts are the least likely to be fossilized. Fossils of soft organisms, from bacteria to jellyfish, are very rare.
    ::任何特定生物都不太可能成为化石。 许多生物的残骸都被消耗掉。 残留物也可能被其他生物或元素分解。 骨骼等硬部分更有可能成为化石。 但即使它们也很少长到能成为化石。 没有硬部分的有机体最不可能化石化化。 从细菌到水母,软有机体的化石非常罕见。

    Summary
    ::摘要

    • Very few fossils preserve soft parts. Insects may be preserved in amber. Insects and other animals may be preserved in ice.
      ::很少有化石保存软部分,昆虫可以保存在琥珀中,昆虫和其他动物可以保存在冰中。
    • Some fossils are created when minerals replace the organic material. This is called permineralization.
      ::有些化石是矿物取代有机材料时产生的,这称为杂质化。
    • A fossil may be in the form of a mold. A mold is the depression left in the shape of the material.
      ::化石可能以模具的形式出现,模具是物质形状留下的抑郁症。
    • A fossil may be preserved as a cast. A cast is the rocky material that fills the mold.
      ::化石可以作为石膏保存,石膏是填满模具的岩石材料。

    Review
    ::回顾

    1. Why are there so few fossils of soft parts?
      ::为什么有这么少的软零件化石?
    1. A snail shell is buried in mud. The shell is filled with mineral-rich water. What type of fossilization has occurred?
      ::螺壳被埋在泥土中,罐壳里装满了富含矿物质的水。发生了何种化石化?
    1. Compare and contrast molds and casts.
      ::比较和对比模具和石膏。
    1. Why is fossilization rare?
      ::为什么化化化稀罕?

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

     

     

    1. What are fossils?
      ::什么是化石?
    1. What type of rocks are fossils found in?
      ::化石在什么种类的岩石中被发现?
    1. What are sediments?
      ::什么是沉积物?
    1. How does a bone from a dead organism harden to become a fossil?
      ::死去的有机体的骨头怎么会硬起来 变成化石呢?
    1. What happens as the bone is buried?
      ::骨头埋起来后会怎样?
    1. What factors exposed the rock layers with the fossils in it?
      ::哪些因素暴露了岩石层 里面有化石?