甚麼是化石? What are fossils?

　　化石“Fossil”一詞源自拉丁文的“Fossillis”，解作「挖掘」的意思。化石是指埋藏在地層中的古生物遺體、遺物或痕跡，經過長時間礦物化的交替作用，最後形成化石，但化石形成的機率仍相當低，而且通常只會留下抵抗性較強的古生物硬體部分。古生物化石除了大部份都是保存於岩石之中外，有些還可以在琥珀、瀝青或凍土層中找到。
　　化石可讓我們了解生物之演化和地球的歷史，是地球上一種不可再生的天然產物，所以化石都是十分之珍貴，具有很高的科學研究價值，另外亦有觀賞和收藏的價值。
　　 The word “Fossil” originates from Latin “fossillis” which means “obtained by digging”. Fossils refer to the petrified living organisms and remains in strata. It could only be formed when the bodies of lives were buried immediately after they deceased and followed multitudinous years of replacement and re-crystallization reaction. Fossil is such a kind of precious non-renewable natural resources with high scientific research value.

化石可分為四大類 There are four main types of fossils

1.實體化石 ( Body fossil )
2.模鑄化石 ( Mold and cast fossil )
3.遺跡化石 ( Trace fossil )
4.化學化石 ( Chemical fossil )

化石的形成 The Formation of Fossils

　　化石的形成是一個非常艱難的過程，需要許多特殊條件配合，可能要用上數十萬年，甚至百萬年才能形成，首要條件是生物死後需要被迅速地埋藏，生物的軟體部分一般會先被分解，只留下較堅固的硬體部分，如牙齒、骨骼或外殼等。然後，這些存留的部分在地層中經過長時間物理化學作用的改造，稱為「石化作用」，它們被地層中的礦物質填充和交替，最後形成化石，生物的原貌及結構都能在化石中保存下來。
　　 The formation of fossils undergoes complex process that requires many special conditions through hundred thousand or even million years. Fossils could only be formed when the bodies of lives were buried immediately after they deceased. The soft tissues would be dissolved and the hard tissues including teeth, bones and shells could be retained and followed multitudinous years of replacement and re-crystallization reaction. Most of the appearance and structures of the ancient organisms could be preserved in the fossils.

圖一：生物死後迅速地被泥土等沉積物埋藏起來。
Figure 1: The bodies of lives were buried immediately by sediments after they deceased.

圖二：生物的肌肉和軟組織一般會腐爛並分解，只留下較堅固的骨骼部分。
Figure 2: The muscles and soft tissues would be decayed and dissolved while only the hard tissues could be retained.

圖三：存留的部分在地層中經過長時間的礦物質填充和交替，進行了「石化作用」，最後形成化石。
Figure 3: Fossils could be formed when the retaining parts carried out multitudinous years of replacement and re-crystallization reaction.
圖四：經過地殼運動、表層岩石的風化作用或人為的挖掘，埋藏在地層中的化石暴露於地面。
Figure 4: The fossils in the strata would be exposed by plate tectonics, weathering and human factors.

圖一：生物死後迅速地被泥土等沉積物埋藏起來。 Figure 1: The bodies of lives were buried immediately by sediments after they deceased.	圖二：生物的肌肉和軟組織一般會腐爛並分解，只留下較堅固的骨骼部分。 Figure 2: The muscles and soft tissues would be decayed and dissolved while only the hard tissues could be retained.
圖三：存留的部分在地層中經過長時間的礦物質填充和交替，進行了「石化作用」，最後形成化石。 Figure 3: Fossils could be formed when the retaining parts carried out multitudinous years of replacement and re-crystallization reaction.	圖四：經過地殼運動、表層岩石的風化作用或人為的挖掘，埋藏在地層中的化石暴露於地面。 Figure 4: The fossils in the strata would be exposed by plate tectonics, weathering and human factors.