Geological Timeline 地质纪年表
The Earth is over 4.6 billion years old. The Geological Timeline divides the Earths existence into sections where different types of events were occurring. There are 6 major divisions in the earths history which are grouped into two categories.
地球已有46亿年的历史。地质纪年表以不同的重大事件为界限把地球划分为几个地质时代。主要分为两类，共包括6大地质时代。
Precambrian |prēˈkambrēən, -kām-| Adjective: Geology
extended from the origin of the earth (believed to have been about 4.6 billion years ago) to about 570 million years ago, representing 87% of geological time.
前寒武纪
开始于地球形成时期（大约46亿年前）结束于5亿7000万年前，占了地史的87%。
Phanerozoic |ˌfanərəˈzōik| Adjective: Geology
Relating to, or denoting the time since the beginning of the Paleozoic era, and comprising the Mesozoic, and Cenozoic eras. This is the the time where life evolved on earth.
显生宙
开始于古生代时期，还包括中生代和新生代。这一时期生物开始进化。
| Pre-Archean (Hadean) 前太古宙（冥古宙） | The first geological era where the formation of the earth began. | 前太古宙 第一个地质时代，这时地球开始形成。 |
| Archean 太古宙 | During the Archean era the earths temperature was approximately 3 times higher than the current temperature today, and volcanic activity was considerably higher during this time. | 在太古宙时期地球温度大约是现今的3倍，而且此时期的火山活动性相对较高。 |
| Proterozoic 元古宙 | The most important events of the Proterozoic era is the formation of oxygen in the Earths Atmosphere. The development of the first single cell organisms also coincides with the accumulation of free oxygen in the atmosphere. | 元古宙时期最重要的是大气中氧的形成，伴随着自由氧的存在第一个单细胞有机物出现了。 |
| Paleozoic 古生代 | Dramatic changes in geological and climate change occurred during this era. The largest diversification of life in earths history also occurred; however this era is marked with the largest mass extinction in the history of the Earth. | 古生代时期地质和气候变化非常显著，同时地球上最大的生物物种多样化也在这一时期出现，但是该时期也被标注为地球史上最大物种灭绝时期。 |
| Mesozoic 中生代 | Meaning “middle life” and is the era also referred to as the “Age of Reptiles” . During this time Dinosaurs evolved as the dominate species on earth before becoming extinct. | 意味“中间的生活”，也称为“爬行动物时代”，在这一时期恐龙作为主导物种渐渐进化并灭亡。 |
| Cenozoic 新生代 | Also known as the “Age of Mammals”, with the demise of large reptiles the diversification of smaller mammals occurred. | 这一时期随着爬行动物的灭绝和哺乳动物的出现也称为“哺乳动物时期”。 |