作者：托福听力  梁晋

地质年代是指通过地壳上不同时期的岩石和地层所了解到的各地质事件发生的先后顺序和距今时间。主要时间表述单位：宙（eon）、代(era)、纪(period)、世(epoch)、时(age)。其包含了地球存在的时间跨度，从大约46亿年前到今天。托福听力和阅读中均有较多对于地质年代相关话题的考查。提前做好背景知识的积累，可以让大家在考试时更易理解文章的内容。下面详细介绍托福听力中常考的一些地质年代。

Phanerozoic Eon：The Phanerozoic Eon is the time from about 540-542 million years ago until now. It begins with the Paleozoic Era, which in turn begins with the Cambrian period. The key defining feature of the Phanerozoic Eon has been the activity of multicellular animal and plant life. Originally the Phanerozoic Eon took its name because this was the eon when life became manifested

显生宙：距今有5.4亿年的一段地质时期，开始于古生代 (Paleozoic Era) 的寒武纪时期 (Cambrian period)。显生宙的命名来自这一地质时期开始有生命的迹象。其特点为多细胞动物和植物的衍生。可细分为古生代、中生代和新生代。

Paleozoic Era: Paleozoic Era is a major interval of geologic time that began 541 million years ago with the Cambrian explosion, an extraordinary diversification of marine animals, and ended about 252 million years ago with the Permian extinction, the greatest extinction event in Earth history. The major divisions of the Paleozoic Era are the Cambrian, Devonian and Permian.

古生代：显生宙的个代。主要包括寒武纪、泥盆纪和二叠纪，在这个时期里生物开始繁盛。动物以海生的无脊椎动物为主，脊椎动物有鱼和两栖动物出现，植物有蕨类和石松等。二叠纪后期出现了地球史上的生物灭绝事件。

Cambrian：The Cambrian was the first geological period of the Paleozoic Era. it Began about 600 million years ago and brought about a surge of macroscopic species. It also produced a large amount of fossil records, like trilobite, opabinia, and anomalocaridids.

寒武纪：地球演化进程中古生代的开端，漫漫演化岁月中个生物物种大爆发的时代。与之前的生物爆发相比，寒武纪之初生物化石的门类与数量上升到了新的高度，在世界各地均有发现,以三叶虫，欧巴宾海蝎和奇虾为代表。

Devonian: Devonian Period is an interval of the Paleozoic Era, spanning between about 419.2 million and 358.9 million years ago. It is sometimes called the “Age of Fishes” because of the diverse, abundant, and, in some cases, bizarre types of these creatures that swam Devonian seas. Late in the period the first four-legged amphibians appeared, indicating the colonization of land by vertebrates.

泥盆纪:古生代的第二阶段。鱼形动物数量和种类增多，所以常被称为“鱼类时代”。同时，因地质运动许多地区露出海面成为陆地，脊椎动物进入飞跃发展时期。与之前地球生命几乎局限于海洋不同，植物、昆虫和两栖动物逐渐占据了陆地和淡水，大气中的氧含量也开始接近今天的水平。

Permian: Permian Period is the last period of the Paleozoic Era. It began 298.9 million years ago and ended 252.2 million years ago. At the beginning of the period, there was just one big continent. As the climate warmed up, plant and animal species began to diversify profusely. So life during the Permian Period was abundant and diverse. However, by the end of the period, hot and dry conditions were so extensive that they caused a crisis in Permian marine and terrestrial life, also known as the Permian Extinction

二叠纪: 作为古生代的终点，二叠纪是一个承上启下的阶段，具有划时代的意义。植物类在泥盆纪中得到发展，在二叠纪中更加繁茂。爬行类动物加速进化，物种的多样化正式形成。然而，史上规模的灾难也于此时悄然降临，由于气候变化、陨石撞击、海平面上升等多重因素影响，二叠纪发生了空前的生物大灭绝，以三叶虫为代表的超过90%的生物，彻底告别了世界。

Mesozoic Era: The Mesozoic Era is divided into the Triassic, Jurassic, and Cretaceous periods. It spread over an interesting time that witnessed splitting of the Pangaea supercontinent and the opening and spreading of the Atlantic and Indian oceans. It saw the evolution of the dinosaurs, the first mammals, early birds and the flowering plants.

中生代：显生宙的第二个代，分为三叠纪、侏罗纪和白垩纪。约开始于2.5亿年前，结束于6500万年前。这时期的主要动物是爬行动物，恐龙繁盛，哺乳类和鸟类开始出现。初期大陆是相连的，之后逐渐分裂成南北两片。

Triassic：The Triassic Period represents the transition from the Late Palaeozoic icehouse to the later Mesozoic greenhouse and was characterized by a relatively warm climate. In fact, it was conventionally considered as one of the warmest periods in Earth history. It is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic. Dinosaurs, which are perhaps the most popular organisms of the Mesozoic, evolved in the Triassic

三叠纪: 三叠纪是中生代的开端，距今约2.48至2.08亿年间。从中期之后，曾经所有陆地连在一起形成的超级大陆——“盘古大陆”，开始迈向分裂。气候变得异常暖和、干燥，生物在经历了二叠纪灭绝事件的深远影响之后，开始迎来复苏。我们熟知的恐龙，诞生于这一时期。

Jurassic: The Jurassic period was a geologic period in the middle of the Mesozoic. It extends from about 200 million years ago to 145 million years ago. During the Jurassic period, the dinosaurs continued their dominance of the land, while marine reptiles such as ichthyosaurs, plesiosaurs and marine crocodiles occupied the sea. During the Jurassic period, the world got progressively warmer and wetter, allowing for more forests on the continent Pangaea.

侏罗纪:界于三叠纪和白垩纪之间的地质年代。整个侏罗纪时期，气候处于温暖和潮湿的状态，生物发展史上出现了一些重要事件，引人注意，如恐龙成为陆地的统治者，鸟类出现，哺乳动物开始发展等等。侏罗纪前期，因为经历大灭绝，所以各种动植物都非常稀少，但其中恐龙一枝独秀。侏罗纪中晚期以后，恐龙成为地球上最繁荣昌盛的优势物种。

Cretaceous：Cretaceous Period was the last of the three periods of the Mesozoic Era. The Cretaceous began 145.0 million years ago and ended 66 million years ago; it followed the Jurassic Period and was succeeded by the Paleogene Period. The Cretaceous is the longest period of the Phanerozoic Eon. Spanning 79 million years. Over these years seas were elevated, spreading over large continental areas. The Cretaceous ended with one of the greatest mass extinctions in the history of Earth, exterminating the dinosaurs, marine and flying reptiles, and many marine invertebrates.

白垩纪: 白垩纪是中生代的最后一个纪，开始于1.45亿年前，结束于6600万年前，历经7900万年,是显生宙中最长的一个阶段。白垩纪的气候相当暖和，海平面的变化大。大陆被海洋分开，陆地生存着恐龙，海洋生存着海生爬行动物。新的哺乳类、鸟类出现，开花植物也出现。白垩纪-第三纪灭绝事件是地质年代中最严重的大规模灭绝事件之一，包含恐龙在内的大部分物种灭亡。

Cenozoic：The Cenozoic Era is the current geologic era of the Phanerozoic Eon and extends from 65.5 million years ago to the present. The Cenozoic is best known for the appearance and diversification of modern mammals and birds. Grasslands first appear in the Cenozoic and greatly influenced the evolution of many mammals. Humans first appear during the latter part of this Era. It is divided into three geologic periods that include the Paleogene, Neogene and Quaternary.

新生代：显生宙的第三个代，约从6500万年前至今。在这个时期地壳有强烈的造山运动，中生代的爬行动物绝迹，哺乳动物繁盛，生物达到高度发展阶段，和现代接近。后期有人类出现。通常可细分为古近纪，新近纪和第四纪。常考的概念主要是第四纪中的更新世和全新世。

Pleistocene & Holocene: The Quaternary Period is the current geologic period of the Cenozoic Era. The Quaternary Period is subdivided into the Pleistocene and Holocene Epochs. The Pleistocene Epoch is defined by repeated periods of glaciation. During this time intense periods of glaciation lasting up to 100,000 years, alternated with warmer interglacial periods of 20,000 to 30,000 years. Continental glaciers during this time reached latitudes as far as 40 degrees. Many large mammals that flourished during this time went extinct at the end of the Pleistocene around 11,700 years ago. The Holocene or present epoch represents an interglacial period. Fossils recognizable as human appear during the Quaternary Period.

更新世&全新世：第四纪是新生代的一个纪，包括更新世和全新世。更新世是冰川作用活跃的时期，在此期间发生了一系列冰川期和间冰川期气候回旋。地球上环境相对来说比较恶劣，所以当时地球上的物种，也进入了缓慢的增长期。进入全新世后，气候转暖，海面迅速上升，各种植物和动物开始繁荣。全新世是地质时代阶段，开始于12000～10000年前持续至今。哺乳动物的进化在此阶段最为明显，而人类的出现与进化则更是第四纪最重要的事件之一。