地球的形成,发育经历了漫长的地质岁月,距今大约已有46亿年。地球形成、发育的全部历史过程中称为地球史。在地学中地球史被分为五个大的地质时代,即太古代、元古代、古生代、中生代、新生代,代又分为纪。地球在其形成、发育过程中,后生成的地层,总是覆盖在先生成的地层上。先生成的地层,比后生成的 The formation and development of the Earth have experienced a long geological period, about 4.6 billion years ago. Earth’s history and development throughout the history of the process known as the Earth’s history. In earth science, earth history is divided into five major geological times, that is, the ancient, the ancient Proterozoic, Paleozoic, Mesozoic, Cenozoic, generation is divided into discipline. The formation of the Earth during its formation, development, after the formation of the formation, always covered in the formation of gentlemen. The strata that Mr. Cheng made were later than those generated