The geologic time scale was created through a combination of observations, fossil records, and the study of rock layers and isotopes. Scientists used various methods, including radiometric dating, to determine the ages of rocks and fossils. They also examined the presence or absence of certain fossilized organisms to establish different time periods.
The scale is organized into four major divisions called eons: Hadean, Archean, Proterozoic, and Phanerozoic. The Phanerozoic eon is further divided into eras, including the Paleozoic, Mesozoic, and Cenozoic eras. These eras are then subdivided into periods, such as the Cambrian, Jurassic, and Pleistocene periods.
During Precambrian time, the Earth's environment underwent significant changes. Processes such as the formation of oceans, the development of the atmosphere, volcanic activity, and the emergence of life forms influenced the environment. The formation of the first continents and the eventual rise of oxygen levels due to photosynthetic organisms also had a profound impact on shaping the Earth's environment during this time.
Think about how the geologic time scale was created and how it is divided. Then answer the following questions.
• How did scientists form the geologic time scale?
• How is this scale organized?
• What processes changed the Earth's environment during Precambrian time?
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Scientists formed the geologic time scale by combining observations of rock layers and fossil records, using various dating methods. The scale is organized into eons, eras, and periods to represent different time intervals in Earth's history. The Precambrian time was marked by the formation of oceans, the development of the atmosphere, volcanic activity, the emergence of life forms, and the formation of the first continents.
1 answer