ASBOG Practice Exam

List the eons from youngest to oldest. Which is the correct order?

1. Hadean; Archean; Proterozoic; Phanerzoic

2. Proterozoic; Archean; Hadean; Phanerzoic

3. Phanerzoic; Proterozoic; Archean; Hadean

4. Archean; Hadean; Phanerzoic; Proterozoic

The correct answer is: Phanerzoic; Proterozoic; Archean; Hadean

The correct order from youngest to oldest is indeed Phanerzoic, Proterozoic, Archean, and Hadean. Phanerzoic eon is the most recent, spanning from approximately 541 million years ago to the present. It is characterized by the abundance of life forms and includes the development of complex multicellular organisms. Following this is the Proterozoic eon, which lasted from about 2.5 billion years ago to 541 million years ago. This eon saw significant geological and biological developments, including the buildup of atmospheric oxygen and the emergence of early multicellular life. Next in line is the Archean eon, which ranges from about 4 billion to 2.5 billion years ago. This eon is notable for the formation of the Earth's first stable continental crust and the emergence of the first known life forms, primarily prokaryotic microorganisms. At the oldest end is the Hadean eon, which dates from the formation of the Earth about 4.6 billion years ago to approximately 4 billion years ago. This eon was characterized by extreme conditions, such as molten surfaces and intense volcanic activity, with no known life forms present. This ordering reflects the geological