The Geologic Time Scale is a huge record of earth history. Recording all the big geologic events like evolution and mass extinction. The Earth is 4.6 billion years old.
Scientist create the geologic time scale by looking at different fossil records,layers of rock. They had to record the age of the rock with radioactive dating. Radioactive dating helps find the absolute age of something. But before the had radioactive dating they had to put fossil records in order by relative age by index fossils.
The scientists also had to figure out when one Eras ended. They use big geologic events like mass extinction and major changes in life forms. They also use when an animal starts to dominate over the others.
Scientist create the geologic time scale by looking at different fossil records,layers of rock. They had to record the age of the rock with radioactive dating. Radioactive dating helps find the absolute age of something. But before the had radioactive dating they had to put fossil records in order by relative age by index fossils.
The scientists also had to figure out when one Eras ended. They use big geologic events like mass extinction and major changes in life forms. They also use when an animal starts to dominate over the others.