(i) How old is the earth? (ii) Describe the earth before man existed (iii) Why was there no life on earth?
Answers
The Earth formed more than 4 billion years ago along with the other planets in our solar system.
The early Earth had no ozone layer and was probably very hot. The early Earth also had no free oxygen.
Without an oxygen atmosphere very few things could live on the early Earth. Anaerobic bacteria were probably the first living things on Earth.
The early Earth had no oceans and was frequently hit with meteorites and asteroids. There were also frequent volcanic eruptions. Volcanic eruptions released water vapor that eventually cooled to form the oceans.
The atmosphere slowly became more oxygen-rich as solar radiation split water molecules and cyanobacteria began the process of photosynthesis. Eventually the atmosphere became like it is today and rich in oxygen.
The first complex organisms on Earth first developed about 2 billion years ago.