You are the lucky student of a wacky professor who develops a time machine. He asks if you will test it with him. You get in and there is an immediate glitch–the date readout fails so that when you land you are not sure what era you are in. As your time machine lands, you see an unusual landscape before you. As you open the door you realize you cannot breathe. You quickly shut the door, realizing you are in the _____.
1) Archaean eon
2) Cambrian period
3) Cenozoic era
4) Mesozoic era

You are in the Archean Eon era because the it was early in the Archean that life first appeared on Earth. The most two earlier of the formal divisions of Precambrian time (about 4.6 billion to 541 million years ago) and the period when life first formed on Earth It began about 4 billion years ago with the formation of Earth’s crust and enlongated to the begining of the Proterozoic Eon 2.5 billion years ago; the latter is the second formal division of Precambrian time.

In the Archean eon there are unsual landscapes no rocks are preserved from this stage. The earliest terrestrial materials are not rocks but minerals.

Throughout the Archean, oceanic and island arc crust was produced semi-half way.

You cannot breathe because there was no oxygen on the Earth. Oxygen was only present in compounds such as water and chemical reactions change to carbon containing molecules that form simple living cells that does not require oxygen.