Earth's 10 Most Important Events

4.5 billion years ago Earth was created.

This was cause by accretion and giant impacts of other planetesimal.

3.5 billion year ago was the first bacterial and archean life on Earth.

Some scientists believe that this happened earlier.

2 billion years ago was the Great Oxidation Event that allowed the ozone layer to form.

This protected life on Earth from ultraviolet radiation.

1.25 billion years ago stromatolites, mats of bacteria, reach their peak.

This cause the oxygen levels in the atmosphere to rise.

1 billion years ago multi-celled organisms appear.

This increases the complexity of organisms on Earth.

1 billion years ago the Supercontinent Rodinia forms.

This lasted for 450 million years.

750 million years ago the Earth was covered from pole to pole with glaciers.

As a result of this, Earth's temperature was much cooler.

530 million years ago the Cambrian Explosion begins.

This was the rapid appearance of most major animal groups.

248 million years ago the Permian Extinction happened.

This wiped out 96% of all species on Earth.

240 million years ago was when the earliest dinosaurs lived.

These were only 2-3 feet tall.

200,000 years ago modern humans evolved.

This is the most recent event on the geologic time scale.