Geologic Timeline Reflection

The first major event in Earth's history was the cyanobacteria oxygenating the atmosphere. This radically changed the composition of Earth's atmosphere and is the reason most current life exists. There was a mass extinction event that killed off the obligate anaerobes. This probably caused life on land to appear. This also allowed stimulated evolution to survive in oxygen rich environments. The next most event in Earth's history was the Permian extinction event. This was the deadliest mass extinction event in Earth's history killing 90% of marine organisms and 70% of terrestrial organisms. It is speculated that it was caused by an eruption or release of gas from the ocean. It ended the paleozoic era and made way for the mesozoic era. It took 30 million years for life recover and there is a gap in the fossil record because of the event. The last major event was the Cretaceous mass extinction. It was the last mass extinction and well known for ending the dinosaurs and mesozoic era. A giant meteorite crashed onto Earth's surface killing three quarters of all life on Earth. It is very important because it ended the dinosaurs and let mammals take over which would eventually give rise to humans. The scale of Earth's history is impressive and makes you realize how insignificant you are in a grander scale. I was surprised that  the Precambrian lasted so long and that we have a lot of blanks for information on the Precambrian. The Precambrian stretched most of the room while the rest could fit on a table. Many scientists say we are in the middle of the 6th mass extinction event because our killing of species through deforestation is killing many species. Many mass extinctions take thousands of years and if we don't change, we could be the cause of a mass extinction that will probably lead to the end of humans. I want to know more about the early Precambrian and how life formed because it seems strange how such complicated life could come from random assortment of chemicals. click here for picture