10 Events in Earth's History
By: Siobhan Miller
1. First Oceans Form
Around 4.2 to 3.8 billion years ago, the gaseous planet Earth cooled below 100 degrees Celsius. Causing the water to condense and pour down on the land as rain.
2. Bacteria Forms
3.5 billion years ago tiny single cells form they are the first forms of bacteria. They formed in newly formed oceans. And later introduced oxygen into the atmosphere around 2.7 billion years ago.
3. Organisms Move To Land
The evolution of marine life to land life consist of their fins turning into strong front limbs and weak back limbs. After the evolution most of the land life were amphibians and spiders, this happened 2 billion years ago.
4. Multi-cellular Organisms Appear
Single-celled organisms reproduce whenever the surrounding environment is right, the new multi-cellular algae began controlling exactly how many daughter cells they produce. Multi-cellular organisms formed 1 billion years ago.
5. Supercontinent Rodinia Forms
1billion years ago fragments of continental crust, pushed together by plate tectonic motion, began to assemble a giant continent scientists call Rodinia.
6. Cambrian Explosion
Also known as the "explosion of life", the cambrian explosion was an explosion of diversity in huge numbers of complex and multi-celled organisms that happened 530 million years ago.
7. Land Plants Evolve
420 million years ago the early plants evolved from aquatic environments, where they existed and diversified. From one group of these organisms probably the most common form is green algae. From this branch arose four groups of land plants, including the mosses, the ferns, the conifers, and the flowering plants.
8. Permian Mass Extinction
248 million years ago, Pangea stretched to the North and to the South poles causing extreme hot and dry conditions. Volcanoes began to form and gas began to rise, causing plants and organisms to die out. Causing an estimated extinction of 93-97% of all species.
9. The Cretaceous-Tertiary Mass Extinction
Many theories are out there regarding what caused the extinction of the dinosaurs, but the most widely accepted theory is the asteroid impact. Gases rise and sea levels decrease, causing an estimated extinction of estimated 71-81% of all species. Happening 65 million years ago.
10. Early Hominids Evolve
3.2 million years ago ape like creatures evolve into the earliest known hominids.