_{Zircon forms in the tetragonal system. It can be colorless to yellow, orange, brown, pink, red, green, and blue. These colors are caused by rare, radioactive elements in stages of radioactive breakdown. It was formed 4.4 bya.}

_{It was found near the Acasta River. It is a very important rock because it contains fragments of the oldest known crust and is recorded to have more than a billion years of magmatism and metamorphism. It was formed 4.03 bya.}

_{The first living organisms on earth, like microscopic bacteria, were found in the oceans. It was formed 3.5 bya.}

_{The early tectonic plates began to move, which created the first rift valleys and geologic features. It started 4 bya.}

_{There is proof that Oxford, Ohio was once part of an inland sea that stretched to the Gulf of Mexico to the Arctic. It was also full of marine life at one point. This was 450 mya.}

_{This was the initial squeeze of the margin of North America. This occured 470 mya.}

_{A major geological collision that created the pangea. This happened 320 mya.}

_{It is the most severe extinct event. It was very invasive and killed off most things. This happened 252 mya.}

_{The First fossil that was found of dinosaurs was in Cornwell, Oxfordshire, Uk. Dinosaur fossils have now been found on all 7 continents of the earth. They formed 165 mya.}

_{The Earth moved into separate continents over time due to tectonic plate motion. This occured 200 mya.}

_{It happened in Antarctica, southern South America, southern Africa, India, and Australia.}

_{The Laramide Orogeny (mountain building event) uplifted the Rocky Mountains. This caused a lot of events afterwards, like extensive volcanic ash falls and mudflows. This happened 75 mya.}

_{It was formed mostly because of the breakup of the supercontinent pangea. It was formed about 180 mya.}

_{Toba supervolcano - an ancient volcanic eruption. Around 10,000 individuals survived this. This happened 74,000 years ago.}

_{30 meter-diameter asteroid/comet. This explosion knocked down approximately 80 million trees over an area that was 2,150 square kilometers. This occured in 1908 (117 years ago).}

_{This is the oldest found fossil of a female skeleton. It was formed 4.4 mya.}

_{Stone tools, figurines, and wooden structures were found. They seem human-made and act as some tools we now have today. They were created 3.3 mya.}