4.6 Billion years ago, in the Hadien eon

The start of the timeline of Earth from when Earth was born up to today started by the formation of the Earth. The earth formed 4.6 billion years ago in the Hadien eon, after our solar system formed. It formed when lots of dust and rocks started clumping together and formed a big rock, big enough to start pulling in other rocks around it because of gravity. After lots more dust and rocks started getting pulled around the big rock, it formed a big spherical shape, creating the earth.

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4.6 Billion years ago, in the Hadien eon

The chronology of Earth, from when Earth was born to today, started back when the Earth first formed. The earth formed 4.6 billion years ago in the Hadien eon, after our solar system formed. It formed when lots of dust and rocks started clumping together and formed a big rock, big enough to start pulling in other rocks around it due to gravitational pull. After lots more dust and matter started getting pulled around the big rock, it formed a big spherical shape, creating the earth. Scientists know how old the Earth is, by studying the rock layers of the Earth, and by comparing how old the layers are with each other. This event is important to life because if Earth never formed, we wouldn’t be here, nor any other life that is on Earth today, would exist either.

4.5 Billion years ago, in the Hadien eon

4.5 Billion years ago, in the Hadien eon, a planet-sized rock, named Theia, collided with the Earth. After this collision happened, all the floating particles and matter from the collision clumped together and kept getting bigger and bigger. Then, because of gravitational pull, the rock started pulling in more and more matter and dust, which later formed a spherical shape, created the moon.

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4.5 Billion years ago, in the Hadien eon

4.5 Billion years ago, in the Hadien eon, a planet-sized rock, named Theia, collided with the Earth. After this happened, all the floating particles from that collision clumped together and kept getting bigger and bigger. Then, because of gravity, the rock started pulling in more and more matter and dust, which later created the moon. Because of the gravitational pull from the moon, the earth has a tilt, which allows the Earth to have seasons, and to contain a normal temperature for life to be able to survive. Scientists know how old the moon is, by studying rocks on the moon, moon samples and meteorites that crashed on the moon, and by finding out how old they are to find out how old the moon is. This event is important because, without the moon, the Earth wouldn’t have a tilt, since the Earth is tilted due to the gravitational pull of the moon. Because of this, the Earth's weather would be very extreme, and could even have ice ages. We could not have any seasons either without the moon. If the Earth was constantly facing ice ages, it would be really hard for life to survive on Earth.

3.8 Billion years ago, in the early Archean Eon

3.8 Billion years ago in the early Archean eon, the earth started cooling down, and all the water vapor from the earth's atmosphere condensed and formed oceans. At this time, the earth was still being bombarded by comets and asteroids. Scientists believe that most of the water we have today, was brought to us by asteroids and comets. When the asteroids were crashing onto earth, they contained water crystals inside of them, which when they hit the earth, they would release water on to the earth. The earth had cooled down more, enough to almost be able to sustain life. But, the earth still did not have any life at this time, as the earth was just starting to cool down.

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3.8 Billion years ago, in the early Archean Eon

3.8 Billion years ago in the early Archean eon, the earth started cooling down, and all the water vapor from the earth's atmosphere condensed and formed oceans. At this time, the earth was still being bombarded by comets and asteroids. Scientists believe that most of the water we have today was brought to us by asteroids and comets. When the asteroids crashed onto earth, they contained water crystals inside of them, which when they hit the earth, they would release water onto the earth. The earth had cooled down more at this time. A Canadian geologist, Sherwood Loller, found water at a depth 3 kilometers deep, which was found to be between 1.5 billion and 2.64 billion years old. This proves that water had existed at that time. This event is important, because one element that life needed to be able to exist, was liquid water. So, if this event did not ever happen, life would have never been able to exist on Earth, which means we wouldn’t be able to be here today.

3.7 Billion years ago, in the early Archean Eon

3.7 Billion years ago in the early Archean eon, the first microbes appeared on Earth! Microbes are living beings made of 1 cell. Scientists have found evidence of them in rocks. Scientists have many theories on how the origin of life first came to Earth, but no one really knows the real reason why life first came to Earth. One theory scientists have on how the origin of life started is that, after asteroids released water from them, the asteroids also started to release their minerals onto the water. Then, those minerals and water joined together to create life. There are many other theories on the origin of life, this is just one of them. At this time, there were many one-celled microbes in the waters on Earth. The first life on Earth was unicellular, which meant they were only made of one cell. They were prokaryotes, meaning that these cells did not have any nucleus in them. Basically, life was not as complicated at that time, as it is today. These microbes were only made of one cell. They could grow and develop, reproduce, react to their environment, and maintain a stable environment inside of them, they had a complicated chemistry, and they were made of 1 cell, which meant they were so small, that humans would not have been able to see them without a microscope. They had characteristics of any living being. These unicellular organisms created all of the life we know of today.

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3.7 Billion years ago, in the early Archean Eon

3.7 Billion years ago in the early Archean eon, the first microbes appeared on Earth! Microbes are living beings made of 1 cell. Scientists have found evidence of them in rocks. Scientists have many theories on how the origin of life first came to Earth, but no one knows the real reason why life first came to Earth. One theory scientists have on how the origin of life started is that, after asteroids released water from them, the asteroids also started to release their minerals onto the water. Then, those minerals and water joined together to create life. There are many other theories on the origin of life, this is just one of them. At this time, there were many one-celled microbes in the waters on Earth. Earth's first life was unicellular, meaning they were only made of one cell. They were prokaryotes, meaning that these cells did not have any nucleus in them. Basically, life was not as complicated at that time, as it is today. These microbes were only made of one cell. They could grow and develop, reproduce, react to their environment, and maintain a stable environment inside of them, they had a complicated chemistry, and they were made of 1 cell, which meant they were so small, that humans would not have been able to see them without a microscope. They had characteristics of any living being. These unicellular organisms created all of the life we know of today. According to NASA, the earliest known fossils date back to 3.5 billion years ago, and there is evidence that biological activity took place earlier than that, which proves that life existed back then, which is how scientists know that life existed back then on Earth. This event is important because, if the first microbes never appeared on Earth, no humans, animals, plants, no life would exist on Earth.

2.4 Billion years ago, in the early Proterozoic eon, Paleoproterozoic era

2.4 Billion years ago, in the early Proterozoic eon, Paleoproterozoic era, a type of bacteria named Cyanobacteria evolved, and started the process of photosynthesis to create oxygen for the first time on Earth. Photosynthesis is a process that functions when life takes in energy from the sunlight and creates oxygen with it. This type of bacteria evolved from the regular microbes that first appeared, through mutations. Mutations are when a living creature gives birth, but the DNA of the baby slightly changes, and is different in some way, from the DNA of the creature that gave birth. Because of mutations, the baby could look different from its parents too. The original regular microbes mutated and mutated due to the change of the environment on Earth, and evolved into Cyanobacteria.

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2.4 Billion years ago, in the early Proterozoic eon, Paleoproterozoic era

2.4 Billion years ago, in the early Proterozoic eon, Paleoproterozoic era, a type of bacteria named Cyanobacteria evolved, and started the process of photosynthesis to create oxygen for the first time on Earth. Photosynthesis is a process that functions when life takes in energy from the sunlight and creates oxygen with it. This type of bacteria evolved from the regular microbes that first appeared, through mutations. Mutations are when a living creature gives birth, but the DNA of the baby slightly changes, and is different in some way, from the DNA of the creature that gave birth. Because of mutations, the baby could look different from its parents too. The original regular microbes mutated and mutated due to the change of the environment on Earth, and evolved into Cyanobacteria.

Scientists have used geochemical tools to look for oxidized elements in ancient rocks that have found hints that oxygen was present at this time. Scientists have also found fossils of cyanobacteria, and learned that they were similar to the modern cyanobacteria (blue-green algae) we have today. Scientists have also found out that some cyanobacteria at that time did not have the genes to photosynthesize, meaning that most cyanobacteria learned how to photosynthesize later in their life. They also discovered that cyanobacteria could share the ability of photosynthesizing with eachother, and lastly, scientists have found a small cyanobacterium that lived in a plant without the tubes for moving water, which helped them figure out when cyanobacteria started photosynthesizing. This is how scientists figured out that cyanobacteria were the ones that started photosynthesizing, and how they photosynthesized.

2.4 Billion years ago, in the early Proterozoic eon, Paleoproterozoic era

2.4 Billion years ago in the early Proterozoic eon, Paleoproterozoic era, after cyanobacteria created oxygen and let it into the earths atmosphere, some living beings benefitted and evolved from the oxygen, while others could not handle the oxygen, this is because some living beings did not need any oxygen, but since there was oxygen constantly going inside them, they could not handle it and died. But some living beings evolved from the oxygen because the oxygen benefitted them in some way, or helped the living being adapt to the oxygen, causing it to mutate and change in some way.

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2.4 Billion years ago, in the early Proterozoic eon, Paleoproterozoic era

2.4 Billion years ago in the early Proterozoic eon, Paleoproterozoic era, after cyanobacteria created oxygen and let it into the earth's atmosphere, some living beings benefitted and evolved from the oxygen, while others could not handle the oxygen, this is because some living beings did not need any oxygen, but since there was oxygen constantly going inside them, they could not handle it and died. But some living beings evolved from the oxygen because it benefitted them in some way, or helped the living being adapt to the oxygen, causing it to mutate and change in some way.

Scientists have used geochemical tools to look for oxidized elements in ancient rocks that have found hints that oxygen was present at this time. This event is important because without this event occurring, animals from that time would not have been able to evolve. If those animals never evolved, then the animals we have today would have never come to be.

1.5 Billion years ago, in the Proterozoic eon, Neoproterozoic era

1.5 billion years ago in the Proterozoic eon, Neoproterozoic era, a long time after the Great Oxidation Event, now there is a lot of oxygen in the air. At this time, multicellular life became more apparent on Earth. Scientists believe that multicellular life could have started by endosymbiosis. Endosymbiosis is when one cell goes inside the other, and both cells benefit. The cell on the inside, produces energy, while the cell on the outside, protects both cells from predators. This process might have sparked the start of multicellular life.

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1.5 Billion years ago, in the Proterozoic eon, Neoproterozoic era

1.5 billion years ago in the Proterozoic eon, Neoproterozoic era, a long time after the Great Oxidation Event, now there is a lot of oxygen in the air. At this time, multicellular life became more apparent on Earth. Scientists believe that multicellular life could have started by endosymbiosis. Endosymbiosis is when one cell goes inside the other, and both cells benefit. The cell on the inside, produces energy, while the cell on the outside, protects both cells from predators. This process might have sparked the start of multicellular life. Scientists have found coil-shaped fossils that may have been blue-green algae, that were around 2 Billion years old, found in the US and Asia. Scientists have also found fossils of Grypania spilaris, which were tiny microscopic multicellular filaments, that may have been around 2.5 Billion years old in South Africa, which scientists say may have been the first sign of multicellular life on Earth. This is how scientists know about this event occurring. This event is important because, if multicellular life never evolved from unicellular microbes and never existed on Earth, humans, animals, plants, and every living being that we see today would not have been able to be here without multicellular life.

640 mya, in the Proterozoic eon, Neoproterozoic era

640 million years ago, in the Proterozoic eon, Neoproterozoic era, after sudden oxygen levels in the earth's atmosphere arose from the Great Oxidation Event, the earth slowly started becoming colder. A few billion years after the Great Oxidation Event, the Earth became a snowball and faced its first ice age. This event happened because before oxygen appeared on Earth, the Earth's atmosphere was full of methane, keeping the Earth warm. When oxygen levels increased in the earth's atmosphere, the methane levels went down, causing the earth to go into an ice age. During snowball Earth, life survived by finding warm spots under the ocean or adapting to the environment during snowball Earth.

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640 mya, in the Proterozoic eon, Neoproterozoic era

640 million years ago, in the Proterozoic eon, Neoproterozoic era, after sudden oxygen levels in the earth's atmosphere arose from the Great Oxidation Event, the earth slowly started becoming colder. A few billion years after the Great Oxidation Event, the Earth became a snowball and faced its first ice age. This event happened because before oxygen appeared on Earth, the Earth's atmosphere was full of methane, keeping the Earth warm. When oxygen levels increased in the earth's atmosphere, the methane levels went down, causing the earth to go into an ice age. During snowball Earth, life survived by finding warm spots under the ocean or adapting to the environment during snowball Earth. Scientists have found banded iron formation from that time in the oceans of Earth, which scientists say might have been caused by the ice layer from the snowball Earth. Scientists say that when a layer of ice covered the oceans of Earth, because of the layer of ice the oceans might have changed a lot, and become more rich in iron, which is how scientists know about snowball Earth. Snowball earth has been important to life, since because of Snowball Earth, is important because, at that time, life was able to adapt to colder temperatures and was able to evolve because of the sudden temperature drop in the earth's atmosphere. So, if this event did not occur on Earth, some animals would have probably looked different now, than it is today.

542 mya, in the Cambrian period, Palezoic era, phanerozoic eon, after the precambrian eon, Early Cambrian epoch

Before the Cambrian Explosion, there was no life on land. All developed life was mainly under the sea. At the beginning of the Cambrian, 542 Million years ago, there was an explosion of life under the seas, and no one knows what caused it. After the Cambrian Explosion, these slow, soft, boneless creatures evolved into fast hard-shelled creatures. Scientists believe that because of the boost of oxygen in the atmosphere from the Great Oxidation event, these soft-bodied creatures had slowly evolved into hard-shelled creatures, by adapting to the oxygen in the water. The slow soft-bodied creatures that had later evolved during the Cambrian actually did not have any bones. They were also mainly found on the seafloor and mainly survived by absorbing nutrients from the seawater itself. Scientists believe that these creatures are what gave diversity to most animals we know of today, by many processes of mutations by evolution and adaptation. The most famous creature from the Cambrian is the Trilobite, a small cockroach-like creature.

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542 mya, in the Cambrian period, Palezoic era, phanerozoic eon, after the precambrian eon, Early Cambrian epoch

Before the Cambrian Explosion, there was no life on land. All developed life was mainly under the sea. At the beginning of the Cambrian, 542 Million years ago, there was an explosion of life under the seas, and no one knows what caused it. After the Cambrian Explosion, these slow, soft, boneless creatures evolved into fast hard-shelled creatures. Scientists believe that because of the boost of oxygen in the atmosphere from the Great Oxidation event, these soft-bodied creatures had slowly evolved into hard-shelled creatures, by adapting to the oxygen in the water. The slow soft-bodied creatures that had later evolved during the Cambrian did not have any bones. They were also mainly found on the seafloor and mainly survived by absorbing nutrients from the seawater itself. Scientists believe that these creatures are what gave diversity to most animals we know of today, by many processes of mutations by evolution and adaptation. The most famous creature from the Cambrian is the Trilobite, a small cockroach-like creature. Scientists say that 500 million years ago most of the major animal groups we have today started showing up at the fossil records, suddenly. This was how scientists got to know about the Cambrian Explosion. This event is important to life because many marine animals we have today are either still here since the Cambrian explosion, or have evolved from the Cambrian explosion, like jellyfish. They have been here on Earth since the Cambrian explosion happened. But, if the Cambrian explosion never happened, then most of the marine animals we have today wouldn’t be here.

3.3 Billion years ago, in the early Archean Eon

3.3 Billion years ago in the early Archean Eon, the first continents started emerging from the oceans of Earth. These ancient lands that were emerging from the oceans were called Cretons. As more and more land arose from the ocean, the first supercontinent appeared. The name of this supercontinent was Vaalbara. Vaalbara was not big, as scientists believe that it was smaller than Australia. Vaalbara went through many processes to form. One process that formed Vaalbara was a process called continental drift. Continental drift is a process of how continents move on Earth. Large pieces of land on Earth, called continents, are actually floating on top of molten lava. Some times, these continents move and form together, and sometimes they break apart. That is called continental drift. When cretons started to mash together, they formed Vaalbara, and created the first super continent. Scientists have found 2 large cratons that had very similar rock structure, being from 3.5 Billion years old, to being 2.7 Billion years old. Cratons are pieces of ancient lands on earth. Scientists know how old the cretons are, by studying the rock layers of the cretons. Scientists have also found out that 3.87 billion years ago, these large cretons were possibly part of 1 big supercontinent, Vaalbara. This is how scientists know that Vaalbara existed. This event is important because, as Vaalbara formed and broke apart, life forms became separate from eachother, which caused many life forms to adapt to their new environments, causing evolution and creating new and diverse species.

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3.3 Billion years ago, in the early Archean Eon

3.3 Billion years ago in the early Archean Eon, the first continents started emerging from the oceans of Earth. These ancient lands that were emerging from the oceans were called Cretons. As more and more land arose from the ocean, the first supercontinent appeared. The name of this supercontinent was Vaalbara. Vaalbara was not big, as scientists believe that it was smaller than Australia. Vaalbara went through many processes to form. One process that formed Vaalbara was a process called continental drift. Continental drift is a process of how continents move on Earth. Large pieces of land on Earth, called continents, are actually floating on top of molten lava. Some times, these continents move and form together, and sometimes they break apart. That is called continental drift. When cretons started to mash together, they formed Vaalbara, and created the first super continent. Scientists have found 2 large cratons that had very similar rock structure, being from 3.5 Billion years old, to being 2.7 Billion years old. Cratons are pieces of ancient lands on earth. Scientists know how old the cretons are, by studying the rock layers of the cretons. Scientists have also found out that 3.87 billion years ago, these large cretons were possibly part of 1 big supercontinent, Vaalbara. This is how scientists know that Vaalbara existed. This event is important because, as Vaalbara formed and broke apart, life forms became separate from eachother, which caused many life forms to adapt to their new environments, causing evolution and creating new and diverse species.

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