What is the history of Earth? (1)

The history of Earth spans over 4.5 billion years and is divided into several distinct geological eons, eras, and periods, each marked by significant events that shaped the planet’s physical and biological development.

1. Formation (Hadean Eon: 4.5 – 4.0 billion years ago)

• Formation of Earth: Earth formed about 4.5 billion years ago from the dust and gas surrounding the young Sun. It began as a molten mass of rock and metal.
• Moon Formation: The Moon likely formed shortly after Earth in a massive collision between the young Earth and a Mars-sized object.
• Atmosphere and Oceans: Early Earth had a toxic atmosphere composed of hydrogen, methane, and ammonia. Eventually, as the planet cooled, water vapor condensed to form the oceans.

2. Archean Eon (4.0 – 2.5 billion years ago)

• First Life: The earliest evidence of life appeared in the form of single-celled organisms, likely extremophiles living in harsh environments such as volcanic vents. These early life forms were prokaryotic microbes.
• Photosynthesis Begins: Cyanobacteria (blue-green algae) developed the ability to photosynthesize, releasing oxygen as a byproduct. This process began the gradual accumulation of oxygen in Earth’s atmosphere.

3. Proterozoic Eon (2.5 billion – 541 million years ago)

• Great Oxygenation Event: Around 2.4 billion years ago, oxygen levels increased dramatically due to photosynthesis, leading to the extinction of many anaerobic organisms but paving the way for more complex life.
• Formation of Supercontinents: During this eon, Earth’s continents began to coalesce into supercontinents, including Rodinia and Pannotia.
• First Eukaryotic Cells: Eukaryotes, cells with nuclei, evolved, giving rise to more complex organisms, such as algae, and eventually leading to multicellular life.

(To be continued)