evolution of earth
In the course of the past few billion years, Earth has endured numerous asteroid impacts, collisions with other celestial bodies, and periods of freezing. It is truly remarkable that our blue planet has managed to survive through all of these events, not to mention the reign of various extraordinary life forms. However, in order to embark on a comprehensive journey through the history of our planet, we must trace back to its origins approximately four and a half billion years ago. At that time, our solar system began to take shape from a dense cloud of interstellar gas and dust. This cloud eventually collapsed, forming a swirling disc of matter that grew increasingly hotter. Eventually, the fusion of hydrogen into helium gave birth to our sun, and simultaneously, the formation of baby Earth commenced. As our star came into existence, the matter located at the outer edges of the spinning disc began to coalesce, serving as the foundation for the planets and moons within our solar system. These clumps gradually accumulated more matter, resulting in their growth and transformation into spherical bodies. The clumps situated in the cooler regions of the solar system primarily consisted of ice, liquids, and gases, while the rocky materials closer to the Sun contributed to the formation of the inner planets, including Mars and Earth. During this early stage, Earth was incredibly active volcanically, emitting gases such as hydrogen sulfide, methane, and carbon dioxide. These gases constituted the initial atmosphere of our planet. Additionally, Earth was frequently bombarded by large asteroids and comets. However, a more significant collision occurred when Thea, a planet comparable in size to Mars, collided with our young Earth. This momentous event resulted in the ejection of matter into Earth's orbit, which subsequently coalesced under the influence of gravity, forming what we now know as the Moon. At this point in Earth's history, there were no oceans, as all water existed in the form of gas. However, approximately 3.8 billion years ago, our planet cooled sufficiently for water to condense and become liquid. This marked the emergence of the very first primitive ocean, transforming Earth into a water world. The presence of H2O, a vital ingredient for the creation of life, led to the appearance of living organisms on Earth around 3.7 billion years ago. These early life forms were primitive in nature Earth didn't remain a water world for long, as the emergence of the very first continents from the ancient ocean took place. These land masses, known as cratons, gradually rose from the ocean, leading to the formation of the initial supercontinent called Valbara. Although Valbara was relatively small, scientists believe it was even smaller than the continent of Australia.