Formation of the Earth

Formation of Earth

• Earth formed approximately 4.6 billion years ago from the solar nebula, a spinning disk of gas and dust.
• The solar nebula was created due to a shockwave from a nearby supernova which caused a dense cloud of dust and gas to collapse.
• The Sun formed first, condensing from about 99% of the matter in the nebula, primarily hydrogen, which then fused into helium, releasing massive energy.
• The Sun constitutes 99% of the solar system's total mass; the remaining mass formed other celestial bodies.
• Heavier elements like metals moved toward the Sun, while lighter gases were pushed outward.
• Formed planetesimals were solid structures within the early solar system that gradually collided and combined to create planets.
• The Giant-Impact hypothesis explains the Moon's formation: a Mars-sized planetesimal collided with early Earth, causing debris to form the Moon.
• During the Hadean Eon, Earth was a molten mass; it took 10-20 million years to reach its current size, and roughly 500 million years to cool enough for oceans to form.

Theories of Earth's Formation

• The core accretion model proposes that planets formed through collisions of solid materials in the solar nebula.
• This model faces challenges regarding the timing of gas giant formations.
• The disk instability model suggests planets formed from clumps of gas and dust, with heavier materials forming the core and lighter gases remaining in planetary atmospheres.
• A combination of both models may more accurately explain the planet formation process in our solar system.

Earth's Layers

• Earth cooled into three layers: core, mantle, and crust based on material density.
• The core consists of an inner core (solid) and outer core (liquid) made primarily of iron and nickel.
• The mantle is around 84% of Earth's mass, containing heavy silicates in a liquid state.
• The outer crust is a thin solid layer, composed of tectonic plates that move over the mantle, leading to geological activity like earthquakes.

Formation of Water and Atmosphere

• Volcanoes released gas and water vapor in a process called "degassing" as Earth cooled.
• Water and gases were derived from the solar nebula and meteorite impacts.
• Earth's position in the "Goldilocks zone" allowed for liquid water to exist.
• As the planet cooled sufficiently, water vapor condensed and formed ancient seas.
• The early atmosphere, rich in carbon dioxide, ammonia, and nitrogen, resembled that of present-day Venus.
• Cyanobacteria emerged, converting carbon dioxide into oxygen through photosynthesis, establishing an oxygen-rich atmosphere.

Formation of Land

• The crust is divided into tectonic plates that float on the liquid mantle, leading to geological changes.
• Ancient tectonic activity was responsible for the formation of land, promoting elevation variations and ocean basins.
• As Earth cooled, volcanic eruptions created islands and mountain ranges, shaping the planet's topography over time.

Explore the fascinating process of how the Earth formed 4.6 billion years ago from the solar nebula. Learn about the solar system's origin, its location in the Milky Way, and how life emerged on our planet. Test your knowledge on the formation of our home in the universe.