Solar System and Earth Formation: A Deep Dive

Geology: Understanding Our Planet and Solar System

Geology is the science that studies the composition, structure, origin, and evolution of the Earth and other celestial bodies within the solar system.

Origin of the Solar System

The solar system, approximately 4.5 billion years old, originated from a nebula. This nebula consisted of dust, hydrogen, helium, and trace amounts of other chemical elements.

The nebula underwent several distinct phases:

1. Condensation: A nearby supernova explosion destabilized the initial nebula. Attractive forces overcame repulsive forces, causing materials to condense. The concentration was highest at the center, forming a protosun (primitive sun).
2. Planetesimal Formation: Condensed materials collided, forming planetesimals. These planetesimals eventually coalesced into planets and satellites.
3. Accretion: The sun initiated nuclear fusion reactions, releasing energy and creating the solar wind. This wind swept away remaining dust and gas, concluding the accretion phase.
4. Differentiation: Materials began to differentiate based on their chemical structure.

Formation of the Earth

Earth, also around 4.5 billion years old, went through similar stages. Over these years, Earth evolved, resulting in distinct layers: the atmosphere, the hydrosphere, and various internal layers, each named differently depending on the geological model.

Earth's Characteristics

• Earth is a geoid-shaped planet.
• The acceleration due to gravity is approximately 9.8 m/s².
• Water covers roughly three-quarters of its surface.
• Its equatorial radius is 6,378 km, and its polar radius is about 21 km less.
• Earth has two translational motions and one rotational motion.
• Its mass is approximately 6 x 10²⁴ kg.
• The average surface temperature is around 15°C.

Early Earth Development

Initially, Earth's temperature reached 2,000°C due to collisions between planetesimals, meteorites, and energy released by radioactive elements.

The Earth's mass consisted of molten rocks (plutonic), primarily peridotite, and liquid iron. As the peridotite solidified, iron migrated towards the core.

High temperatures caused the planet to degas, forming the early atmosphere. This primitive atmosphere was composed of CO₂, H₂O, CH₄, NH₃, rare gases, and hydrogen and helium (the latter two were lost due to low gravity).

Today, Earth's atmosphere primarily consists of nitrogen (78%), oxygen (20.9%), argon (0.9%), and trace amounts of CO₂, krypton, xenon, and neon.