Earth's Origin and Internal Structure

Study Notes

The Solar System, including the Sun and planets, formed from a solar nebula, which also formed the "Proto-Earth".
The nebular material in Proto-Earth was uniform, with no stratification.
Meteors and asteroids impacted Proto-Earth, causing gravitational compression.
As the Earth cooled and coalesced, heavier materials like iron and nickel migrated to the center, while lighter materials like silicon, oxygen, aluminum, and potassium remained near the surface, resulting in a density-stratified planet.

By drilling into the Earth's deep, with the deepest hole being about 12 km (less than 0.2% of the distance from the surface to the center).
By studying and measuring the travel times of earthquake waves to seismograph stations.
Earthquake waves are categorized into two types: Surface waves, which travel near the surface, and Body waves, which travel deep into the Earth.

There are two types of body waves: P-waves (Primary waves) and S-waves (Secondary waves).
P-waves are compressional waves that are the fastest of seismic waves, can move through solid rock and fluids, and travel horizontally through a medium by compression and dilation.
S-waves are slower than P-waves, can only move through solid rock, and move rock particles up and down or side-to-side, perpendicular to the direction of travel.

Continental Crust: 35 km thick, up to 75 km thick under mountains, and composed of felsic (Si-rich) to mafic (Fe-Mg rich) materials.
Oceanic Crust: thinner and denser than Continental Crust.