The Earth

Our beautiful Earth is the third planet of the System Solar, by order of distance from the Sun.

The blue planet is one of the four telluric planets (composed of rocks and metals - opposite of gaseous planets).

It is located at 150 millions of kilometers from the Sun ( 1 astronomic unit).

Some generalities:

Age: 4.54 billion years

Internal structure of Earth:

Formed over time, the Earth's structure consists of layers exhibiting unique physicochemical attributes. These strata are demarcated by boundaries (discontinuities) discerned through the investigation of seismic waves.

The general layers:

1. Crust : divided into continental and oceanic crust

2. Upper Mantle and 3. Lower Mantle: 84% of the earth's volume

4. Outer core: liquid, 4000°C (7232 °F)

5. Inner core: solid, 6000°C (10832 °F)

These layers are separated from each others by limits or transition zones called discontinuities. They were discovered in the XXth century thanks to the work on seismic waves. The three main seismic discontinuities are:

• Mohorovicic also called Moho: separates the trust from the mantle. Observed at a depth of 30 to 65 km (below oceanic crust or continental crust).

• Gutenberg: limit between the lower mantle and the outer core. At a depth of 2900km

• Lehmann: between the outer and inner core, at a depth of 5155km.

Did you know ? The deepest depth reached by cavers? 2 km (Georgia-EU) The deepest mine in the world? 3,5 km (South Africa) The deepest scientific drilling? 12,2 km (Russia)