Definition
Earth is a rocky planetary body composed of mineral, fluid and gaseous substances forming a coherent whole. Its surface and internal envelopes generate diverse environments in constant interaction.
Internal structure
The interior is organized into a metallic core, a ductile silicate mantle and a solid crust. Transitions between these regions show variations in density, plasticity and thermal conductivity that structure internal movements.
Fluid envelopes
Around the solid surface lie the hydrosphere—composed of liquid, solid or vaporized water—and the atmosphere made of stratified gases. These envelopes regulate the energetic exchanges between the interior and the external environment.
Surface and dynamics
The surface displays continents, oceanic basins, relief zones, plains and fracture lines. Internal motions cause deformations, material formation and the progressive reshaping of the topography.
Geophysical systems
The system includes a magnetic field generated by core motions, a structured atmospheric circulation, a water cycle linking ocean, surface and atmosphere, and a set of processes regulating the energetic balance.
Evolution
The internal layers cool and reorganize over time, the surface changes under the action of fluids, and the gaseous envelopes evolve according to internal exchanges and external radiation.
Boundaries and interactions
The main boundary is the transition to surrounding space, where gases become rarefied. Interaction with the space environment influences the shape of the atmosphere, energetic dynamics and the transfer of particles.