Planetary geology is the study of the surface and core (geological) composition and variation of planetary objects. It is essentially just an extension of geology (the study of the Earth) to other planets. Our terrestrial planets formed through a process called accretion, which occurs when smaller objects gather together to make larger ones. This causes a somewhat uniform ‘pattern’ between our terrestrial planets in makeup.
Planetary Makeup
Terrestrial are split into three main layers:
- The high density core region at the center of a planet
- The rocky mantle layer between a planet’s core and crust
- The outermost crust or surface layer of a planet.
In a planet’s core, the convection and conduction contribute to ongoing and already-undergone differentiation— gravity has separated materials in the core by density already, with higher-density materials sinking down and making the deepest layers whilst lower-density materials are pushed to the top.
The term lithosphere refers to both the crust and the upper mantle of a planet. It can be used to describe the change in the surface of Earth due to geological activity, which is any change to the planet’s surface after its initial formation. Geological activity can manifest in many forms, but most prominent are events like volcanic eruptions that create new surface, and earthquakes that can break up existing surface and cause other terraforming events like tsunamis due to the effects of their seismic waves.