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See what shapes the planet...
Planets
Different planetary bodies have different interior structure, and some of these differences can be manifested on the surface of the planet. During planetary formation, the planet undergoes differentiation, where heavier elements `sink' towards the center, creating layers within the planet with different charac- teristics. Most rocky planets are composed of layers; a core, a mantle and a crustal surface.
Inside rocky planets the hot mantle convects, bringing heat to the sur- face of the planet, and the nature of the convection is manifested in the appearance of the lithosphere (the outermost layer of the planet). The lithosphere can be a single, solid rigid layer as on Mars (which results in stagnant lid convection), or it can be divided into mobile segments, as on Earth, in which case mantle convection manifests as plate tectonics (a class of mobile- lid convection). There is also a transitional state between stagnant-lid and mobile surface convection, referred to as episodic mantle convection, where the lithosphere is comprised of a single rigid surface for long periods before foundering and being overturned and replaced with newer/younger mantle material. Evidence of long-lived, ongoing plate motion on the Earth appears in the magnetic field of the sea oor, sea oor spreading, in the occurrence of earthquakes and even in the appearance of volcano locations.
What do we see under the surface?
Tectonics
Differences in internal planetary structure manifests itself on the surface of the planet. Rocky planets, like Earth, Mars and Venus, have similar structure, with a core, mantle and crust. Inside rocky planets the hot mantle convects, bringing heat to the surface of the planet, and the nature of the convection is manifested in the appear- ance of the lithosphere. The lithosphere can be a single, solid rigid layer as on Mars (which results in stagnant lid convection), or it can be divided into mobile segments, as on Earth, in which case mantle convection manifests as plate tectonics (a class of mobile-lid convection). There are also transi- tional states between stagnant-lid and mobile surface convection, referred to as sluggish-lid and episodic mantle convection, where in the latter, the litho- sphere is comprised of a single rigid surface for long periods before foundering and being overturned and replaced with newer/younger mantle material.
What happens when it goes wrong?
Hazards
The study of the internal structure, composition and dynamics of a planet is important to understand the manifestation of processes on the surface. They manifest as volcanoes, earthquakes and even landslides. These surface events are therefore hazards to humans. Understanding how they occur and how we can predict them are important for helping save lives. Earthquakes and volcanoes occur along plate boundaries on Earth. The Pacific plate (the largest plate), is currently subducting in the north, leading to what is referred to as the “ring of fire”. Volcanoes and large earthquakes occur all along the northern plate boundary.