SafekipediaLid tectonics, also called stagnant lid tectonics or single lid tectonics, is a process that scientists think happens on some planets and moons in our Solar System. It might have been on Earth when it was very young. In lid tectonics, the surface, called the lid, is made of solid silicate minerals and does not move much.
This is different from plate tectonics, where Earth's surface moves around a lot. The stagnant lid sits above a layer called the mantle that moves, but the lid itself stays mostly still. This kind of tectonics has much less movement than plate tectonics.
Scientists think that early Earth might have had a stagnant lid before it changed to the moving plates we see today. This change probably happened a long time ago during a time called the Archean epoch. Learning about lid tectonics helps us understand how planets and moons, including Earth, change over very long periods of time.
Formation
A lid tectonic regime happens when the outer layer of a planet, called the lithosphere, is too stiff to move with the mantle underneath. This stiff layer, or "lid," does not break easily. Whether the planet has stagnant lid tectonics depends on how strong the lithosphere is compared to the movements in the mantle. If the lithosphere is stronger, then there is much less movement of the planet's surface.
Main article: Yield strength
Factors contributing to lid tectonics
Many things affect whether lid tectonics happens on a planet or moon. The temperature near the center and the presence of water are important.
The solid outer layer, called the lid, does not move with the softer layers below it. Near where the lid touches the softer material, melted rock can form and drip down. This keeps the lid still and stops it from mixing the layers below very much.
Other planetary bodies
Stagnant lid tectonics is the most common type of tectonic activity in our Solar System. Planets like Mercury, the Moon, Venus, and Io are thought to have had this type of tectonics for a very long time.
On Mercury and the Moon, heat escapes mainly by moving through the lid. This results in low amounts of heat flow. Scientists Solomatov and Moresi introduced the term "stagnant lid" to describe the tectonic style of Venus in 1996. They noted that Venus has heat plumes rising to the surface and colder parts of the lid sinking back down. Mars is also believed to have stagnant lid tectonics, though its activity is much slower than Venus.
This article is a child-friendly adaptation of the Wikipedia article on Lid tectonics, available under CC BY-SA 4.0.