Tectonics

Tectonics are the large scale geological processes that alter the structure of the Earth's crust.

The rigid outermost shell of the planet is called the lithosphere and consists of the crust and upper mantle. The lithosphere is fractured into a number of plates that slide across the lower mantle forming cratons and oceanic trenches.

The lithosphere is believed to have formed approximately 4 billion years ago with the cooling that followed the initial Hadean eon of Earth. This cooling allowed a crust to form on the Earth’s surface and from the early formation of the lithosphere onwards continents have been building up, breaking apart and moving around the globe.

The fissures at the base of oceanic trenches are caused by plate tectonics and these are now being looked to as a possible source for the origins of life. Many astrobiologists suspect that tectonic plate activity in other planetary bodies may be a sign of potential life.

It’s hypothetical that tectonic plate activity not only 'produces' life but also forms the primary engine that 'drives' the evolutionary processes that follow. Variation in the gene underpins biological evolution. In a similar fashion variation in the environment underpins extinction and repopulation rates. The primary force for environmental change during the life of a planet is tectonic plate activity, as it forms and breaks apart continents, creates and empties oceans, pushes up mountains and causes extreme temperature variation.

Tectonic plate activity may not be the sole driver of environmental processes - particularly once life has emerged and biological feed-back loops start to occur - however it may be the single largest factor that affects the formation and evolution of life on a planet.