The Wilson cycle. Plate tectonics over time
The tectonic plates, and the distribution of continents and oceans has changed over time. Tuzo Wilson proposed an explanation that explains, in an orderly way, the process of opening and closing an ocean, summarizing what happens at the constructive and destructive edges of tectonic plates.
The phases of the Wilson cycle are:
- Rift stage. In a stable craton, a hot spot causes the lithosphere to heat, stretch, and thin until it breaks. The continent is divided and a new divergent plate edge is created. For example, the African Rift Valley.
- Red Sea stage. The continent has been divided, the two blocks are separated and a new oceanic lithosphere is generated. The oceanic ridge is a constructive edge. The continents are separated by a small ocean basin, like the Red Sea.
- Atlantic ocean stage. The continents continue to separate and the ocean basin grows wider and wider, with a well-developed ridge, as in the Atlantic Ocean.
- Pacific ocean stage. When the oceanic basin has already grown enough and is old, the edges that are in contact with the continents cool down and become more dense, forming a subduction zone in which a new convergent edge is generated in which the lithosphere is destroyed. oceanic. Example, the Pacific Ocean , where arches of islands are created.
- Andean orogen stage. A subduction zone develops under the edge of a continent, disappearing the ocean. The sediments of the oceanic lithosphere fold and form a mountain chain that borders the continent, as in the case of the Andes mountain range .
- Himalayan orogen stage. When most of the oceanic lithosphere has subducted and the two continents are about to collide, obduction occurs, until a single continent is generated and an intercontinental mountain range is formed. Such a collision orogen occurs, for example, in the Himalayas.