A cohort is a group of people who share a common characteristic or experience within a defined period (e.g., are currently living, are exposed to a drug or vaccine or pollutant, or undergo a certain medical procedure).
A rift valley is a lowland region formed by the interaction of Earth's tectonic plates. This small rift valley has a typical formationâlong, narrow, and deep. It was formed by the Thingvellir rift, where the North American and Eurasian tectonic plates are tearing, or rifting, apart over a hotspot on the island of Iceland.
When this landmass started to split, gashes in Earth's crust called rifts opened up along pre-existing weaknesses. One of these gashes, called the West Africa Rift System, started to tear apart the future Sahara desert. Two more rifts formed along the future boundaries of South America and Africa.Imagine three rift zones, two lined up essentially north-south and one pointing east-west. These alignments are key to explaining why the continents broke apart the way they did, according to a study published March 6 in the journal Geology.he mantle is the hotter layer of rock beneath Earth's crust. The crust often breaks apart at three-pronged junctions, such as the triple rift that formed between Africa-South America, and it's not uncommon for one rift to fail to develop.