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.
First named by the British explorer John Walter Gregory, the Great Rift Valley is an enormous geological feature that runs for 5,000km from northern Syria in southwestern Asia â¦ to central Mozambique in East Africa.   Africa's Great Rift Valley is a 6,000 km (3700 mi) crack (fissure) in the earth's crust, stretching from Lebanon to Mozambique.