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.
What is the Great Rift Valley?     Africa's Great Rift Valley is a 6,000 km (3700 mi) crack (fissure) in the earth's crust, stretching from Lebanon to Mozambique. Where is the great rift valley located? The Great Rift Valley is in Eastern Africa, extending from the  south side of the Red Sea to Mozambique.