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.
The East African Rift, the Baikal Rift Valley, the West Antarctic Rift, and the Rio Grande Rift are Earthâs major active continental rift valleys. The East African Rift is part of the âGreat Rift Valleyâ system discussed below.