the.com/rift valley

means A long, low valley formed where tectonic plates are pulling apart and the land between them drops down as the crust stretches and cracks.

from 'Rift' comes from Old Norse 'ripta' or related Scandinavian roots meaning to break or tear apart, entering English around the 14th century for a split or cleft. Geologists later borrowed the word for exactly this kind of tearing on a planetary scale — most famously the Great Rift Valley system in East Africa, where the African continent is slowly splitting into two plates, a process so gradual it's measured in millimeters per year yet will, given enough millennia, open a new ocean.