The answer is;
The rift valley formed when the crust pulled apart.
The rift valley formed at a divergent boundary.
Divergent boundaries occur when two adjacent convection currents in the mantle are spinning in opposite directions. This causes the upper crust to stretch creating tension due to drag in different directions on the local region. The tension causes the crust to crack severally and the middle crust block dropping in comparison to flanking regions.
I would believe the answer is 1. but science is not my strong suit
The answer is cell organelles.
