The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another; divergent ... troughs such as the Great Rift Valley in Africa form where ...

As the rift opens, ocean water may invade. The shallow waters of the rift valley can be ideal environments for limestones to form. Here is a nice summary of sedimentation on divergent margins ... they ...

Running along the top of this chain of mountains is a deep crack, called a rift valley. It is here that ... At the East Pacific rise, which is pushing a plate into the west coast of South America ...