constructive plate margin landforms

Question 1

how are rift valleys formed?

Answer 1

• triggered by plume of magma beneath crust - hot spot
• plates move apart from each other as a result of convection currents
• magma able to escape through weakened continental crust
• sections of the crust subside into the mantle to form basins (grabens)
• blocks of crust slide along parallel faults - multiple fracturing gives a stepped appearance to the side of a rift valley
• lakes are present on the valley floor
• central plateau left behind, raised block (horst)