What happens during continental rifting?

• A. Rift zones may fill with water and become new oceans
• B. Continental crust thickens and uplifts to form mountains
• C. Oceanic trenches form as continents collide
• D. Crust becomes completely brittle and remains static

Answer: (A)

Continental rifting is an extensional process where a continent is pulled apart. As the crust stretches, it thins and breaks, forming rift valleys and faults. If rifting continues, new oceanic crust can begin to form as magma upwells and the landmass splits apart. Eventually seawater can flood into the widening gap, creating a new ocean basin between the separating continents. That’s why rift zones may fill with water and become new oceans.

Why the other ideas don’t fit: thickening and uplifting of crust happen during mountain-building from compression, not extension. Oceanic trenches arise where one plate sinks beneath another at subduction zones, not from rifting. Crust doesn’t stay completely brittle and static during rifting; the process is dynamic, with ongoing extension, faulting, and magmatic activity that thins and reshapes the crust.