Which sequence correctly describes the stages when continents begin to break apart?

Which sequence correctly describes the stages when continents begin to break apart?

• A. Initial uplift → rift valley formed → new ocean basin formed → ocean widens
• B. Oceans widen → initial uplift → rift valley → new ocean basin
• C. Rift valley formed → ocean widens → initial uplift → new ocean basin
• D. New ocean basin formed → rift valley → initial uplift → ocean widens

Answer: (A)

Continental breakup proceeds through a sequence driven by stretching of the lithosphere. First, the extended crust uplifts as tensional forces thicken and buoyant materials respond to thinning. This initial uplift sets up the conditions for fracturing. Next, the stretched crust breaks and subsides along faults, forming a rift valley as the crust splits into blocks. As rifting continues and the valley deepens, water can flood in, creating a new ocean basin where sea-floor spreading will later generate new crust. Finally, the ocean basin widens as new oceanic crust forms at mid-ocean ridges and the two sides move apart, expanding the ocean. That matches the progression: initial uplift → rift valley formed → new ocean basin formed → ocean widens. If the steps were reordered, you’d have water invading before the rift existed or uplift occurring after rifting, which doesn’t align with how continental breakup naturally unfolds.

Continental breakup proceeds through a sequence driven by stretching of the lithosphere. First, the extended crust uplifts as tensional forces thicken and buoyant materials respond to thinning. This initial uplift sets up the conditions for fracturing. Next, the stretched crust breaks and subsides along faults, forming a rift valley as the crust splits into blocks. As rifting continues and the valley deepens, water can flood in, creating a new ocean basin where sea-floor spreading will later generate new crust. Finally, the ocean basin widens as new oceanic crust forms at mid-ocean ridges and the two sides move apart, expanding the ocean. That matches the progression: initial uplift → rift valley formed → new ocean basin formed → ocean widens. If the steps were reordered, you’d have water invading before the rift existed or uplift occurring after rifting, which doesn’t align with how continental breakup naturally unfolds.