Ocean Floor's Three Major Regions: Continental Crust Is Not One

Continental crust is not a region of the ocean floor. It's the thick, buoyant crustal layer underlying continents (30–50 km thick, granitic composition).

The Three Actual Ocean Floor Provinces

1. Continental Shelf
   • Submerged continental margin; legally part of continent (UNCLOS Art. 76)
   • Depth: 0–200 m (avg 130 m)
   • Width: km to 1,500 km (Siberian shelf)
   • Sediment: thick, terrigenous; resources (oil, gas, sand, fisheries)
2. Continental Slope
   • Steep descent (2–10°) from shelf break to deep ocean
   • Depth: 200–3,000+ m
   • Features: submarine canyons (turbidity currents), slumps, cold seeps
   • Transition: crust thins from continental to oceanic
3. Deep Ocean Basins (Abyssal Plains + Rise)
   • Abyssal plains: 3,000–6,000 m; flattest places on Earth (fine pelagic sediment)
   • Abyssal hills: 100–1,000 m relief; original seafloor fabric
   • Mid-ocean ridges: divergent boundaries; volcanism, hydrothermal vents
   • Trenches: convergent boundaries; deepest points (Mariana 10,984 m)
   • Seamounts/guyots: volcanic, often flat-topped

Crustal Distinction

Why It Matters

The continent–ocean boundary (COB) at the slope base defines: legal continental shelf (resource rights), plate tectonics (ridge push, slab pull), and sediment routing (source to sink).

Continental crust underlies the shelf—but the shelf is the ocean floor province.