1. Continental Margins: Active vs. Passive

2. Different Continental Margins

3. Active vs. Passive There are two types of margins:
Active (Pacific-type)
Passive (Atlantic-type)
Both are influenced by the process of plate tectonics such as:
Erosion, deposition, uplift and subsidence
Also influenced by climatic changes such as sea level rise and fall due to changing ice caps.

4. Active Continental Margin

5. Passive Continental Margin

6. Active Margins Located near or adjacent to a plate boundary.
Earthquakes & volcanic activity.
Most commonly a subduction zone.
Dominated by erosional features as shoreline is retreating landward.
Narrow continental shelf, steep continental slope, and continental rise is commonly absent.
Sediment poor; falls in trenches

7. Active Margins

8. Active Margins – Erosional Features
Erosional coasts with cliffs and narrow beaches.
Big Sur, Central California

9. Active Margins – Erosional Features
Sea Stacks & Sea Arches
Cabo San Lucas
Pocket Beaches
Features show where land “used” to be. Terraces show ancient shorelines.
Marine Terraces of San Clemente Island

10. Active Margins – Landslides

11. Passive Margins Located far from active plate boundaries.
Continental margins usually surround an active spreading center.
Dominated by depositional features as shoreline is building outward.
Wide continental shelf, moderate continental slope, and a well developed continental rise.
Sediment-rich

12. Passive Margins

13. Passive Margin – Depositional Features
Chesapeake Bay shows drowned valleys, capes, and barrier islands.
Sediment from the continent is building outward, not eroding.
Cape

14. Passive Margin – Depositional Features
Barrier Islands
Capes (Cape Cod)
River Deltas
Barrier Island – Manhattan Island

15. Passive Margin – Beaches
Wide beaches that are very flat. No cliffs. Lots of sediment!!!

16. Passive Margin – Hazards
Barrier Island before hurricane Ivan and after hurricane Ivan. A lighthouse is shown in the box.

17. Passive Margin – Hazards
Climate change is causing the ice caps to melt. If they completely melt, this is what will happen to passive continental margins.