1. Chapter 16 The Marine Environment

2. Longshore currents Waves usually approach the beach at an angle Water recedes parallel to the beach. Waves usually approach the beach at an angle Water recedes parallel to the beach.

3. Longshore currents This repetitive wave motion creates a flow of water in one direction along the shore. The waves do deflect depending on the shape of the coast. The larger the waves the strong the current. Waves produce erosional and depositional landforms on beaches. This repetitive wave motion creates a flow of water in one direction along the shore. The waves do deflect depending on the shape of the coast. The larger the waves the strong the current. Waves produce erosional and depositional landforms on beaches.

4. Groins will catch sand carried by the Longshore current. Which way is the Longshore current flowing in this picture?

5. Jetties and Seawalls

6. Erosional landforms Water crashing on the beach as surf will erode material away - even solid rock. Headlands receive most of the wave force because of wave refraction. Water crashing on the beach as surf will erode material away - even solid rock. Headlands receive most of the wave force because of wave refraction.

7. Erosional landforms Sea stacks Wave cut platform Wave cut cliff Sea caves Sea stacks Wave cut platform Wave cut cliff Sea caves

8. Beaches Beaches can be mud, sand, pebbles, cobbles, gravel, or rocky. Color of the sand depends on material eroded. Beaches can be mud, sand, pebbles, cobbles, gravel, or rocky. Color of the sand depends on material eroded.

9. Beaches Hawaii has black sand beaches in some locations. The eroded material is dark volcanic rock. Hawaii has black sand beaches in some locations. The eroded material is dark volcanic rock.

10. Beaches Florida and the Bahamas white and pink sand beaches are bits of local coral and sea shells.

11. Estuaries Occur where a river meets the sea. Formed by rising sea level flooding a river valley. Water is brackish These areas provide an excellent environment for wildlife. (protection, quiet water, food) Occur where a river meets the sea. Formed by rising sea level flooding a river valley. Water is brackish These areas provide an excellent environment for wildlife. (protection, quiet water, food)

12. Depositional landforms Spit Which way is the current flowing? Spit Which way is the current flowing?

13. Depositional landforms Tombolo

14. Depositional landforms Baymouth bar

15. Depositional landforms Lagoon Bay Lagoon Bay

16. Depositional landforms Barrier Island

17. *** Coastal landforms Depositional Beach Spit, Baymouth bar Tombolo Bay or Lagoon Barrier Island Longshore bar Sand bar Depositional Beach Spit, Baymouth bar Tombolo Bay or Lagoon Barrier Island Longshore bar Sand bar Erosional Beach Sea stack Wave cut platform Wave cut cliff Sea cave Estuary Erosional Beach Sea stack Wave cut platform Wave cut cliff Sea cave Estuary

18. Oceanic and Continental Crust Continental margins (Figure 16-12) –Continental shelf (avg. width 60 km) –Continental slope (10% drop off, edge of continent) –Submarine canyons (cut by turbidity currents) –Continental rise (gentle slope of sediment) –Trenches ( no continental rise can be 11 km deep) Continental crust is 40 km thick on average Oceanic crust is 7 km thick on average Continental margins (Figure 16-12) –Continental shelf (avg. width 60 km) –Continental slope (10% drop off, edge of continent) –Submarine canyons (cut by turbidity currents) –Continental rise (gentle slope of sediment) –Trenches ( no continental rise can be 11 km deep) Continental crust is 40 km thick on average Oceanic crust is 7 km thick on average

19. Ocean Basins Abyssal plains - large flat areas covered by (hundreds of meters thick) sediments Deep sea trenches (most on the edges of the Pacific Ocean). Trenches are 100 km wide and extend thousands of km. Abyssal plains - large flat areas covered by (hundreds of meters thick) sediments Deep sea trenches (most on the edges of the Pacific Ocean). Trenches are 100 km wide and extend thousands of km.

20. Ocean floor bumps Mid-ocean ridges –1500 m tall –Thousands of km wide –Many thousands of km long Rifts extend along the ocean ridges in many places Volcanic activity and earthquakes are common at the mid-ocean ridges Mid-ocean ridges –1500 m tall –Thousands of km wide –Many thousands of km long Rifts extend along the ocean ridges in many places Volcanic activity and earthquakes are common at the mid-ocean ridges

21. More interesting bumpy stuff Isolated seafloor volcanoes There are tens of thousands of these mountains dotted across the ocean floor Some break the surface of the water as volcanic islands (Azores, Iceland, etc.) Others are extinct volcanoes –Seamounts - submerged volcanoes –Guyots - flat top mountains Isolated seafloor volcanoes There are tens of thousands of these mountains dotted across the ocean floor Some break the surface of the water as volcanic islands (Azores, Iceland, etc.) Others are extinct volcanoes –Seamounts - submerged volcanoes –Guyots - flat top mountains

22. Marine sediments Reference maps: Physiographic Map of Earth on pages 912-3 in text. NOAA Marine Sediment Thickness Map Reference maps: Physiographic Map of Earth on pages 912-3 in text. NOAA Marine Sediment Thickness Map

24. Ocean Floor Examine and interpret bathymetric, topographic, and relief data.

25. Tsunami Dec 26, 2004 Caused by earthquake of magnitude 9.0 Fourth strongest quake since 1900 Off the coast of Sumatra, Indonesia Dec 26, 2004 Caused by earthquake of magnitude 9.0 Fourth strongest quake since 1900 Off the coast of Sumatra, Indonesia

26. Tsunami animation