1. Maritime Environment Chapter 16

2. Erode Landforms: high energy and suspended rock fragments faster in deep water than in shallow water. Wave refraction : straight wave crests bend when part of the crest moves into shallow water due to the difference in wave speed.  Closer to shore: increase in height; called breakers Shoreline Features WAVES

3. Over time irregular shorelines are straightened by wave action. How did the engineers combat this in Dubai’s Palm Island? Erosional Landforms  wave crests bend towards the headlands Shoreline Features

4. Erosional Landforms Landforms of Rocky Headlands Shoreline Features –wave-cut platform –wave-cut cliff –Differential erosion –sea stacks sea arches and sea caves.

5. loose sediments size of sediment particles depends on the energy of the waves and on the source of the sediment. Beaches  sloping band of sand, pebbles, gravel, or mud at the edge of the sea. Shoreline Features

6. brackish–a mixture of freshwater and salt water. nurseries to the young of many different species. Estuaries  lower end of a freshwater river or stream enters the ocean. Shoreline Features

7. longshore current : current flowing parallel to the shore produced as water from incoming breakers spills over the longshore bar. Longshore Currents Shoreline Features

8. Longshore Currents Rip Currents Shoreline Features –flow out to sea through gaps in the longshore bar. –dangerous currents can reach speeds of several kilometers per hour. –you should not try to swim against it –swim parallel to the shore to get out of it.

9. –Spit: narrow bank of sand that projects into the water from a bend in the coastline. –baymouth bar forms when a growing spit crosses a bay. Barrier islands : –Sediment deposited or shaped by the longshore current –separated from the mainland. Depositional Features of Seashores  Built by longshore currents Shoreline Features

10. –Tombolo: ridge of sand that forms between and connects the island to the mainland. Depositional Features of Seashores – Lagoons: shallow, protected bodies of water behind baymouth bars and barrier islands Shoreline Features

11. Tides, currents, storm waves, and winds all play a role in building coastal features that rise well above sea level. Was this a concern for building Palm Island? Depositional Features of Seashores  *****All depositional coastal landforms, including large barrier islands, are unstable and temporary.***** Shoreline Features

12. result of global warming? seawater will warm and expand melting glaciers global sea levels could rise another 30 cm in the next 70 years. How would this affect us? Changes in Sea Level  100 years: global sea level has risen  10 to 15 cm and estimates Shoreline Features

13. Changes in Sea Level Effects of Tectonic Forces Shoreline Features –United States West Coast is being pushed up much more quickly than the sea level is rising. –emergent coast: formerly under water –relatively straight –exposed seafloor topography is much smoother than typical land surfaces.

14. Oceanic and Continental Crust  Earth has two types of crust:  thick continental crust  thin oceanic crust. The Seafloor Continental margins: submerged parts of continents continental shelf continental slope continental rise.

15. Continental Shelves The Seafloor continental shelf : shallowest part of a continental margin average depth is about 130 m most of the world’s continental shelves were above sea level during the last ice age.  home to large numbers of commercially valuable fishes. Thick sedimentary deposits on the shelves are also significant sources of oil and natural gas.

16. Continental Slopes  seafloor drops away quickly to depths of several kilometers The Seafloor Frequently marked by deep canyons that were cut by turbidity currents. Turbidity currents: rapidly flowing water currents along the bottom of the sea carry heavy loads of sediments, similar to mudflows on land.

17. Continental Slopes The Seafloor continental rise : gently sloping accumulation of deposits from turbidity currents forms at the base of the continental slope. Some times continental slope ends in deep-sea trenches no continental rise especially around the Pacific Ocean

18. Ocean Basins  deeper parts of the seafloor above the thin, basaltic, oceanic crust The Seafloor represent about 60 percent of Earth’s surface contain some of Earth’s most interesting topography.

19. Ocean Basins Abyssal Plains The Seafloor –smooth parts of the ocean floor 5 or 6 km below sea level. –covered with hundreds of meters of fine-grained muddy sediments and sedimentary rocks –deposited on top of basaltic volcanic rocks.

20. Ocean Basins Deep-Sea Trenches The Seafloor –elongated, depressions in the seafloor several kilometers deeper than the plains. –Many lie next to chains of volcanic islands –most are located around the margins of the Pacific Ocean.

21. Ocean Basins Mid-Ocean Ridges The Seafloor –chains of underwater mountains. –average height of 1500 m –may be thousands of kilometers wide. –frequent volcanic eruptions –earthquake activity. –often have valleys up to 2 km deep, called rifts, running through their centers.

22. Ocean Basins Hydrothermal Vents The Seafloor –hole in the seafloor through which fluid heated by magma erupts. –Most are located along the bottom of the rifts in mid- ocean ridges. black smoker hydrothermal vent ejects superheated water contains metal oxides and sulfides that produce thick, black, smokelike plumes. white smoker ejects warm water.

23. Seafloor Volcanoes  Most of the mountains on the seafloor are probably extinct volcanoes. The Seafloor 2 types –Seamounts: submerged basaltic volcanoes more than 1 km high. –Guyots: large, extinct, basaltic volcanoes with flat, submerged tops. *************Unlike features on land, seafloor structures persist practically forever due to a lack of erosional mechanisms****************

24. Marine Sediments Ooze The Seafloor –Sediments containing a large percentage of particles derived from once-living organisms are called oozes. –Most are small and made of either calcium carbonate or silica. –accumulate at a rate of only a few millimeters per thousand years. calcareous ooze lapping onto basaltic outcrop and talus

25. Marine Sediments Manganese Nodules The Seafloor –consist of oxides of manganese, iron, copper, and other valuable metals that precipitated directly from seawater. –millimeters per million years. –Manganese nodules cover huge areas of the seafloor.