INTRODUCTORY
OCEANOGRAPHYINTRODUCTORY
OCEANOGRAPHY
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I know very few of us who would not love to live for a time at the coast, and swim in the ocean or walk on the beach, or be lulled to sleep listening to the surf through the open window of a seaside cottage. Those of us who have spent time doing just that have discovered coastal regions of our continents with widely varying landforms, topography, and histories. This lesson classifies and discusses those coastal regions and the effect that man-made barriers have on the natural processes of the beach. In North Carolina, we are fortunate to live on one of the most beautiful coasts in the world, and one of the most interesting geographically and dynamically (as shown on the left in Fig. 12.2).
Coastal waters differ from oceanic waters mainly because of their close proximity to land. These are the waters most affected by human activity. Runoff from land (and whatever pollution it contains) spreads out over its surface. Ships, spaced so widely in the open ocean, converge to coastal ports, making these water congested and often polluted by the pumping of bilges, or worse still, by the spilling of millions of gallons of crude oil or toxic material when ships collide or run aground. These are the waters that are dredged, and into which garbage and dredge spoils and sewage is dumped. These are the waters in which our largest concentrations of fish are found, a fact not always in harmony with what we do to these waters.
Coastal waters also include estuaries, semi-enclosed bodies of water in which seawater mixes with freshwater, and adjacent to which are our extremely important marine wetlands.
There usually is no clear demarcation line between coastal waters and the ocean to which they belong -- usually it includes those waters on the shelf closest to land. There are, however, bodies of water set-off by sills or island arcs from their parent ocean that are called marginal seas. We also will discuss some of these marginal seas and how they were "isolated" from their parent ocean.
At the end of this lesson, you should: (1) Be able to describe the difference between coastlines and shorelines; (2) Explain why and how the coastal region is classified into different offshore regimes; (3) Explain how wave action moves sediment in the dynamic zone along a shoreline by longshore drift; (4) Describe how the equilibrium of a beach and its slope are determined by grain size; (5) Describe th usually disastrous effect of constructed barriers on the beach; (6) Explain the primary difference between coastal and oceanic waters; (7) Explain how density gradients set up by the flow of fresh water into the ocean may create coastal geostrophic currents; (8) Define and explain the importance of estuaries and their attached marine wetlands; (9) Define marginal seas and explain how they are formed; (10) Describe the unique circulation patterns or salinity structures of some representative marginal seas.
Garrison, OCEANOGRAPHY, An Invitation to Marine Science, 4th Ed. Chapter 12, pages 288-318.
To keep the timing of your learning consistent with the class schedule, this lesson has been divided into two parts. You may link to each below:
Part 1 contains a discussion of the classification of coastlines, including erosional and depositional coastlines.
Part 2 contains a discussion of the effect of artificial structures in the dynamic zone, and the beach equilibrium slope. CONTAINS AUDIO COMPONENTS
Part 3 contains a discussion of coastal geostrophic currents, estuaries, wetlands and marginal seas.
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