Geology 101 Name Reading Guide for Ch. 19: Shores and Coastal Processes (p. 612) Waves, Currents, and Tides (p. 614) Waves and Currents (p. 614) Imagine that you can see a side view of a wave as it approaches a beach. Describe how the wave changes as the wave approaches the beach. From a map or plan view, waves bend as they approach the beach. This bending is termed. This is created because the waves slow in shallower water. Since the water depth increases gradually offshore, as an individual wave approaches the shore, one part of the wave will travel faster than another part of the wave. Even though waves bend as they approach the beach, they wash up on the beach at an angle. This creates a current which forms a movement of sand along the beach. Waves in the ocean are surface waves. That is, they affect the surface and a short distance below the surface (down to a distance of about one-half the wavelength of the waves). Water below this level is not affected by the wave action above. (Water waves do not affect submarines when they are in deeper water.) In a later section you will read about the movement of sediment along a coast. For this sediment to move by wave action, the water must be relatively shallow-- less that one-half the wavelength of the waves. Sediment is not transported in deep water by wave action. Tides (p. 616) Please read this section, but you will not be tested directly over this information.
Processes that Shape Coasts (p. 620) Coastal Erosion (p. 620) Use the illustrations in this section to sketch a series of drawings that show how a sea stack forms. Please label your sketches. Show the wave refraction that occurs as waves approach the coast. I will not evaluate the quality of your sketches! Notice the sea stack on the photo of a part of the Washington coast. Why do the wave crests behind the sea stack appear different? In what way does this change in wave direction responsible for the sea stack? (Hint see the illustration of the formation of a sea stack on page 623)? Draw on the photo what the coast would have looked like before the formation of the sea stack. Wave crests Forested coastline Sea stack
Coastal Transport and Deposition (p. 624) In the diagram below: 1) determine the direction of the longshore transport along the coast 2) sketch on the diagram how the coast will change over time 3) label the diagram (An aside--you do not have to answer this question--where in Washington do we see similar landforms?)
The Santa Barbara shore has been the site of an on-going problem with longshore drift and a harbor for small boats. Illustrate on the diagram below how the area changes with the addition of the breakwater. In attempt to add to beaches that are shrinking, people have installed rock walls perpendicular to the shore. These are termed. Assume that these have just been installed along a coast in the diagram below. Illustrate the changes that would occur as a result of their installation. What effects would this have farther down the coast?
Types of Coasts (p. 631) The only parts of this section you need to read carefully are the subsections entitled The East Coast of North America and the subsection The West Coast of North America. The other parts of this section are interesting-- barrier islands and organic coasts-- but they are not very applicable to the Pacific Northwest. Plate Tectonic Settings of Coasts (p. 637) The east coast of the US is along a quiet (passive) plate margin, while most of the west coast is more active tectonically. In what ways are the coasts different? Sea-Level Fluctuations and Coastal Erosion (p. 639) During the last glaciation, the ocean level was about 425 feet than the present sea level. Why did this sea-level change occur? Sea level may also change due to: 1) 2) 3) 4) Remember sea level is the line created by the level of the water and the level of the land, so both contribute to global sea level.