Shorelines are the areas between low tide and the highest level on land affected by storm waves. Approximately 67% of the world's population is concentrated in narrow bands adjacent to shorelines. In addition, coastlines often provide a convenient storage place for sediment derived from a continental mass. The Atchafalaya Delta, LA, is a good example of a river dominated (bird's foot) deltaic complex (Landsat image). Read about Louisiana's Barrier Islands:
A Vanishing Resource ... in the link given in the Chapter Heading.
The wave length is the distance from peak to peak or trough to trough and the period is the time it takes for two crests to pass a given point.
Wave base is one half of the wave length. When the depth of the water is less than the wave base the wave begins to interact with the floor of the ocean or lake. The wave length decreases and the velocity increases. Water molecules are displaced towards the shore and breakers form.
Shorelines tend to be irregular in shape and the waves generally approach the shore at some angle other than 90 degrees. Part of the wave may be influenced by wave base and begin to break, whereas the rest of the wave may not be modified. The net effect is for the waves to bend (refraction) so that the wave hits the beach nearly parallel to the shoreline. Even a slight angle of approach can cause water between the breakers and the beach to flow parallel to the coastline, producing a longshore current. These currents are extremely influential on the sand budget of the beach as they transport large quantities of sediment along the coastline. Rip currents are created when water piled up on the beach and transported laterally flows back through the breaker zone.
The average composition of the total dissolved solids in sea water is:
5 X 1013km
5 X 1018cm2
5 X 1018 cm
1.1 x 1024 cm3
1.1 x 1024 cm
1.1 x 1018 cm 3
1.15 x 1024 cm
1.15 x 1024 grams
11.5 x 1024 grams
.12x 1016 tons
1.2 x 1016 tons
12. x 1016 tons
Sodium present in the oceans is equilivant to what would be produced by the chemical weathering of about 1 km of continental rock.
|Textbook Home Page
|Glossary of Geologic Terms||Search These Pages|Other Courses|Resources|Grade Book|
Copyright by John C. Butler, July 29, 1995