resistance of inland materials, which can be transported to the coast by 

 terrestrial processes, also contribute to the geomorphic variability of coasts. 



Climate 



Climate and weather are terms used to describe a broad group of interre- 

 lated atmospheric processes. Weather characterizes the overall state of the 

 atmosphere on short time scales of minutes to months. Climate, in contrast, 

 characterizes the long-term conditions of an area, using averages together with 

 measures of dispersion and frequency. 



Several interrelated climatic factors such as temperature, pressure, wind, 

 and moisture have a great influence on the development of the coastal zone. 

 These factors may change as long-term trends, and also display cyclic and 

 noncyclic variations. Distinctive cyclic variations include seasonal and daily 

 changes associated with the revolution and rotation of the earth. Regional 

 variations in paleoclimatic and modern climatic factors also contribute to the 

 spatial variability of coastal geomorphic features. Of the various climatic 

 factors, wind most strongly influences modern process and geomorphic vari- 

 ability of coasts, both directly and indirectly. Wind is discussed subsequently 

 in a separate section. 



Evidence from stratigraphic, paleontologic, palynologic, radiometric, 

 pedologic, and archeologic data shows that many climatic changes of global 

 and regional scale have occurred throughout geologic time. While the long- 

 term paleoclimatic history of the earth is not well known, paleoclimatic data 

 assist in characterizing general aspects of the many profound and widespread 

 changes that have occurred throughout geologic time. 



Most evidence indicates that over the last 500 million years, the earth was 

 warmer than present, with the poles being ice-free most of this time (Frakes 

 1979; Lamb 1982). About 55 million years ago, global climate began a long 

 cooling trend, which led to the development of the high-latitude ice sheets. 



Superimposed upon this trend, over the last 1 to 2 million years during the 

 Quaternary period (Pleistocene and Holocene epochs), are a number of alter- 

 nating glacial and interglacial episodes. In the Northern Hemisphere, these 

 episodes were characterized by widespread waxing and waning of the ice 

 sheets into the mid-latitudes. Falling and rising temperatures in both hemi- 

 spheres accompanied glacial advance and retreat. During cooler periods, 

 more widespread glaciation of high altitudes was also common. 



These climatic changes were accompanied by large fluctuations in sea 

 level. During glaciations, water was withdrawn from the ocean basins and 

 stored in ice sheets and mountain glaciers. During interglacial periods, it 

 returned to the ocean basins. Many of the large inland lakes also may have 



Chapter 2 Relevant Processes and Factors 



