Coastal Erosion Field Trip

Solana Beach to Del Mar, San Diego County, California
by Chris Metzler
Professor, MiraCosta College
Oceanside, CA

This series of pages is a guide to coastal erosion in the northern part of San Diego County, California, from Fletcher Cove in Solana Beach to the mouth of the San Diego River in Del Mar. It is designed to serve several function. It can be used as a preview or review for those that attend a field trip in association with geology, oceanography or geography courses and wish to examine the area before or after their visit. Also, it can serve to aid those that, due to limitation in mobility, or other circumstances, cannot actually attend the field trip. Finally, it can provide a taste of the field experience for those that cannot visit the field trip site owing to their distance from the field trip location.

It is important to realize, though, that looking at photos and reading text on a screen cannot replace the actual experience of the field trip. The detail that can be examined in the field is not comparable to the resolution on a computer screen. In addition, visitors to the field site can enjoy the mild breezes off the Pacific Ocean, the occasional pods of dolphins which swim by, the feel of the warm sun, and other myriad experiences which are not available in the on-line mode of learning.

Introduction:


The northern San Diego County (California) shoreline is an emergent coast, meaning that, in the last several million years, the shoreline has been gradually rising. Consequently, the shoreline is relatively steep, compared to those on the southeast coast of the United States, or the Gulf of Mexico Coast, for example. As sea level has risen and fallen, due to repeated advance and retreat of glaciers during the Ice Ages, the shoreline has developed a series of uplifted marine terrace, or wave-cut terraces. (The most prominent of these terraces forms the major level area along the northern San Diego County shoreline, where the older parts of the cities of Oceanside, Carlsbad, Encinitas, Solana Beach, Del Mar and La Jolla are located.) Currently, the ocean ward edge of the marine terrace is being eroded by ocean waves as well as by ground water seepage and other processes. This forms a well-developed bluff or sea cliff along the shoreline.

On this field trip we will examine the natural as well as human-induced causes of this coastal erosion. We'll look at the variety of factors which control the erosion process and discuss possible approaches to deal with the problem.