ANAHEIM SLOUGH


at
Seal Beach National Wildlife Refuge:
Long Beach 1933 Earthquake Affects Anaheim Estuary's Tidal Mudflat Wetland
Observations and Quoted Excerpt from
George MacGinitie and Nettie MacGinitie
California Institute of Technology
Kerckhoff Marine Laboratory
Corona Del Mar at Newport Beach
and
Edited by
Robert 'Roy' J. van de Hoek
Field Biologist & Geographer
Sierra Club and Wetlands Action Network

**In the severe southern California earthquake of March, 1933, we observed a phenomenon which was interesting to both zoologists and paleontologists. Mud flats at Anaheim Slough, near Long Beach, were thrown into mounds. These mounds were about 8 feet in diameter and from 18 inches to 2 feet high. As a result, some of the burrowers were raised higher than usual with respect to tide. The consequences in this instance were not vital, because the mounds were smoothed out by tidal action within a month.

Suppose, however, that at the same time the entire land surface had bee raised with reference to tide level. Then the mounds would have remained permanently fixed, and the upper layers of sand would ever after have remained irregularly placed in conformity with topography of the mounds. Such permanently fixed mounds are abundant in the San Joaquin Valley of California, where they are known as hog wallows. In these the configuration of the surface strata follows the contours of the mounds, just as would have been the case at Anaheim Slough had the land surface been raised. **

**Quoted Excerpt Source = Natural History of Marine Animals. By George MacGinitie and Nettie MacGinitie, 1949, on page 96.** For further information on the MacGinities as marine biologists, see the web pages under Marine Biology and MacGinitie Anthology.



Closing Comment
by
Robert 'Roy' J. van de Hoek
Field Biologist and Geographer

The reference of Anaheim Slough in association with the Long Beach 1933 Earthquake, was especially interesting to me for several reasons. First, it showed the serendipity and good fortune of the MacGinities as "naturalists" to be in the "field" to observe the phenomenon. Second, George MacGinitie lived and went to school at Fresno, so he put his knowledge of history from the Fresno "plain" or "inland sea" of "hog wallows" and associated them with the Anaheim coastal wetlands-estuary at Anaheim Slough. Third, MacGinitie's tidal mudflat mounds seem that they could form in other estuaries as well, such as the Ballona Wetlands when an earthquake occurs there. A new earthquake fault has been discovered at the Ballona wetlands. And lastly, the anecdotal observation is good ecological and historical information, now that it is nearly 70 years since the Long Beach Earthquake occurred. It is fascinating that marine biologists such as George MacGinitie would have made a natural history observation about earthquake's impact on an estuary and related it to the "California Prairie" at Fresno.

Today, in 2001, 68 years after 1933, Anaheim Slough is part of the Seal Beach National Wildlife Refuge, but under U.S. Navy ownership as a Weapons Center. And a part of Anaheim Slough has been lost to dredging for a yacht harbor called Huntington Marina. Did the impact of the earthquake affect the portion of Anaheim Slough where today the Marina is located or within Seal Beach National Wildlife Refuge or in both areas?

Today, in 2001, 68 years after 1933, the San Gabriel River no longer enters directly into Anaheim Bay. However, in geological time, before humans, and in future time after humans are gone (or human population is decreased by plague, famine, and starvation due to overpopulation, water shortages and agricultural collapse from climatic change, the San Gabriel River will once again enter into the Anaheim Bay. Tidal creeks, or sloughs in the Anaheim Bay, will expand, and the Light-footed Clapper Rail and Belding's Savannah Sparrow will "reclaim" the marshes in their former abundance. 1