This week my family and I chose to visit Trinidad, California. One of the reasons that I wanted to visit Trinidad, California is because of my interest in coastal erosion and the causes and effects of it. The Trinidad area is underlain by a geological unit referred to commonly as the Franciscan Formation. Franciscan rocks have their origins in the deep sea, where they were formed by currents that deposited sand, mud, gravel, and silica from the shells of marine creatures. These substances hardened to form sandstone, shale, conglomerate, greenstone, and chert over millions of years.
What most interested me in the area of Trinidad, California was the fact that not only is it in the center of a major seismic activity zone, but also the fact that it is subjected to the forces of coastal erosion.
Here is a picture which depicts the zone designated for the Trinidad Fault:
(Martin, 2007)
Additionally, here are a couple of pictures that depict the
loss of the cliffs of Trinidad due to coastal erosion:
Fig. 5 Active sea cliff erosion at Tsurai Village (source:
City of Trinidad GIS) (Martin, 2007)
The questions that my trip to Trinidad, California prompted me to ask are:
1) What is the rate of coastal erosion in and near the city of Trinidad, California?
a. I am asking this question because I believe that it is essential to understanding the constantly changing coastline of Trinidad, Ca, in order to estimate both past and future deformation of the coastline due to coastal erosion, primarily caused by waves, uplifting of the coastline, and a rise in sea level. Has this area been eroding since its formation, or is it only in recent times that erosion has become a major concern?
2) How many tectonic plates are in play when considering the geology of Trinidad, Ca?
a. It is known that most, if not all, of the coast of Northern California and Southern Oregon is subjected to high seismic activity due to the fact that multiple tectonic plates collide in this area to form the Cascadia Subduction Zone. Is this a safe area to live in? Has it reached its most final form or are more changes slated for the future?
3) What story do the fossils found in the greater Trinidad area tell us about the geological history of the Trinidad, CA area?
a. It is known that most, if not all, of the Trinidad area was formed due to the subduction of an oceanic plate beneath western North America. We have found, and would expect to find marine based fossils, but are there other fossils present that do not back up the hypothesis concerning the formation of this area? As we know, fossils can often provide a corroborating record to a hypothesis concerning the geology of a certain area. I am interested in finding out whether or not what we are finding here is consistent with expectations.
Trinidad, California is a beautiful place to visit, but I definitely would not plan to live there long term. Due to the coastal erosion challenges and continued seismic activity of this zone, I would not feel save putting down roots in this area, and would live in hear that my property would become damaged and that my family may not be safe.
Martin, K. (2007). Background Report: Geologic and Seismic Characteristics of Trinidad, CA [Ebook] (p. 4). Steamline Planning Consultants. Retrieved from http://trinidad.ca.gov/sites/trinidad.ca.gov/files/library/PlanningCommission/GeneralPlanUpdate/Background/trinidad%20geology.pdf
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