December 30, 2011

Cabrillo National Monument in San Diego

Cabrillo National Monument sits out at the end of Point Loma, marking the northern entrance to San Diego Bay. This was the first place in what is now United States territory, that a European set foot on the Pacific Coast when Juan Rodriguez Cabrillo landed here in 1542. Woodrow Wilson set this area at the end of Point Loma aside in 1913 to commemorate his landing here. Today it serves as a rare island of preserved coastal sage scrub and rocky tidepools in a sea of urban development that is now San Diego.

Extreme low tide at Cabrillo National Monument

When we arrived, it was extreme low tide along the coast, exposing huge sections of boulders and tide pools. There were tons of people out there playing amongst the seaweed and pools. I spoke to a park ranger who was out on patrol. She explained to me that while they want people to experience and appreciate these tidepools, the sheer number of them is having an affect. They have seen the populations of a variety of coastal species decline dramatically in the last 20 years, abalone being the hardest hit. They have been discussing what can be done to mitigate the impacts of so many shoes and fingers on these creatures.

Hilina examining some creatures in a tidepool

However, the good news is that the tip of Point Loma, out by the lighthouse is closed to the public and thus those pools have not been affected. So, they do have some direct comparisons they can show between the two main areas. Unfortunately, for reasons not entirely explainable, abalones have all but disappeared from that area too. Some speculate it could be illegal poaching to sell on the Asian markets.

The lighthouse at the tip of Point Loma with exposed tidepools

The geology of Point Loma is equally fascinating. The rocks at the lower levels are near horizontal layers of rocks laid down in an underwater canyon some 70 million years ago. They are called turbidites and they represent silt and sand that flowed down and accumulated in the canyon crevices, almost like a slow-moving river of sediment. Within those layers are fossils of clams and other marine organisms. Above those horizontal layers are weakly cemented sandstones that are much more recent. These sandstones erode easily into deep gullies and steep cliffs. Without the fragile coastal sage scrub holding it together, it virtually melts into the sea.

Cliffs along the coast of Point Loma
The area that this sandstone exists in (across much of Southern California) has experienced a great deal of erosion over the decades, first by the grazing of animals like sheep and later by urban development. Only protecting these sage scrub ecosystems, which thrive in the dry, hot, salty environment of this region, keeps the entire hillside of melting away.

Turbidite layers along the tidepools
At the top of Point Loma is the visitor center with spectacular views out across San Diego Bay to downtown and off to the Laguna Mountains beyond, south into Mexico, and out across the Pacific Ocean.

A view out toward Tijuana (white area in distance) with Cabrillo status on right
There is also a whale watching platform facing the ocean, where we saw several gray whales spouting offshore. They are just beginning their slow migration northward to Alaska, although the prime month of migration is in February.

Downtown San Diego across the bay from Cabrillo National Monument
Being up here gave us a real idea of the topography and geography of the region. We could see Cayamaca Peak (the highest mountain in San Diego County) to the east, the snow-capped San Gabriel Mountains north of Los Angeles way off to the north, Otay Mesa and mountains of northern Baja to the south, the Coronado Islands off Baja to the southwest, and San Clemente and San Nicholas island to the northwest.

Hilina catching a breeze by the whale viewing platform

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