In the last few weeks, some sticky blotches of a black tar-like substance have been appearing on several beaches in Laguna. Many people assume that this phenomenon is being caused by industrial pollution associated with the extraction, transportation and storage of petroleum.
In fact, as much as 50 percent of it is naturally caused by oil slowly escaping through networks of capillaries, fissures and vents from underground sources found offshore within the continental margin of the California coast. Being lighter than water, it floats and some of it is eventually carried to shore by the tides, currents and wind. As the oil degrades in the salt water, it becomes sticky and more viscous, ultimately forming a black, tar-like substance called asphaltum.
The seeps are not just an offshore phenomenon but occur on land as well. There are thousands of seeps in California, and one of the most famous, the La Brea Tar Pits in Los Angeles, has a museum built around it.
Oil is formed by the decay of organic matter that has been buried under sedimentary rock and exposed to heat and pressure. Millions of years ago, California was more mountainous than today. Organic material such as dead animals and plants was carried to the ocean by water, rocks and gravity until reaching the ocean where it mixed with zooplankton and algae, eventually settling on the sea bed. Over eons, more and more sediment got deposited ultimately forming layers that held the decomposing organic matter. Exposed to heat and pressure over time, this material turned into oil.
Today, much of the ocean floor off the coast of California is made of porous sedimentary rock, such as shale, sandstone and limestone, that holds an abundant amount of oil. Although natural seeps are episodic and can lie dormant for long periods, seismic activity such as earthquakes can affect flows. There are over 50 catalogued natural oil seeps between Point Conception and Huntington Beach with the world’s largest being Coal Oil Point in Santa Barbara.
Archeological evidence indicates that asphaltum from oil seeps was used thousands of years ago by prehistoric peoples. In California, Native Americans used asphaltum as decoration, as an adhesive and for waterproofing on their weapons, baskets, brushes, boats and tools. It is believed that early California settlers used it to lubricate the wheels of their wagons, as waterproofing and as lamp oil.
In fact, observing oil seeps led to much of the early petroleum discoveries in California, and many of the first wells were drilled in areas where seeps existed.
In February and March of last year, there were reports of dozens of seabirds, mostly Common Murres (Uria aalge) needing rescue along the coast from Newport Beach to Malibu because they were covered in oil and tar that is believed to have come from naturally occurring offshore seeps.
The seeps have both immediate and long-term environmental consequences that are still unknown. Not only is there toxic sediment contamination around the seeps, other pollution effects include water quality degradation, greenhouse gas (methane) emissions that contribute to global warming, and dangers to marine wildlife, as well as gooey, sticky tar-like substances on the beach. Should you come in contact with tar on the beach, the gentlest way to remove it from skin is by scrubbing with cooking oils, soap and water and if it persists, using nail polish remover or a pumice stone.
Mia Davidson and artist Jan Sattler are long-time Laguna residents and year round ocean swimmers who believe that educating the public about the marine environment will contribute to preservation of the habitat and its organisms.View Our User Comment Policy