Tar balls on Coastside beaches caused by natural seepage

Those tar balls washing up on Pacifica and Coastside beaches for three days this week turned out to be the result of natural oil seep carried on the current from Southern California reports the County Times.

A number of tar seeps dot the coastline of Santa Barbara County, particularly around Goleta and near Point Conception, he said. The oil seeps represent the shallowest tar deposits along the Monterey formation, an underwater ridge line of brittle rock that formed between 23 million and 5 million years ago, according to Lorenson.

The plankton that formed fossils in the rock have, over time, been exposed to pressure and pushed to the surface by the movement of the Earth.

The USGS has a "fingerprinting" test that allows scientists to distinguish between the provenance of various natural tar seeps. In this case, however, Lorenson said, they may never be completely sure of the source.

"The size of the tar balls can be rather large. That’s a characteristic of the tar balls that come from Point Conception," he said.