Taking a Streetcar to Subduction : Professor Points the Way to San Francisco’s Geologic Past

“Are you out measuring the city? Is the elevation still as it was yesterday?” asked Josefine Thunig, 62, as she encountered her friend, geology professor Clyde Wahrhaftig, 67, on a streetcar.

Wahrhaftig, silver-haired with flowing silver beard, smiled shyly and returned his friend’s greeting.

“We have been bumping into each other on this streetcar for 15 years,” said Thunig, a financial analyst whose husband, Herman, is a watchmaker.

“I thought that he was a zoologist,” Thunig said. “The first time I spoke to Dr. Wahrhaftig I asked him where do the squirrels sleep at night, in the trees?”

Thunig said the professor replied: “I don’t know. I’m a geologist. Ask me about the rocks.”

Wahrhaftig divides his time these days between UC Berkeley, where he is a professor emeritus, and Menlo Park, where he is involved with the U.S. Geological Survey in producing a map and report on the history of the Ice Age in Yosemite.

He spent years in Alaska generating government reports, books and maps of the geology and coal deposits of the Alaska Range and has written numerous scientific papers on the geology of California. He is co-author of two text books, “The Earth, an Introduction to Physical Geology” and “The Earth and Human Affairs.”

But he is best known in the Bay Area as the author-illustrator of “A Streetcar to Subduction,” a guide to San Francisco’s bedrock formed at least 100 million years ago. In his guidebook, he takes the reader by bus and streetcar to fascinating rock outcroppings throughout San Francisco.

Wahrhaftig’s enthusiasm for public transportation is easily explained. He doesn’t drive. “When I was a teen-ager my father, a doctor, had to repair too many of my schoolmates involved in automobile accidents and would not allow me to drive,” he said.

“In college I was too poor to afford a car. Where I worked in Alaska there were no roads. I soon realized the advantages to health, safety and sanity in not knowing how to drive. I have always managed to get around on foot or by public transportation.”

Wahrhaftig lives in a cottage perched on a rock outcropping not far from the “J” line or what he calls the Streetcar to Subduction. The lot for his home was formed over 100 million years ago of shells of microscopic one-celled animals and red dust blown from the deserts of the world that settled on the ocean floor to form siliceous ooze. That ooze hardened into a rock called chert that outcrops in much of San Francisco. The hardened ooze under Wahrhaftig’s home, he observed, probably originated somewhere between San Francisco and Hawaii.

Wahrhaftig boarded a “J” line streetcar to ride to an exposed pale green rock outcropping, “an excellent example of serpentine. Of course we’re only seeing the tip of the iceberg here. This is part of a band of serpentine that juts as high as 20 feet above the ground, is one half mile to a mile wide and runs eight to nine miles diagonally across the city,” he said.

The professor noted that serpentine, California’s state rock, was originally a rock near the top of the earth’s mantle. Sometime during the geological process known as subduction it got squeezed upward to be mixed in a large slab with part of the ocean floor sediments.

When it was formed, the now outcropped serpentine was buried deep beneath the earth’s surface, said Wahrhaftig. Was it here on this spot originally?

“There was no such thing as here then,” he replied. “The various rocks you see in San Francisco today traveled to where you see them from distant places.”

From the serpentine outcropping, Wahrhaftig boarded a bus for a ride to a fine example of pillow basalt from an ancient ocean floor. Pillow basalt is a bulbous mass of once glassy frozen lava.

He pointed out a great sandstone cliff on the east side of Telegraph Hill and numerous other rock formations around the city.

The professor explained his unusual last name. “It’s German. In German it means: really? I must have had an ancestor running around saying: ‘Is that so?’ ”

His book, “A Streetcar to Subduction,” was published in 1978 for the meeting here of the American Geophysical Union, the largest organization of earth scientists. A revised edition that sells for $7.50 was published by the AGU in 1984. The cover of “A Streetcar to Subduction” shows a drawing of a streetcar being crushed by two geological plates.