By Joe Eskenazi
What would it take to rezone 19th Avenue as “beachfront property”? I conjectured it would take an asteroid hitting just off Ocean Beach. But Toby Garfield said it would take far less than that — and since he’s a Professor of Geosciences and Oceanography and an expert in wave mechanics, let’s go with his diagnosis.
“No, we do not need an asteroid. A huge earthquake on the San Andreas Fault [or] a huge mudslide down one of our canyons could generate a significant tsunami,” said the professor.
“In fact, one of the largest tsunamis we know of in the Pacific was in 1700, when an earthquake caused a cliff in Oregon to fall into the water and a tsunami devastated a large part of Japan. So it is real. It could happen. Of all things you can worry about, add that to the list.”
Garfield lectures to large crowds in his courses at San Francisco State, but it’s a good bet…
that his students aren’t toting around bottles of beer and plus-sized glasses of red wine, as were many in the packed-to-the-rafters audience he recently addressed in Potrero Hill.
And it wasn’t just your humble narrator who had a chance to query the expert; this was part of the “Ask a Scientist” series often held at the Axis Café, located, maddeningly, at the intersection of 8th and 16th Streets (hopefully, “Ask a City Planner” is coming soon).
The No. 1 query: How the hell do the waves just north of Half Moon Bay at Mavericks get so damn big? The answer? Steroids, of course.
Well, that’s what Nic Foit and Ira Tes told me.
Actually, Mavericks is the Mecca of surfing thanks to the old real estate agents’ adage: “Location, location, location.” As you can discern via a glance at the pretty, color-by-depth illustration created earlier this year by scientists at CSU Monterey Bay, the sea floor’s gradual ascent approaching Half Moon Bay acts as a wave-generating ramp. Yet perhaps even more importantly, the undersea rock formations near the highlighted area serve like powerups in a Mario Brothers game.
The underwater barriers rapidly shunt the energy of a 100 meter-wide wave into a focused, 10 meter-wide channel and, voila! You have a 50-foot-high wave that surfers are dying to ride (sometimes literally).
Grant Washburn is one of those surfers — but, in his work with scientists like Garfield, he’s also become “an instrument” in their wave experiments. And, when asked how much more energy is contained in a Mavericks-sized wave than the five-foot variety that crashes, harmlessly, to the shore on Ocean Beach every day, the physicist and the surfer took different approaches to the query. Garfield broke out a little freshman-level science. Washburn went anecdotal, noting that wiping out is like “driving into a brick wall” and can keep you pinned underwater for two minutes or more.
Garfield pointed out the energy in a wave augments as the square of the height. So a 10-foot wave has four times the energy of a five-foot wave and a 50-foot Mavericks monster has 100 times the punch (those register on Berkeley seismographs when they hit the beach, incidentally.).
When questioned by an audience member why big wave surfers never seem to “ride the curl,” Washburn deadpanned that “These waves are really scary.”
Inadvertently paraphrasing a line from Danny Vermin in “Johnny Dangerously,” Garfield added: “You could ride the curl — once.”
Watch Garfield and Washburn in a KQED video on wave science here.