Taking a Strike and Dip — in Strawberry Canyon

Georgia Wright - July, 2010

A geologist at the Lawrence Berkeley National Laboratory recently argued with Professor Garniss Curtis that the rock of the hill upon which the Lab sits is not dipping west toward the dorms but east or north. So Garniss, armed with a geologist’s fancy compass which includes levels and a gizmo to measure angles, and I drove to the Foothill Parking Lot above the dorms, where the exposures of sandstone and shale are now covered by a web of concrete, evidently to keep them from sliding — west.

Garniss worries that in the expected large quake on the Hayward Fault, the volcanic caldera, pressing on this slope, may cause it to slide onto the dorms.

We walked a short ways up a road beyond the parking lot and found an exposure of layers of shale, common in this area. Garniss measured the "strike" across the bedding plane of the shale.

Then he measured the dip, the angle at which the beds are canted. At 40 to 50 degrees, this was steeper than he had measured years ago.

Garniss (age 93) insisted we continue up the extremely steep road towards the Lab perimeter to look for more exposures. Dragged along, I (age 73) was at least pleased to spot a two-pronged buck (younger than I) standing in the road. The buck and I admired each other’s stamina until he stepped with dignity into the brush.

We found no more bedded exposures, only sandstone you could reduce to powder between your fingers, but we hiked up to the “Big C”, just below the Lab fence, and stopped to drink in the view, that view which appears to be one important reason the Lab holds so tightly to this dangerous site.

Now we have some evidence for the dip and its direction, but the Lab geologists are arguing about the presence of an old volcanic crater — a "collapse caldera". According to Garniss, this caldera is composed of crushed and deformed volcanic rocks, mixed with large amounts of ash and volcanic debris, as well as being clay-rich and unconsolidated. Where do the Lab geologists think all those volcanic stones (basalt, andesite, tuff, and “Moraga volcanics”) came from?

Garniss considers the unconsolidated mass of old volcanic rock from the caldera to be very dangerous because it presses on those bedded sandstones and shales aimed at the dorms. If an earthquake occurs when these beds are soaked with winter rains the chance of a major landslide are great along the slippage planes of shale which are dipping westward.

• Dr. Garniss Curtis, Professor Emeritus of the Department of Earth and Planetary Science at UC Berkeley, sent a letter in 2008 to the UC Regents explaining the unstable geological conditions of the hills to the east of the campus and strongly recommending that "Major buildings of any kind should not be constructed in either of these canyons bordering this huge block of unstable rock." Read it here.


• Dr. Curtis explains the geology of Strawberry Canyon and the dangers it presents in our two videos.


• See other documents concerning Strawberry Canyon.