– Start and finish at 16th street and Misson street.
– Headed down Mission to Clarion Alley, took a right up to Valencia.
– We then turned left down to 18th street and turned right.
– We followed 18th to Dolores Park and grabbed ice cream at Bi Rite Creamery.
– Ice-cream in hand we were told to think about elevation and sidewalk changes as we walked the next few blocks
– We then travelled back on Dolores to 16th street and turned left toward Corona Heights and the Castro.
– We crossed Castro and walked up 16th to the top of Corona Heights stopping to meet geologist Christopher Lewis at Flint.
– Ice-creams no longer in hand.
– Chris took us around the hill top to see different views and left overs from earthquakes indicating geological movement as well as rock outcroppings to better illustrate what he was explaining.
– He explained the view we saw from the top of the hill illustrated where faults exist by tracking where hills came up from flat. For example the hills we looked at across the bay start at the Hayward fault.
– He briefly spoke about the past topography of the Mission district (with a lake, and how Mission Creek used to rune straight through the middle, and most importantly that the mission was marsh land that led to the bay.)
– He told us the two main environmental hazards in California were landslides and earthquakes, but knowing the past topography of the mission, soon with rising sea levels flooding will also be an issue.
– He then explained that the street names are embossed on the corners so that people can navigate in a catastrophic situation. (Post 1989 Urban Plan)
– We talked about how much of the city is built upon fill, sunset and marina are on sand, while much of the Mission, Embarcadero, Soma, Bay View, and Hunters Point are landfill.
– He then set into the rock that dominantly exists in SF. Mostly mesozoic sedimentary and Serpentinite (California state rock), all of which is oceanic and originated on the sea floor.
– Explaining further that sedimentary chert is old sea floor compressed shells and debris, while Serpentinite is ocean cooled mantle. [Mention of Pulgas Water Temple in south bay and Sunol Water Temple in east bay.]
– He showed us the side of the sedimentary rock we were in front of to display a fault that was uncovered by quarrying in the area many years ago.
– Went on to explain how 280 highway and skyline (highway 35) trace the San Andreas Fault, the fault moves offshore north of there in Pacifica, and back on in Bolinas following up through Tomales Bay, Dog-patch and Potrero Hill are Serpentinite outcroppings.
– Last tie bit: Rip wrap in surf at ocean beach contains old tombstones from cemeteries moved to Colma in the 30s and 40s.
– We then followed the same path back to 16th and Mission.
Observations and Notes Taken by Timothy Kopra. Edited by Sebastian Alvarez.
Thanks to Christopher J Lewis. Chair, Earth Sciences Department.