This page is referenced by:

• 1 2018-07-16T20:24:26+00:00 Geologic Substratum 19 plain 2018-08-13T15:12:30+00:00

   

  For an extremely large percentage of the history of the world, there was no California…. Then, a piece at a time—according to the present theory—parts began to assemble. An island here, a piece of a continent there—a Japan at a time, a New Zealand, a Madagascar—came crunching in upon the continent and have thus far adhered.
  John McPhee, “Assembling California”
   
  …the change from subduction to side-by-side sliding disassembled the fossil subduction zone to produce the fault-splintered Southern California geology that we see today. That may seem straightforward, but, as we’ll see, the details get a bit involved (76).  In the baseball movie A League of Their Own, the coach (played by Tom Hanks) berates one of his players for complaining that the game is too hard. “It’s supposed to be hard.,” he yells. “The hard is what makes it great.” California geology is hard. The state is a geologic train wreck of rocks, faults, and moving plates, still growing in adolescence (88). 
  Keith Heyer Meldahl, “Disassembling Southern California”
  
  The Palos Verdes Peninsula has a complex, widely-studied tectono-metamorphic history involving cycles of erosion, re-deposition, subduction, and uplift. The peninsula is a tectonic fault block of seafloor sediments and volcanics draped atop a submerged mountain of metamorphic rocks that began rising out of the Pacific Ocean 1.5 million years ago. It is situated in a subduction zone shaped by the interactions among three tectonic plates.
  
  Between 35 and 15 million years ago, as the Farallon Plate subducted under the North American Plate, the Pacific Plate began side-sliding along the San Andreas fault, dragging rocks west of the fault northwest for several hundred miles. These developments caused the clockwise rotation of the Western Transverse Ranges Block (comprising the mountain ranges around Los Angeles, with their rare east-west orientation), and created a stretched zone where rocks that once were buried miles deep in the Farallon Plate subduction zone bobbed to the surface. The metamorphic core complex on which the Palos Verdes Peninsula (and Catalina and the Channel Islands) rests, composed of rocks called the Catalina Schist, was dragged deep into the Earth on the sinking Farallon Plate, then uplifted and eroded, and later dropped to deep ocean depths, to catch the Monterey Formation 8 – 15 million years ago. However, as geologists are quick to caution, “This is only the simplest scenario. At least 150 million years of geologic history is missing on Palos Verdes Peninsula” (Morris, 2000).
  
  In order to probe the depths of geologic history, Pierre Jardin constructed a Palos Verdes Time Portal. Peering and passing through it, he susses out suppressed time, and watches a three million year history scroll by, during which Palos Verdes rises from the ocean in a series of tectonic uplifts, punctuated by pauses, during which new coastlines form.
  
  This happens at least 13 times, as evidenced by the past coastlines visible today as marine terraces, platforms carved by waves which are then uplifted to form land. The tectonic uplift pushing up the terraces, produced by compressive stresses in the plates, works in tandem with climate cycles that cause sudden shifts in sea level.
  
  Human history inscribes itself in this story in the form of the housing developments sited on the terraces, which then caused landsliding, or mass wasting, the movement of rock pulled downwards by gravity. Irrigation sped landsliding because it changes tuffaceous layers in the strata to a slippery clay which fails easily when wet. In May 2012 a large swath of road and cliffs fell into the ocean in the White’s Point Landslide. The precarious position the shifting grounds of Palos Verdes geology place humans in is dramatically illustrated by the many homes atop eroding cliffs one glimpses from the beach below, fragile temporary dwellings perched above deformations from plate tectonic stresses visible in sharp folds (synclines and anticlines) in the exposed sediments.