There’s a beach that shines gently in my memories. (Cairns #59) During my first hitchhiking trip after college, a driver wanted to stop and visit a beach he really enjoyed. We walked down to a beach where the sand occasionally shimmered with fragments of abalone shell that had been wonderfully rounded and polished by the surf sand. Fundamental to that beach memory was its backdrop: nearly vertical slabs of strata tilted to face the ocean. There would be a long stretch of a pure grey rockslab cliff defining the back of the beach and then further down, the next strata layer would define the backdrop of the beach with a slightly different color for the next stretch. The upright rock slab cliffs created such a clean, simple, elemental sense of place, it felt like a setting for a Noh drama.
Alysia and I went on a week’s vacation along the coast and I wanted to show her that beach. But it wasn’t the same as in my memory. Of course, memories can simplify and improve over forty-five years. But as I studied the beach, a more interesting hypothesis formed.
The far end of the beach did have the beach-defining backdrop of tilted strata. But most of the length of the beach was steep eroding slopes with some small trees and other vegetation able to root on it but with no defining sign or shaping of bedrock. That entire long section was the part that didn’t match my memory.
Here is a picture at the contact between the two sections. To the left, a succession of firm, tilted strata. To the right, looser, less-consolidated strata. The beach changes character right where the last slab strata disappears. Those slab layers are like a giant retaining wall that the ocean is slowly eating away.
The next photo looks at this contact from the other direction. Notice that the beach ends only a foot or so back from where the last slab of strata would run if it extended on.
My hypothesis is:- that forty-five years ago, those last couple of layers of tilted strata extended the length of that beach, creating the clean retaining wall backdrop of my memory.- that during the last forty-five years, wave erosion chewed its way through the last foot or so of the remaining hard strata that formed that retaining wall. As that wall crumbled away, the loose materials held behind it slumped down and plants started growing on the now rootable slope.- as a result, the main stretch of beach now has a completely different appearance.
We tend to assume the time span of the small, incremental changes we associate with geologic change happens over a completely different scale than from a human’s life span. That assumption can act as a buffer that dilutes our response to sinking aquifers, declining insect populations, climate change, . . . . But that magic beach was, I think, revealing that our lives fit well enough within that time scale to both influence and be influenced by the small incremental changes that shape our planet.
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