Geo 365: Feb. 13, Day 44: Sunset Structures

On the north shore of Sunset Bay, numerous faults cut the marine terrace- these are even apparent in the FlashEarth view! The cross hairs in that location are approximately where I was standing when I shot this photo, looking to the north west.That image was captured between high and low tides; we were here intentionally for a negative tide- a tide lower than the mean of the lower of the two daily low tides. If you want to enjoy the tidal zone, whether it's for geology, biology/tidepooling, or simply sight-seeing, you need to pay attention to the tide tables. Numerous examples are online; here's the source I tend to use. Negative tides give you an opportunity to get to lower areas, and spend a bit more time in them. Also, pay close attention to the time of the minimum, and when that time passes, start working your way back towards higher ground- no need to rush, just be aware that the ocean is now coming at you, and can easily trap you in a dangerous or fatal spot if you don't pay attention.

Above is an annotation of the top photo, showing a major fault and a minor subsidiary- again, these are plainly visible in the FlashEarth view. A single prominent, resistant, bed of sandstone has been split into three slabs, which rise above the surrounding terrace. The flat ground surface of the bluff top suggests an older, raised terrace, and the horizontal sediment below it helps confirm that. It's not clear to me whether the term "angular unconformity" is reserved for structures where all the components are fully lithified. If it is, the above is a "fake" example of an angular unconformity.

Photo unmodified. March 8, 2012. FlashEarth Location.