Monday, July 07, 2014
Sunset Bay is cut into a thick section of steeply-tilted sedimentary rocks. This geologic structure is exposed in the cliffs that surround the bay as well as in the strike of resistant layers on the eroded platform, but it is also seen nicely in the aerial images, as all of the headlands and islands follow the strike of the rocks.
There's a nice sandy pocket beach tucked into the bay. It's protected from the worst of the open ocean by the shape of the bay and the rocks that guard its entrance, but smaller waves spread out regularly across the flat low tide terrace.
The roots of large spruce? trees appear on the lower beach on the south side of the bay near the mouth of Big Creek (not the same Big Creek as the previous post). Since these trees would not have grown in the lower intertidal, there must have been significant subsidence here. At the same time, the marine terrace that is visible on the adjacent uplands suggests long-term uplift. Or at least net uplift. These subducting coasts ratchet their way upwards, the long-term pattern punctuated by abrupt subsidence in large earthquakes every few hundred years.
Posted by Gravel Beach at Monday, July 07, 2014