Tuesday, December 13, 2011

Island of Shells

Ignore this post if you are only interested in Electronic or Ham Radio.

This post is Way-Off-Topic for my blog, but I want to record my observations for others to review.

About ten years ago, while cursing Puget Sound looking for interesting islands and shores to anchor, explore, and spend the weekend. I found an very interesting exposed cliff on the end of a small Island.

I took photos and have always wanted to stitch them together to create a large composite, I may yet if I find the photos.

The following is my recollection of what I saw.

The exposed cliff appeared to have been shaved, cut, or eroded off of the narrow end of the island, exposing a cross section of the layers that make up the island. The cliff rises about 60 feet from base, near the current shoreline. The width of the base is maybe 200 feet.

What I found most fascinating was the obvious eons of the exposed time. There are evidents of about fifteen different shorelines, each with its own population of different types of shells, or the lack there of.

All of the layers get thinner as the layer gets closer to the center of the island.

The oldest (lowest) shoreline contain the most shells, with corral, cockles, and scallops among the items found. The shells appeared thicker than any on the upper layers. Near the current edge of the island this shell layer is about 20 inches thick and containing mostly just shells. The low end of this layer is exposed near the shore by current wave action.

Above the first layer, is a band (maybe 10 inches) of sand, it appears to be volcanic ash, without shells, or any signs of life.

Then another layer (maybe 6 inches) of different type of sand, with only short spiral shells, maybe from a tube worm?

The previous two layer types repeat a few times, with different thickness.

Above that, layers contain an obvious shoreline and associated seashells, but if I remember correctly they were different than any found in lower layers. Their shells appeared to be much thinner.

Each layer of the cliff is text-book cross section of what I would expect of a seashore.

New shorelines appeared to raise in major steps, as the successive layers move up and inland toward the center of the island.

This type of shoreline repeats, several times, up the outer edge of the narrowing cliff, with each successive shoreline further up and inland.

The top of the cliff is the current soil and vegetation layer which is about 60 feet above sea level, it appeared to be about 2 feet thick on top. This top layer is thinnest low on the sides near the water (sea level).

What I find interesting it appeared the island grew from top down (i.e., it was NOT pushed up) and therefore the shells that are most readily picked up, at the foot of  the cliff, are the oldest, and yet they appear to be in perfect shape. If the island grew from the top (as new soil is deposited) then that implies (to my untrained eye) the Ocean and Puget Sound was once as much as 60 feet higher. Again implying, the oldest shells are maybe very-very old.

Yet,  maybe the island sank in jumps, laying new sediment over old and changing the shoreline, and then was pushed up to the current height over a very short period of time. But I do not think so, as the shelled cross sections of the shorelines would not have the same distinctive shapes.

This island is a Sheller's Paradise, with perfectly shaped very-old shells to be easily found.

I think this is one of the most interesting island of Puget Sound.

The island is a semi-popular boaters-only destination, but I do not think many people understand what they are seeing.

I plan to release the location of this island, if I find someone with credentials and interest enough to explore and date the layers. But, so far I have not found that person, and I have avoided any disclosure of the islands name to avoid plundering.

If I find the photos and able to stitch them together, I will post them with a link back to here.

So,  now back to - Electronics, Ham Radio and On-Topic.


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