Sunday, February 08, 2009
Bedrock stays mostly out of sight under the thick Pleistocene sediments of Puget Sound, but as you walk north among the logs and small dunes toward Rocky Point, basement is rising invisibly beneath your feet, all of a sudden appearing in a series of ledges at the point itself. Then it disappears for a few more miles, finally emerging at the north end of the island for good, forming Deception Pass and all of Fidalgo Island.
These rocks are Mesozoic metamorphics, part of a complex story of crushed and slivered tectonic plates that plays out in the San Juan Islands and southern Vancouver Island.
The bluff above the rocky ledges consists of dirt and debris dumped over the edge, probably the remnants of old clearing and grading on the Naval Air Station (of which this is part). Convenient, though sort of sloppy.