Friday, February 10, 2012

Hastie Lake

It's not unusual on Puget Sound beaches, particularly on the west side of Whidbey Island, to find maroon and black streaked sands on the uppermost beach face.  They are often just an extremely thin layer and appear to be left by the highest reaches of the swash in sandy areas. These are basically small placer deposits, where wave action (and sometimes wind?) has separated out slightly heavier minerals from lighter ones.  I believe the red grains are probably garnet.  I'm not sure what the black ones are - hornblende, magnetite (I didn't have a hand lens and even if I had, it's been a long time since I took mineralogy).

Most of this southern portion of West Beach - the general name for this northwestern shore of Whidbey Island, - consists of high bluffs, but here the upland surface drops toward sea level.  The county boat launch and the small development immediately north (Whitecap Lane) are actually on a small spit that extends another quarter mile to the north.  At low tide, and in years when beach sediment is thin, there is a well displayed peat bed on the beach containing lots of intact wood.  It is probably the remnant marsh from when the barrier lay farther offshore.  A little farther north at Swan Lake, similar peat has been dated to about 2000 years ago.


I was last here on Veteran's Day (Hastie Lake: November 2011), listening to the wind howl and watching the waves. Today is very different.

No comments: