Tuesday, December 17, 2013

Discovery Bay Bluff Notes

While checking the lower part of a very high bluff on Discovery Bay a bit of what might pass as modern art of some sort. 

Rivulets of silty water flowing from the silt units down through fractures behind the the bluff face. When the fractures fail the silty rivulet traces are exposed in a complex pattern.

The bluff geology here appears to be possibly marine tidal units with lots of alternating sand and silts and occasional carbon rich silt to clay units a fair bit older than the last glacial period.

While checking out the rivulet patterns I notes small insect burrows in the compact sand. Clearly something stuffed inside the lined burrows that have subsequently become exposed as sand grains fall out around the burrows.

 I was not able to figure them out, but suspect wasp burrows with an old dinner for eggs that hatch in the burrow.

And yes it was sunny as I was in the lee side of the Olympic Range. A few miles south was socked in with clouds and drizzle.

Looking south down Discovery Bay


Kat said...

Did the rivulets follow roots from the vegetation above and outward from the present cliff location?

Dan McShane said...

In this case the water tracks were not associated with roots.

Kat said...

Not arguing, just very curious--how do you know roots weren't there originally? What would I look for if I saw something similar to know whether the trickles were following root-holes or not?

Dan McShane said...

good question. Typically the roots leave a bit of carbon behind and will also alter the soil around the root via pH or oxygenation changes. What I don't understand is why the silty/clayey rivulets lefts such distinctive tracks.