Sunday, May 12, 2013

Bolton Peninsula Introduction

The Bolton Peninsula is a bit out of the way and a bit off the beaten path. That said part of my purpose is to share a few geologic notes - there are some important geologic features on this not so easy to get to place. By one example there is an active 1,600-foot wide translational landslide calving blocks of soil off of a 200-foot cliff. This area is slated to be mapped by the Department of Natural Resources Geology Division this year so I am motivated to put together some information on the area. I'm excited about the DNR bringing their skill sets, resources, dating equipment and larger picture experience to a land area I know fairly well and want to know more. But I also think the Bolton may have some features that will shed light on a broader understanding of local tectonics and glacial history. 
The peninsula is a steep sided finger of land east of the small town of Quilcene and is located between Quilcene Bay on the west and Dabob Bay on the east and south. The bays are inlets on the northwest side of Hood Canal. The peninsula is approximately one mile across and four miles long. The summit ridge is 570 feet high. Lots of steep slopes for assessing geologic hazards. And those steep slopes also provide excellent exposures to the underlying geology.
Bolton Peninsula with Quilcene Bay on the left and Dabob Bay on the right

As out of the way as the Bolton is for most people, I have had the opportunity to make numerous ventures to the peninsula and have walked its entire shoreline. So for me it has not been out of the way at all.

The Bolton Peninsula is within the Quilcene Quadrangle which is listed to be mapped within the next two years as part of the Washington State Department of Natural Resources Geology Division geologic mapping program. The area has been mapped before by Birdseye (1976). An update and perhaps more detail is warranted as we now have a better understanding of some of the units in the area, LiDAR will help greatly with interpretation of landforms and some technical advances have been made in dating units that were not available to Birdseye. I will say the Birdseye did a remarkable job. Where my interpretations have deviated from Birdseye it has typically been due to level of detail, fresh landslides that exposed units not previously visible, availability of LiDAR and my access to private upland properties.

The southern shore of the Bolton has some unique features that warrant further exploration and interpretation.

Southern end of Bolton

LiDAR southern end of the Bolton

The LiDAR image shows a great deal of detail that could never be deciphered from an aerial image. The smoothness of the upland areas with slight lineal features is the classic uneroded glacial drift landscape with glacial lineations oriented north to south. Not much in the way of recessional outwash from the retreating ice on the uplands of the Bolton. The incised drainages cut into the peninsula are post glacial.

Close up LiDAR of southern Bolton shoreline
The south shore of the Bolton has a great bedrock exposures, tilted glacial and non glacial alluvial units, a massive translational landslide and an ancient river deposit with an intriguing gravel and cobble distribution.

A note about access. The shore is public, but there is no official public access via land. Regardless of public versus private, this is a very cliffy shore. The south bluff is for the most part 240 feet high or more and can only be traversed at a few spots and even those are hairy. I have traversed the ravine shown on the right side of the LiDAR above twice. Both times the experience was horrible, dangerous and uncomfortable, and I am used to nasty brush and slopes. I should also add that poison oak is very present on portions of these slopes. The reality is that if you want to visit the southern Bolton shoreline, you will really need to want to, and I would recommend boat or hiking the beach from the limited access points available (There is some public land that reaches the shore, but I am not clear as to its openness to access).

Posts to follow: Twin Rivers Formation, tilted glacial till, the big slide and the Great Puget River?


Geoff said...

I read an interesting blog like this, and think of Jim Lynch's The Highest Tide. It's about a coming of age boy who finds as much interesting in the water as you do on the land. The adults, the media, and familiar institutions, just don't get it like he does. The land and the water each have their own story, if we take the time to observe, listen and figure it out. Nice.

Anonymous said...


This is an interesting introduction to the Bolton Peninsula. I am looking forward to reading more. Have you looked at the faulting Birdseye and Carson (and Bretz) report? I can’t wait to take a look at those locations.
Trevor said...

seems like a boat would be the way to go. all of the beaches are public here? I'm curious how you know this. I always have trouble discerning public/private beaches.