A Piece of the British Columbia Coast Range via the Juan de Fuca Lobe

I came across this small boulder in the sand of Shishi Beach on the west coast of the Olympic Peninsula. My purpose that day was to reach some unusual bedrock outcrops, but this rock got my attention as I used the beach as my route to the outcrops of interest. The boulder is granitic (likely tonalite for hard core igneous people). However, I know of no granitic rocks anywhere on the Olympic Peninsula. This boulder hitched a ride on the Juan de Fuca lobe of glacial ice approximately 18,000 years ago. This lobe of ice extended out beyond the current coast line and this boulder derived from the coast range of British Columbia is a reminder of that period. The distance traveled is a minimum of 120 miles.


I always enjoy seeing rocks like this one as it reminds me of great adventures I had mapping and collecting rock samples within and along the margins of plutons in the British Columbia Coast range and crystalline core rocks of the Washington North Cascades. Who knows this small boulder may be a transported fragment of the Spuzum Pluton or Scuzy Pluton.

Some how this rock was sitting alone on the beach, but there were plenty of similar rocks along the upper beach where the bluff consisted of very boulder rich glacial till.

The boulders in the sand were not the only thing that got my attention. I was not the first to walk the beach that morning. I am assuming an otter, but alas I never saw the creature that made these prints.

Big news out of Quilcene

Oysters at low tide, Dabob Bay with Toandos Peninsula on the right and Bolton Peninsula on the left.

I posted this picture of oyster beds on Dabob Bay at the upper end of Hood Canal before on a post regarding efforts to protect water quality for this very valuable resource. This large oyster crop covers hundreds of acres of tide flats. Last summer my wife and daughter were in Philadelphia. They called from the restaurant to tell me that Washington State Dabob oysters were on the menu. Shell fish are a very valuable Washington State industry.

Last week arrests were made by the Washington State Department of Fish and Wildlife and the Jefferson County Sheriff for theft of oysters and clams from both private and public tidelands in Dabob Bay and Hood Canal. http://ptleader.com/main.asp?SectionID=36&SubSectionID=55&ArticleID=26544
If it is true that theft was taking place, it was at a remarkably large scale and involved what appeared to be reputable companies. For several years my company shared an office building with an office of Washington State Department of Wildlife. I for one have always appreciated the work they do. They have a difficult task protecting our resources.

Diablo Lake Rock Slide

A rock slide slid into the upper end of Diablo Lake in eastern Whatcom County. (I love reminding people that Diablo Lake is in Whatcom County). The slide blocks the access road to the Ross Lake Dam power house.

The slide took place in vertically foliated banded biotite schist and is part of Skagit gneiss complex. This formation consists of very highly metamorphosed sandstone that has been heated pressurized during deep burial during the Cretaceous. These rocks were buried as much as 30 km below the surface approximately 75 million years ago. The rock failure appears to be the result of a combination of vertical foliation with cross cutting horizontal joints. And of coarse the slope is a cliff and gravity and some freeze thaw will cause things to fall down. It won't be the last in this area of very steep slopes.

The Chuckanut Range and Silver Creek Falls after Cole after Hannock

We live in a landscape where waterfalls are very common. They are truly works of art and are worth taking a hike to see. David Tucker’s Northwest Field Trips http://nwgeology.wordpress.com/the-fieldtrips/the-chuckanut-formation/silver-creek-stratigraphy-and-flood-erosion-in-the-chuckanuts/  suugests a great hike to a waterfall a short distance south of Bellingham. This is an outstanding winter hike that I have done twice this winter. David is putting together an excellent series of trips with many in my local landscape and is working on others throughout the state.

Silver Creek is located within what locals call the Chuckanut Range. This is a range of mountains uplifted in a series of folds between Bellingham on the north and the Skagit Valley to the south. Interstate 5 weaves through the range in the only stretch of mountains along the I-5 corridor in the state. The folded Chuckanut Formation creates a landscape somewhat similar to some of the Blue Ridge Mountains in the eastern United States with ridges of resistant sandstone and valleys underlain by weak shale and mudstone. The Chuckanut Range is not a high range by Washington standards, but it is rugged and is unique in that the ranges rises directly up out of the sea along the coast line south of Bellingham. This feature is often emphasized as the only place where the Cascade Range reaches the sea.

Google Earth view of Chuckanut Range between Lake Whatcom and Samish Bay south of Bellingham. Folded bedrock along anticlines and synclines is readily visible.

This rugged corridor between the Salish Sea on the west and the Cascades on the east has been identified by Whatcom County as a habitat corridor and there are a number of ongoing efforts to ensure this area stays undeveloped and utilized as forestry and park land. Those efforts include Blanchard Mountain on the south which will soon have a portion designated as a natural area with the commercial timber lands around the perimeter expanded to remove development risk. Washington State Parks protects significant tracts in the northwest portion of the range. Whatcom County has expanded its holdings within the range with several parks such as Pine and Cedar Lake and Squires Lake and is working with the Washington State Department of Natural Resources towards the creation of an 8,000 acre wilderness park within the Lake Whatcom watershed.

View of Chuckanut Mountain looking west from the slope of Lookout Mountain. Interstate-5 can be seen curving through the valley on the upper right.

Resistant sandstone and conglomerate ridges within the Chuckanut Range.

As for the hike up Silver Creek it ends at a great waterfall. The water flows over an outcrop of conglomerate which breaks the flow up into a very nice visual effect. Additional falls are located above the main falls for those that like to crawl up steep slopes and through thick jungle.
  

The main falls on Silver Creek

The next cascade above the main falls with Sam a dog with remarkable climbing talent. 

 A lovey cascade or a barrier to be climbed

Cascade over Chuckanut sandstone

These falls reminded me of some of my favorite landscape painters and their rendering of Kaaterskill Falls in the Catskill Mountains of New York. Kaaterskill Falls is New York State’s highest with a combined height of 260 feet. I estimate the falls at Silver Creek to be about 90 feet so it is within the same magnitude and there are additional falls upstream of the main falls. Kaater means male wildcat and kill means stream. Cougars definitely live in this area so in that regard there is a link to Kaaterskill Falls as well.

Thomas Cole in particular moved landscape painting to a level that consistently captured the geology of a site and he is one of my favorite landscape painters.

Thomas Cole - The Falls of the Cauterskill, 1826

Stephen Hannock also did a great job of rendering the geology in his painting of Kaaterskill Falls. His paintings have fascinating inscriptions and stories etched into the painting. Looking at his paintings can be like fossil hunting within the layers of bedrock or identifying the source of clasts in the conglomerate at the Silver Creek falls.

Stephen Hannock - Kaaterskill Falls, 2005, New York Metropolitan Museum 

Detail with a reference to Cole’s work and others etched into the geologic strata.

While working on this post I found that my wife Lisa was rendering a view of the Chuckanut Range as most of us usually see it - from the Interstate.

Lisa McShane, 2010, Winter Highway Chuckanuts

http://lisamcshane.blogspot.com/2010/03/winter-highway-chuckanuts.html

Cities and big quakes

Interesting article in the New York Times on large cities in seismic zones.

http://www.nytimes.com/pages/world/index.html

Crazy Weird Erratics make National Natural Landmark Status!

Dave Tucker has a great web page http://nwgeology.wordpress.com/ (also on the Reading the Washington Landscape blog role) with field trips in our area that is well worth taking a look at for trip ideas and understanding the geology of our area. He describes several spectacular erratic rock locations in the area including some of my favorites and a few that I will have to visit. Thanks Dave, this post has been inspired by you.

Erratics are rocks that are out of place. Erratics have been transported by glacial ice to a new location where they are out of place. Erratics can be small, but the big ones seem to capture the imagination of geologists and non geologists alike. My wife Lisa describes the erratics on the Waterville Plateau in central Washington as “crazy, weird”.

I frequently look closely at erratics in glacial deposits on the Olympic Peninsula to determine if the glacial units I am looking at came from glacial ice from Canada or the Olympic Mountains. If I see granite, the odds are the unit was derived from ice that originated in Canada.

The Puget Sound, Strait of Juan de Fuca area and the northern tier of eastern Washington have all been glaciated multiple times over the past couple of million years. Hence, glacial erratics are a common feature in these areas. The most out of place erratics are the boulders that got rafted on ice bergs in the ice age floods that swept out of glacial Lake Missoula across eastern Washington and down the Columbia River. Several very out of place rocks can be observed in the Willamette Valley south of Portland from these flood rafted ice bergs. Erratic Rock State Natural Site is one spectacular example.

Erratic Rock Oregon State Natural Site (photo from Wikimedia Commons) 

Another great spot for erratics is the northern portion of the Waterville Plateau in central Washington. Part of this area has been protected under the National Natural Landmark program. Erratics make National Natural Landmark status! My wife Lisa and I love that area and some of the erratics have been the subject of a series of winter landscape paintings Lisa has done on the Waterville Plateau.

Winter Fields

 (Copyright Lisa McShane http://www.lisamcshane.com/Artist.asp?ArtistID=24358&Akey=G4YBGL8X)

Erratic and the Road

(Copyright Lisa McShane http://www.lisamcshane.com/Artist.asp?ArtistID=24358&Akey=G4YBGL8X)

Despite having observed many glacial erratics, I never get tired of seeing them and have a few favorites. While the erratic pictured below might not be the biggest, its position is crazy, weird.

Erratic ready to be cradled by Bob Bailey in case it falls out of glaical drift at shoreline northeast of Biz Point, Fidalgo Island, Skagit County.

Finding faults with LIDAR

My last post on Sumas Mountain and LIDAR indicated that a fault could be observed in the LIDAR image. So here it is. It is my understanding that the initial LIDAR in this area was done to assess river channels on the Nooksack River and someone noticed a straight line on the image.

LIDAR has proven to be a huge help in identifying faults in western Washington. The glaciation of the Puget Sound region as well as the preponderance of thick vegetation has made identifying surface faults very difficult. The identification of surface faults in the Puget Sound region got a big boost when LIDAR began to be used.
A big break came in 1996 when the Kitsap Public Utilities District funded LIDAR mapping of Bainbridge Island in order to get a better handle on the water resources on the island. Greg Berghoff with the District noticed a line cutting across the south portion of the island in the LIDAR image and notified geologists at the University of Washington. This caused a great deal of excitement because the line happens to coincide with the Seattle Fault zone and indicates that the ground surface had been off set substantially since the end of the last glacial period.

Toe Jam Fault on south Bainbridge Island

The trenching experts came in and excavated trenches across the scarp, pieced together disrupted soil horizons and age dated the off sets with carbon. What they found is probable magnitude 7 quakes had taken place along this fault scarp. While large quakes are known to be a risk in Washington State, this discovery recognizes large quakes in close proximity to large population centers are a very real risk. Hence, the Washington State Department of Transportation simulation of what could happen to the Seattle waterfront and the viaduct is very possible as this fault strand is just a few miles from the Seattle waterfront and fits the description of the type of event that would take out the viaduct.
Another fault appears evident across the water to the southwest in the port Orchard area. Both of these faults appear to be associated with the Seattle Fault Zone. It appears that the Puget Sound region has several fault zones. These zones consist of several fault stands instead of a simple single fault line. It may be that only a few of the earthquakes actually cause surface ruptures that will show up on LIDAR imagery. However, the presence of surface ruptures indicates that shallow quakes are possible and allows for estimation of the size of potential quakes associated with these fault zones.

Scarp off setting drumlins, Port Orchard area

As noted a fault scrap was identified in Whatcom County near the Kendal area using LIDAR. This “new” fault caused some interesting dialog between the local media and geologists at Western Washington University. The Western geologist commented on an Environmental Impact Statement (EIS) regarding development of the Bellingham waterfront. One of the issues they raised was concern about the presence of nearby faults including the newly identified fault near Kendal that had not been identified as a potential risk to waterfront development. Much of the waterfront has been constructed on poorly consolidated fill and significant portions are liquefiable. The Bellingham Herald was highly critical of the comments claiming that the information the geologists provided was “nothing new”. The lesson I took from that is that policy makers and those that influence policy may be aware of a potential large subduction zone earthquake, but are unaware of the risks posed by nearby seismic events on much smaller but dangerous faults located near population centers.
In that regard LIDAR has been a huge help and the Seattle media seems to be highly aware of the risk. Perhaps it helps that the Seattle Fault zone is named after the City of Seattle. That said taking a look at Google Earth should show how lateral spreading due to soil liquefatcion can impact an area.