Debris Flow Risk

Two amazing warm sunny days in a row in November. I managed to get out in the field on both days; yesterday Whidbey Island and today a trip up the Nookasack River Valley in Whatcom County.

Tree clearing on alluvial fan

On the way up the Nooksak I took a look at the debris flow creek I posted about HERE and HERE. I was a bit surprised to see that land was being cleared adjacent to the creek on the alluvial fan. Large trees can do a very good job of stopping debris. The trees act a rake capturing logs within the debris flow. Hence removing large trees from an alluvial fan can significantly increase the run out distance of large wood increasing the risk to homes further down the fan that would otherwise not be at risk from large woody debris.

Large wood from debris flow stacked against trees. 

An Erratic Revealed

I spotted this glacial erratic just starting to be revealed by erosion along the shore of Hood Canal. This erratic is a block of the British Columbia Coast Range Batholith, one of the largest granite-diorite magma areas in the world. Think of Yosemite and the granite cliffs there and you have a good picture of the geology of the BC Coast Range. The big melt that caused these magma bodies to form took place between 75 million and 100 million years ago.

The BC Coast Range is a high range with lots of deep winter snow and many glaciers and ice fields. Those ice fields expanded and flowed south into the Puget Sound area and the Strait of Juan de Fuca several times over the past couple of million years. The last glacial advance took place between approximately 20,000 and 14,000 years ago. The flowing ice carried blocks of granitic rock like this one to Hood Canal. Erratics are a common site along the shorelines where the fine silts, clays and sand are washed away leaving the boulders behind on the beach. I spent some time working in the BC Coast Range traversing the margins of plutons and batholiths and always like seeing rocks from that area scattered on Washington beaches. Almost like seeing old friends as they bring back memories of good geo adventures.

Geology Field Work and Weather Monitoring

We are entering the time of year where it is highly advisable to keep close tabs on the weather when planning field work. Besides avoiding hazardous weather part of my work is assessing geology hazards and big storms and geology hazards are very much linked. So I routinely check nws.noaa.gov, weather.unisys.com and Western Climate as well as cliffmass.blogspot .  I do as much if not more field work in the winter as I do in the summer. The mild western Washington winters generally do not preclude field work, but it is a good idea to keep an eye on the weather reports while planning ventures on steep slopes or in the forest.

From a safety perspective several weather issues come up in doing my geology hazard work. A primary issue is wind. It really is not a good idea to be in the forest during a wind storm. I lived in Kennewick, Washington while in high school where winds of 80 mph are not uncommon. A little 40 mph breeze was not a reason to not go for a run - not particularly pleasant while running into the wind but great mile splits when it was at your back. But Kennewick is not forested. When I moved to Seattle I would go running in Ravena Park or along the winding paths at the north end of Capital Hill. Running through Ravena Park during a wind storm was a lesson that I have not forgotten. Besides limbs falling the ground was moving as the trees were being tilted and the roots were pulled upward.

Another issue is snow. I love snow but it presents two problems. Access to sites with steep roads gets harder and a covering of snow makes it difficult to figure out the geomorphology.

Deep freezes can pose a challenge to digging hand dug test pits. Frozen saturated soil can be very difficult to dig through after a week of sub 20 degree temperatures.

As for rain that is part of the routine of living and working in western Washington, but I do try to time the Pacific fronts - sometimes to stay dry but there are times when I want to actually be out when a big rain storm hits. The fact is much of our landscape is shaped not by typical storms but by the big storms. Two winters ago I was working on a project in the coast range of Oregon where high water levels in the river canyon and its tributaries had caused approximately 70 millions dollars of damage. The river did not have a gage station. I managed to time a storm hitting the area perfectly and hiked up the canyon during a period when 5 inches of rain fell in 8 hours. It was like working in a bathroom shower. I came away with a much better understanding of the river and a lot more confident in my interpretations.

So this time of year I begin looking at the National Weather Service web site a lot more frequently and pull up long term weather models at the UNISY site. Cliff Mass is always good for proving an earlier warning if something big might be developing. And I try to be flexible with my field schedule and let clients know that field plans are subject to change. Northwest Washington is subject to occasional very cold winds with Arctic air flowing out of the Frasser valley just north of the border. For drilling projects, I know that drillers appreciate a warning if a hard cold northeast outflow wind is expected. Even if they don't bring warm enough clothes, they can't say I did not warn them.

I posted this picture of an approaching weather front before.

This storm caught me off guard. 

I had not been tracking the weather while traveling.

Adakite and Tamanowas Rock (Chimacum Rock)

Adakite at Tamanowas Rock

Adakite is stretching my knowledge of volcanic rocks. Magmatists like using more than three names for lava and have moved well beyond the simple basalt-andesite-rhyolite terminology those less versed in lava use. Magmatists are like Eskimos talking about snow when it comes to magma.

David Tucker sent me an abstract by Hahn and others (2004) regarding adakite at Chimacum Rock. Before I proceed I will note that I will call Chimacum Rock Tamanowas Rock for the rest of the post. Tamanowas Rock is located just west of Chimacum on the ridge between Chimacum and Anderson Lake. Tamanowas Rock is a sacred place to the S’Klallam Tribe. Out of respect, please refrain from hammering chunks of rock off of the formation. The property is open to the public, but ownership requests a "leave no trace" ethos.

I was vaguely aware that Tamanowas Rock was not the more typical basalt one sees on the Olympic Peninsula as part of the Eocene Crescent Formation. I had even stumble across some unmapped notably non basalt outcrops on the forested slopes above the southeast end of Discovery Bay. Schasse and Slaughter (2005) and Whetten and others (1988) both indicate on their maps the presence of dacites and associated sediments near the southeast part of Discovery Bay and link those rocks as being the same as that at Tamanowas Rock area. The nuances of lava were not my primary concern as I was mostly focused on some tricky slope stability problems in the area.

I had never stopped to gander at the bedrock exposed along the Anderson Lake Road south of Tamanowas Rock or ventured to Tamanowas Rock itself, a cliff rising up out of the forest west of the town of Chimacum. So earlier this week, I took a little non work geology field trip to take a look.

Site can be accessed via trials out of Anderson Lake State Park

 or at the close road indicated on the Google image

Analytical work by Hahn and others (2004) (See Here) indicate that the Tamanowas Rock has adakite like traits and point out that the presence of adakite at Tamanowas Rock may be used to have a better understanding of how the ocean plates off of Washington were subducted during the Eocene as this was a period when North America was overriding an ocean spreading ridge. The presence of adakite may be related to the location of the mid-ocean Kula-Farallon spreading ridge at the time. The significance of adakite is that it is very unlikely that Tamanowas Rock is associated with lava segregation associated with the Crescent basalts. At least that is what I think the magma folks are saying. A summary/overview of adakite melt formation by Castillo (2006) can be found HERE.

Regardless of how well versed you are on adakite, a short hike to Tamanowas Rock provides a fantastic exposure of the adakite lava and volcanic breccia. I was a bit pressed for time so I did not take in all the rock exposures, but I also did enjoy the great view from the summit.

Volcanic breccia consisting of adakite blocks

Breccia exposure

View from the summit to the northeast and Admiralty Inlet

The crane is at the naval base on Indian Island

The grassy slopes of the west shore of Whidbey Island are in the distance

While on the summit of Tamanowas Rock it is easy to see that this would be a place of pilgrimage for not only people to today, but would be a special place for First Nations peoples. The S’Klallam Tribe considers the site sacred. According to tribal elders, travelers from great distance would make a pilgrimage to the summit with nothing but a supply of water and fast for three days seeking inspiration.

Use of the site is currently in flux. The back, west side of the ridge abuts Anderson Lake State Park and can be accessed via a foot path that leaves the park to reach the summit of the rock. The property has been in private ownership for many years. Zoning and lots are such that up to a dozen homes could be built on the slopes around the rock including homes on the summit area itself. Property in the immediate vicinity of the Rock was bought by the S’Klallam Tribe. The Tribe hopes to sell the land with a permanent conservation easement that would preclude development of the property. The Rock itself and the land to the east, a total of approximately 60 acres were purchased this year using a loan from the Bullit Foundation to the Jefferson Land Trust combined with private donations and contributions from the S’Klallam Tribe. The loan is to be paid back in two years and is currently being held by the Land Trust.

All together there are a number of players involved: The Jefferson Land Trust, The S’Klallam Tribe (Jamestown), Washington State Parks and Jefferson County. At this point in time final exact ownership is uncertain and as well as management. It will be an interesting management plan to transition from a private land that was routinely used by recreationist including rock climbers to a property managed with public access consistent with the significance of the sacredness of the site and the goals and policies of the entities involved in preserving this landscape feature.

Orcas on the Port Townsend to Keystone Ferry Run

Two Orcas with Whidbey Island in background

I had a good two day trip to the northwest side of the Olympic Peninsula. Besides the good fortune of the Olympic Mountain rain shadow that allowed for dry work and even sun despite the rain most everywhere else in western Washington, the work was good and I even did a little non work geology trip I'll write up on another day.

Had a special treat on the ferry run from Port Townsend to Keystone. A pod of Orcas were crossing our path. It appeared there were at least a dozen. The ferry had to slow for a bit to let them pass as they were in our direct path. I ride Washington Ferry boats all the time, at least two or three times a month. This is the first time I have seen Orcas while from the a ferry. It got everyone out on deck.

Olympic Rain Shadow

I spent the day on the northwest portion of the Olympic Peninsula. Had a bit of dread given the storm off the coast and it was dumping all the way till I got to the Hood Canal Bridge. Then a peak of blue sky and no rain. I ate my lunch sitting in the sun! A great Olympic Mountains rain shadow experience.

Telford Scabland, Highway 2 between Creston and Davenport

Telford Scabland, a tough place for driving fence posts.

Large tracts of Washington’s landscape were shaped by the Missoula Floods. One prominent feature found along the flood route is scabland topography. Scablands are areas where all of the soil was stripped from the bedrock and the bedrock was ripped up leaving a scabland landscape. With most of the bedrock consisting of dark basalt lava rock the term scabland is very apt.

The Telford scabland is crossed by US Highway 2 between Creston and Davenport west of Spokane. It is easy to be locked into driving the straight stretches of highway heading east towards Spokane or west from Spokane and not fully appreciate this landscape unless you’re versed in the Missoula Floods. The surge of water from the rapidly draining Lake Missoula flowed into Washington State and Glacial Lake Columbia. Glacial Lake Columbia overflowed at multiple locations including a broad swath north of the Telford scabland.

Missoula Flood way paths

Telford Scabland

The scabland is mostly brown with rectangular fields on

the elevated areas where the flood waters did not pass.

Note the large number of lakes within the scabland area.

Not all of the local bedrock is basalt. If you are alert or not driving in the dark, you might notice an outcrop of much older granitic rocks east of the town of Creston. These rocks are part of the Lincoln Metamorphic Core Complex, one of a series of metamorphic core complexes that are located across the northern tier of Washington State. A little side trip to take in the view from Creston Butte a mile south of Creston is to take a trip back into deep geology time as the butte is underlain by possible Precambrian quartzite. The Columbia River Basalts are thinner here and the much older rocks that dominate the metamorphic complexes of the Okanogan Highlands and mountains north of the Columbia River crop out on through the basalt in a few places on this high plateau.

Though rocky scabland, this area is not a desert. The area is full of lakes and in areas where soils are thicker there are stands of ponderosa pine and thickets of brush. The ponderosa pine forest can be seen along stretches of Highway 2 and occasionally a small lake can be glimpsed from the highway. The elevation of the area traversed by Highway 2 is just below 2,500 feet hence the somewhat wetter conditions. The Telford scabland becomes drier to the southwest as elevation lessens.

Scub steppe scabland with ponderosa forest

Kolk or pothole pond in scabland

Although not pristine, the area has been used for grazing for many years, this part of Washington is a big area of wild land. Significant blocks of this area are within public ownership. Bureau of Land Management (BLM) owns an approximately 30 square miles of contiguous land southwest of Highway 2. I believe this may be the largest contiguous BLM block land in Washington State. The BLM owns an additional approximately 8 square miles adjacent to Highway 2 and approximately 20 square miles west and northwest of Odessa. In addition the 21,000-acre Swanson Lakes Wildlife Area managed by Washington State Fish and Wildlife abuts the BLM land. The area also contains roughly 18 square miles of Federally granted trust lands granted to Washington State in 1889 some of which abut the Swanson Lakes Wildlife Area and the BLM land.

The Swanson Lakes Wildlife Area is the result of wildlife mitigation by the Bonneville Power Administration for Lake Roosevelt wildlife loss due to Grande Coulee Dam. The lands were acquired in the mid 1990s. Washington Fish and Wildlife has been introducing both Columbia sharp tailed grouse and sage grouse to the wildlife area. These birds had been extirpated from the area by the late 1980s.

Despite the term scabland, this is land has great fishing, hunting and just solitude with wide views. I spent a nearly full moon night on the BLM land a few miles south of the highway last summer. Woke in the early light to coyotes calling out to each other, brewed a pot of coffee and headed to Spokane feeling very refreshed.

The scabland area is surrounded by soft rolling hills of eolian silt covered with wheat fields on the high ground untouched by the great floods. A few peaks rising above the wind deposited sediment are ancient rocks of the metamorphic core complexes and Precambrian rocks of the ancient continental margin.

Wheat on eolian silts with buttes of Precambrian rocks in the distance