Debris Flows, Logging and Marbled Murrlets - Lake Cavanaugh

Lake Cavanaugh is located within the northwest Cascades near the southern Edge of Skagit County. The 2.75 mile long lake was formed by continental glacial ice that flowed eastward from the northern portions of the Puget ice lobe into the North Cascades. 

Lidar bare earth imagery of Lake Cavanaugh area

Blues arrows indicate ice flow direction with the arrow on the left being the main flow path of the Puget ice lobe and the blue arrow across the top indicating the ice flow from the Puget lobe up into the North Cascades. 

Lake Cavanaugh may have been an area of weaker fractured rock as it is aligned with the Darrington-Devils Mountain Fault zone.   

The south shore area of the lake consists or a series of alluvial fans associated with steep creek drainages coming off the north side of Frailey Mountain. Frailey Mountain is a steep ridge that rises about 2,000 feet above the lake. The bedrock on the mountain is mostly metamorphosed ocean floor basalts of the Eastern Melange Belt, a tectonic terrain. Sandstone and conglomerate of the Oligocene age Bolson Creek Formation underlies some of the mountain as well and there are areas of glacial sediment on the lower slopes.

Due to the steep slopes and narrow drainages the small creeks on Frailey Mounatin are subject to periodic debris flows.

Debris flow on one of the unnamed creeks in 2016.

There are some policy issues associated with these creeks but that will be another post. 

Lake Cavanaugh area was heavy logged in the past.  Bob and I came across this stump while heading up the slope to assess a potential debris flow source area.

The 1941 aerial image looks a lot like a lidar bare earth image. The clear cut logging throughout the area was very intense.   

  

1941

Note that there was a stand of trees left on some of the steeper upper slopes (but not the ridge line) in the 1941aerial. As the forest grew back the old trees are still evident in 1974 aerial. 

1974

They are not as apparent in the 2017 aerial, but logging in the area has started up again as the second growth is now merchantable and logging in the area has been intensive over the past 10 to 15 years. 

2017 - old tree stand circled in red

But the old trees remain. This remnant stand of old trees provides nesting habitat for marbled murrelet, an endangered sea bird that nests within old forest stands. A buffer around this habitat area is required for forest practices (proposed harvest). An added benefit is that bird's nesting presence and protection also reduces the potential for the very steep slopes from being damaged by tree harvest and has limited some of the recent proposed harvest on the north slope of Frailey Mountain.   

Cascade River Valley and Remembering Scott

I had a venture up the Cascade River in the North Cascades. The Cascade River is a tributary river to the Skagit River. The river was flowing hard through a bedrock section of the canyon from the parade of mild temperature storms that have passed through over the last week, but given the high altitude of much of the watershed it was not at flood levels. 

During my traverse I came across this boulder that had recently landed in a patch of sword fern and had a fresh chip on the surface of the rock.

Looking up the slope did not reveal much as to the source of the rock.

However, this area of the Cascade River is in a deep valley with steep valley walls rising 4,000 feet from the the river. My guess is the rock derived from a band of steep exposed boulder rich glacial sediments about 600 feet up the slope.

All in all I got very wet ploughing through ferns and brush in a forest of western hemlock, western red cedar and Douglas fir.

Heading out I was struck by the splash of yellow gold of a cottonwood amongst the evergreens.

The splash of color reminded me of a past fall trip up the Cascade River valley after a good summer of field work in and above the Cascade River valley.  I vividly remember the fall colors of that trip and always associate that trip with sadness and loss but also some joy. The brightness of those remembered colors as well as the bright cottonwood tree I saw on this day remind me of the brightness of Scott. I always associate him with the Cascade River valley in the fall even though he never saw it.

Mount Baker Steam before the Rain

 Before the latest weather front moved in I had a short notice/time critical job on Orcas Island. This time of year I can push back departure to the 7:30 AM boat instead of the 5:30 AM boat since it is still dark when the 5:30 boat arrives on Orcas. The ferry schedule has been tweaked a bit due to recent staff shortages related to COVID. 

Waiting at the dock I had a nice view of the early light and Mount Baker. With frosty temperatures and moist air a pretty good steam plume was emitting from Sherman Crater on the south side of the mountain. 

Mount Baker with Twin Sisters Range on the right

      

Pine Creek Loses some of its Forest

 

Malden Post Office before the fire

Attribution of a single wildfire event to global warming is confounded by lots of other factors. The Malden area and Pine Creek valley are located in a climate edge area where pine forests meet grass lands (and now dry land wheat fields) in a mosaic landscape. Pine Valley where Malden is located was already in a fire prone area. Every summer the area becomes dry enough to burn with the grasses and brush being susceptible for a longer period and the trees for a shorter period. Towards the southwest that length of time becomes longer and to the north and east the length of time is shorter. Pine Valley is in a boundary area just moist enough that tree killing fires have been infrequent enough such that the valley has significant forest stands. 

With warmer average temperatures the length of time the area is susceptible to fire is now longer. But other factors can increase fire risk - years of fire suppression and changes to land use also alter the fire risk and how a fire will behave. With lots of roads, fires in Pine Valley could be readily suppressed and put out as long as fire weather conditions were not severe. Land use changes also play a role. Over time the forested areas began to encroach into the Malden town site.

The weather event associated with this fire included very high winds associated with an Arctic cold front that surged across the area from the northeast. The high winds had followed several days of at or near record daily highs in the region. The weather set up and fire risk was predicted several days before it took place (Inland Northwest Weather.blogspot). The same weather event was also associated with a much large fire that burned over 60 miles in the Okanogan Valley as well as the very intense wildfires on the west slopes of the Oregon Cascades.   

Pre and post fire aerial images show that a fair bit of the forests that were in the Pine Creek valley burned during the fire. 

Malden 1954

Malden 2017

Malden 2021

Northeast of Malden 2017

Northeast of Malden 2021

Pine City 2017

Pine City 2021

Malden, Washington Notes: Ice Age Flood Route

A bit over a year ago a wildfire burned much of Malden, Washington. Due to the extent of the destruction, the already tenuous economy of the small town and the very delayed National Major Disaster Declaration by the President, there have been follow up stories and takes on the fire and the aftermath (https://www.seattletimes.com/seattle-news/the-day-a-wildfire-took-malden/). Northwest Public Radio and Spokesman Review as well as Spokane area TV stations have continued to report on the town's effort at recovery.  

Malden Post Office before the fire

Malden is a bit off the usual routes; hence, I thought a little background on the landscape of Malden and the vicinity would be of use. I passed through Malden about a month before the fire and also on a trip to Rock Creek and Bonnie Lake (bonnie-lake-precambrian-schist). On that earlier trip I paused at the Post office (above picture). 

Malden is located in Pine Creek valley in the norther part of the Palouse. J Harlen Bretz (1923) recognized that the Pine Creek valley was a pre existing valley that was further eroded by ice age floods, "The valley during this episode in its history was but a channel. The glacial stream filled it from side to side for a depth of tens of feet. This is shown a few miles above Malden, where the stream flooded over a low shoulder of basalt, cutting a channel in the rock at least 40 feet deep, though the main valley alongside was a wide open and received gravel deposits." 

Map of Spokane Flood routes from Bretz (1925)

Flood water spillway from upper Latah Creek into the North Fork of Pine Creek (Bretz, 1923)

The ice age floods that Bretz was describing were the result of water spilling over from Latah Creek. The Okanogan ice lobe dammed the Columbia River forming glacial Lake Columbia in the backed up the Columbia River. The lake extended up the Spokane River and Latah Creek, a tributary stream to the Spokane River. When the ice dam at that formed ice age Lake Missoula collapsed, the flood waters surged out of the rapidly draining lake and into the Spokane area and into Lake Columbia. The sudden influx of a massive surge of water resulted in Lake Columbia overtopping at numerous low divides to the south. One big spill way is the Cheney-Palouse scabland tract southwest of Spokane. Interstate 90 passes through part of the tract. But some water backed up Latah Creek and spilled over a divide into the Pine Creek Valley.  

DEM of spillway from Latah Creek into Pine Creek

The ice age flood features in Pine Creek are a bit more subtle than the raw wide stripping of soil that took place in the very broad Cheney-Palouse route. But the features were noticeable to Bretz and are not consistent with the other valleys that were not flood routes that pass through the Palouse landscape. 

Another factor that softens the flood features in the Pine Creek Valley is that this flood route has a bit wetter climate than those to the west and the valley has more areas of pine -- hence the name Pine Creek. More on that on a future post.    
   

Pyrite in the Gravel

One of the sources of crushed gravel in Skagit County is a rock quarry. The quarry has mined large blocks of rock for levy projects, but the process of breaking the large intact blocks of rocks creates smaller rock. Hence a side product is angular crushed rock gravel for driveways and parking areas. The angular rock along with the fines within the crushed material forms a hard drive and parking surface. 

Crushed rock gravel parking area

Walking across one of these driveway areas on a moonlit night I noted remarkably bright spots in the gravel. My geology brain clicked in and I recalled the likely source of the gravel being a rock quarry excavated into some altered ocean floor igneous gabbro. The ocean floor rocks are a Jurassic age accreted terrain slab of ocean floor. Hot fluids flowing through and old ocean floor precipitated minerals. The bright spots I was seeing in the gravel was moonlight reflecting off of the very smooth surfaces of cubic pyrite minerals.       

A larger pyrite mineral - most are much smaller

I spotted this during the day when a very bright reflection struck my eye 

Pyrite is an iron sulfide mineral and is pretty common secondary mineral. Its breakdown via weathering in pyrite rich crushed mining tailings is a source of acid mine drainage. Its presence in some limestone deposits or the rock aggregates mixed into concrete is detrimental as the pyrite breaks down the sulfur released will form acids that will damage wiring, pipes or other metal in the concrete and can also form hydrogen sulfide foul odors.  

 

Ground Wasp Hazard Season

Field work hazards vary depending on where one is working and the time of year. In September in western Washington as well as elsewhere a hazard that I try to be alert for is ground wasp nests. 

Yellowjacket nest

The life cycle of the wasps is such that the nests become very large in late summer and the nest becomes populated with adult wasps that will readily defend the nest. Fortunately the wasps rarely sting when passing near the nest, but accidently stepping into or on a nest in late summer is a hazard.

I managed to avoid stepping into any nests last summer and thus far have a avoided doing so this late summer. Last week a client helpfully alerted me to a nest along a survey path cut through the brush prior to my field venture. I noted the small fast flying wasps near the nest shown above before spotting the entrance. 

My last encounter with stepping into a nest was on a very steep slope. The usual fast escape via running was impeded by the slope conditions which meant I had to crawl up the steep slope as fast as I could and likely further disturbed the nest as I began my escape. Once I reached the top of the slope, I was able to run, but continued to be stung. The next step was to shed my shirt and pants as fast as I could. Wasps release odors when they sting which stimulates additional stings and additional wasps to attack. My car was not far away and I had extra clothes (a typical habit as I often get wet doing field work). Even a half hour after my encounter there were still wasps stinging my dropped shirt.