My contribution to the columnar state of mind

Dave Tucker alerted me to a request for columnar jointing from Washington State from magmacumlaude.blogspot . Apparently a number of geos are posting about columnar jointing. As any magmatitist, tuff cookie knows, Washington State has lots of columnar jointing because we have have lots of thick lava flows. The Columbia Basalt Group is one of the largest lava fields in the world and we also have the Cresent Basalts on the Olympic Peninsula and some more basalts in southwest Washington. And of course we have the Cascade volcanoes.

David Tucker obliged with a series of his pics HERE. Other geo blogs with columnar posts are
geotripper.blogspot
geologyblues.blogspot
geologyblues.blogspot (Phillip did two)
outsidetheinterzone.blogspot
highway8a.blogspot
highway8a.blogspot (Silver Fox did two)
glacialtill.wordpress
and perhaps the best entequilaesverdad.blogspot

So my contributions to the cause:

Cliffs of the Palouse River Canyon - Columbia River Basalt Group 

Devils Canyon

Wanapum basalt is on the left with younger basalt of the Saddle Mountain basalts filling in the ancient canyon and then topped by a third flow.

Twin Rocks, south of Wallula

Horse Heaven Hills at Wallula Gap

And from the tribal homeland: "I went to the huts of some of the savages that were there, who told me of the great misfortunes of our people who were drowned at that place and showed me many jewels and valuables of theirs, which distressed me greatly" - Fancisco Cuellar, describing the northern Ireland coast in 1589.

Esker Near Lake Padden?

Another UPDATE: See below
UPDATE: See below
I paid a visit to my local County Council last night regarding Lake Padden, a lovely gem of a lake in south Bellingham. Essentially every time anything comes up regarding that lake either the City Council or County Council gets to see me. Beforehand I was checking out the watershed boundaries using LIDAR imagery when besides the really cool folding apparent within the Chuckanut Formation, I spotted an interesting feature snaking across the slope to the northeast of Lake Padden. I have not ground truthed this feature, but it sure looks like it is an esker.

Possible esker near Lake Padden

The esker is the squiggly line across the otherwise smooth slope.

Clicking on the image will make it a lot easier to see.

Eskers are formed by water flowing underneath glacial ice, but instead of eroding downward into the ground surface, the water erodes upward into the ice. When the glacial ice melts away an inverted stream bed is left behind. LIDAR is pretty good at spotting eskers. They are otherwise hard to see in western Washington where the land is covered with trees.

Eskers are part of the National Natural Landmark designation on the Waterville Plateau in central Washington. The Waterville Plateau is west of the Grand Coulee. The continental glacial ice margin was located across this plateau and wonderful eratics and terminal moraine features as well as eskers cover the area north of Highway 2. The following Google earth Images are of a esker near Simms Corner.

Esker on the Waterville Plateau

Oblique view of esker showing inverted stream bed.

Update: Dave Tucker emailed that he knows of one geologist that did check out the possible esker. He thought it might be a morainal feature. I'll throw out another theory I have that the feature appears to be just below the crest of the slope from the north and may be a small depositional feature as the glacial ice rode over the crest of the slope from north to south. Anyway I look forward to hearing from some ground truth views of the feature. I do know that there is a morainal like feature to the southwest of the word Padden on the above map. As always thanks Dave for the info.

Another Update: Doug Clarke (personel communication, 2010) interprets the feture as morainal. Thanks Doug.

Two thoughts on this. One is the intent of this blog is to share observations so the input is greatly appreciated. And two, it is clear that LIDAR helps identify features that can be pursued in the field. Now I am thinking about what type of moraine and why is it there. But keep in mind that not all questions and features are readily answered or explained. Think Mima Mounds or just exactly what happened to the pronghorn antelopes in eastern Washington.

Fog on the Horse Heaven Hills south of Benton City

Last week I posted a bit on having a sunset picnic on the hinge of the Horse Heaven anticline just south of Benton City. I have a different view of the same location from late last fall.

Fog on the crest of the Horse Heaven anticline south of Benton City

The fog bank covered the ridge line for well over 24 hours. Having lived within view of the Horse Heaven Hills, I know that this is not an unusual scene. During the winter air flow from the southwest out of the Columbia Rover Gorge rises up the south slope of Horse Heaven anticline and cools enough to begin condensing. Then as it descends the north slope of the anticline it warms and evaporates before reaching the valley floor.

McBee Road can be seen angling up the slope in the right portion of the picture. The lumpy area on the lower part of McBee Road is an old landslide deposit from the slope above. Lots of slides in this area are associated with the Missoula Flood; however, this particular slide came off a slope well above the flood elevation. The bedrock on the crest of the anticline is highly fractured and the slope is steep.

The topo map of the area shows how the crest of the anticline is hinged at this location and changes from a northeast trending fold to a southeast trending fold near where McBee Road crests the ridge line.

The slopes of the ridge at this location are predominantly bunch grass. The land in this area is managed by the Bureau of Land Management (BLM). Relative to Oregon, Idaho and other western states, Washington State does not have as many large tracts of BLM land. As evidence in the picture below the grass land is in good condition, but I do not know the details of the BLM management plan for this area. There currently is a weather tower on the summit ridge likely doing a wind study so windmills may be in the future on the ridge line of this BLM land.

Bunch grass on the slopes below McBee Road

We made the drive up the ridge last fall into the fog. The temperature in the valley was mild - upper 50s. The ridge line was just at freezing with just the beginning of ice rime formation. When I lived in this area, my mates and I ran these ridge lines in the winter and often ran through ice fog like that seen above. We would be completely covered with frost except our skin.

    

What Are They Looking At? Another nice sail on the Steilacoom II and a Natural Bridge

 I took two pictures of these folks enjoying the back deck of the Steilacoom II to capture the rock of the boat. Note the difference in the horizon between the two pictures. The Port Townsend to Keystone run crosses the entrance to Admiralty Inlet between Puget Sound and the Strait of Juan de Fuca. As such there are occasions when there is a bit of ocean swell. The ride is not long enough to get sea sick on. At least I have never seen anyone get sick, but I was on the boat once when a wave broke through the car deck.

Anyway as last evening's crossing progressed the sunset got better and better and brought lots of folks out onto the deck.

Point Wilson at sunset with the Strait of Juan de Fuca to right

Most of yesterday's ventures were simple hazard assessments, but one site had an odd feature that is a first for me. A small slope failure leaving a natural bridge.

Pile Driving Noise Changes

Last winter I had a small project making sure some piles were embedded deeply enough for a dock and landing at a small inlet off of Hood Canal on the east side of the Olympic Peninsula. (Hood Canal is named a canal but is a natural body of water formed during the last glacial period). I was not involved in the initial design or scoping of this project, but a clever engineer placed a note on the design drawings that the pile depth should be approved at the time of pile driving - passing responsibility to whoever took on the oversite.
One of the permit conditions was that the piles were to be driven using a vibratory pile driver.

Driving a steel pile with a vibratory driver using a crane on a barge

This permit condition is the result of studies on water noise impacts to fish and sea mammals. The more typical hammer pile driving can generate intense noise pulses in the water that are intense enough to tear fish bladders and destroy the hearing of fish (Laughlin WSDOT, 2005 and 2010). Lots of piles are driven into water for docks and bridges. Hence, this issue is posing a challenge for in water works - think ferry docks, bridges, and marinas. Washington State Department of Transportation has studies using bubble curtains around piles to dampen noise with some success, but as always "more study" is needed. Lots of physics, biology and acoustics; reading the studies is a good brain work out and certainly a regulatory challenge.

Studies on hammer driving which is basically dropping a big weight on top of the pile to drive the pile versus vibratory driving indicate that the sound intensity and pulses are substantially lower for vibratory pile driving. Hence, the condition my client had on pile driving. The vibratory pile driving basically shakes the pile through the sediment. I was surprised how well it worked, but we were unable to drive through the old log road that had been constructed along the shoreline without moving the pile locations slightly.

Steel piles prior to dock and landing reconstruction. The two sheds are 100+ year old structures from old fishing days. Grassy area at the base of the slope was an old road bed as tide lands were the first "highways". 

A little more on Shoalwater

As a follow up on yesterday's post on Cape Shoalwater I marked the location of the rock armored home that was pictured in yesterday's post on the 1990, 2005 and 2006 aerials/satellite images. The change from 2005 to 2006 is ---- use your own adjective.

House site 1990 is circled

2005 and the water view is fantastic

2006 and the ocean can be viewed from three sides.

I am not sure of the permitting rules in Pacific County, but it appears the home was built sometime after 1990 as I can't see it or an access drive to the site in the 1990 image. There are allowances for reasonable use of your land that varies from community to community. In a small coastal county like Pacific County living with the fact that much of the developed area will be inundated by tsunami waves when the next big subduction quake takes places, the attitude towards the impermanence of homes on sandy shores may not be the same as more stable areas. I have to say I was impressed with the effort by the property owner to save the house without moving it. Keep in mind this is the open Pacific Ocean and this coast gets really big waves. Dave Tucker noted via email that the home was posted with a sign saying Isle Knot Go. Another home was labeled Willy B Next.

One last note. As stated in yesterday's post most of the shoreline in this area is accreting with lines of dune sets paralleling the coast. As the new land and sand is added, the dunes are covered with forest. The low areas behind the dunes are wet land areas ideal for growing cranberries. The farm fields in the upper right of the satellite images are cranberry bogs.

Cranberry bog in winter near Cape Shoalwater



Cape Shoalwater or Washaway Beach

Cape Shoalwater is located at the north entrance of Willapa Bay on the southwest coast of Washington. This is a site of very rapid coastal erosion. I found by comparing satellite images from 1990 to 2009 the rate of erosion is impressive. Since the late 1800s the erosion has moved inland over 2 miles. Prior to 1990, thirty homes have been destroyed or moved, a light house, school, cannery and grange halls have been lost and the state highway and a cemetery were moved. In 1995 the State Department of Transportation spent 27 million dollars building a heavy groin and jetty to protect the new highway. 

Red line marks the 1990 coastline

2009 coastline with 1990 coast marked in red

I got a bit confused when I was at the site as I was looking for a sand dune with buried trees. It turns out that nearly the entire dune is now gone. I took a few pictures of the old state highway and erosion features. It is thought that the erosion is caused by a natural channel realignment at the entrance to Willapa Bay from the south to the north and it appears that the erosion may have slowed in the past few years. The erosion is the opposite of the general accretion that is taking place on other areas of the southwest Washington coast.   

The old highway comes to an abrupt end

Fragments of road on beach

View of heavily rocked home site from top of the last part of an eroding dune.

Looking north from eroding dune

Erosion towards homes

North Cascades and Grizzly Bears

Grizzly bears in the North Cascades were in the news this week as the Forest Service has begun a field project looking for grizzly bears in Washington State's North Cascades Press Release Here. The quest for grizzly data in the North Cascades has been going on for a long time in part because Washington's North Cascades has been identified as a Grizzly Bear Recovery area. Grizzly bears are present in northeastern Washington in the Selkirk Range, and grizzly bears are present in the North Cascades and high interior plateaus of southern British Columbia adjacent to Washington's North Cascades. A few years ago the British Columbia government was importing grizzly bears into the Manning Park area to augment the population north of the border. The estimate by the bear folks I have spoken with are that there are perhaps 20 grizzly bears in the North Cascades.

During the summers of 1989 through 1991 I did extensive field work in the North Cascades that involved back backing deep into the wilderness. At that time there was a bit of a buzz about the possibility of grizzly bears in the North Cascades in Washington State as a number of unconfirmed grizzly sitings had been made. I was doing some work in the Park Creek Pass area and met a group of hikers very excited about a grizzly in the meadows just south of the pass. I headed up there from my camp in hopes of seeing the bear and because I had to do some rock collecting and mapping in the area west of the pass. I did see a very big bear. I watched it for awhile and then decided I really need to get past it in order to do my geology work. I let out a yell figuring the bear would move on and I could get by. The bear did not even look up. It was very focused on eating blue berries. There was not a lot of space to pass the bear, but I decided it was keener on the berries and I was of no interest so I proceeded to walk by it coming within about 30 feet. It was most definitely a black bear, but it was huge and I estimated it at 450 pounds. I was very uncomfortable being that close and found a much more distant route back to camp. Before dark a helicopter flew into the pass area and I later confirmed that the bear was identified as a black bear.
My other big bear encounter was about two miles past Monogram Lake along the divide between Marble Creek and Newhalem Creek. I was aware of bears being in that area and had set up my camp on a rather uncomfortable rock ledge immediately adjacent to a small glacier. It was a cold camp site, but surrounded by ice and rock for one quarter mile and I did not want to loose my camp to a bear raid like a geologist that had been in the same area a couple of years before. Sure enough my mapping partner and I saw lots of bears. We spent the better part of a day debating about whether one group were grizzly bears. They looked like grizzly bears, but it was my opinion that they were too small. To this day I am still unsure and I do not know if the Forest Service study will include the Marble Creek - Newhalem Creek divide.
The Monogram Lake and the high ridge behind it along the divide are ideal bear habitat and there are still plenty of bears up there. My son went up to the lake this summer and saw at least 7 bears and saw bears during the day "all the time".
Few people go much beyond the lake. When I was mapping up there I spent 12 days up there and never saw anyone. I also took two trips up into the Newhalem Creek valley and never saw anyone there either. While the area is isolated today, it was not always as islotated. A road used to go about five miles up into Newhalem Creek to within two and half miles of the ridge line and much of the Newhalem Creek watershed was logged in the 1950s. A marble mine was formerly located at the base of the ridge in Marble Creek. During my time on the Newhalem - Marble Creek divide, I found rifle shell casings indicating that the area was formerly used for hunting.
The area is now within the North Cascades National Park and is managed as wilderness and the bears are thriving. Whether or not there are grizzly bears above Monogram Lake, there is outstanding habitat and other areas of grizzly bear habitat exist throughout the North Cascades. But even if here are a few grizzlies left, the population is likely too small and will require active efforts including introduction of bears to stabilize the population. There have been approximately 40 "class 1" sitings over the past three decades and a mid 1990s study using hair snags similar to the new study provided DNA confirmation of one bear. The Grizzly Bear Outreach Program (GBOP) has received funding from Washington Fish and Wildlife and the Forest Service as well as private donors to help build understanding of grizzly bears as well as black bears so that if and when a recovery project starts people living near the recovery area will have a good understanding of the bears living near by even if they never see them.     
   

Picnic at the Hinge in the Horse Heaven Hills Anticline

Casting Long Shadows at the Crest of the Horse Heaven Anticline south of Benton City

Earlier this month after a hard day of work in eastern Washington (not really) Lisa and I headed up for a sunset picnic on the hinge of the Horse Heaven Hills anticline. The Horse Heaven Hills are one range of hills and bluffs that is part of the Yakima fold belt. The Yakima fold belt consists of a series of generally east-west trending anticlines and synclines that fold the landscape of south central Washington. The anticlines have relatively gentle south slopes and very steep north slopes with broken rocks and faulting. The folding has been going on a long time with north south compression dating back to and during the eruptions of the Columbia River Basalts 17 million years ago (Reidel, Campbell, Fecht and Lindsey, 1994).
The folding has created landscapes that are being modified today. The elevation changes create micro climates and changes in soil types that have defined grape viticulture areas as well as funnelling wind that is now being developed as wind farms. Another attraction of the anticlinal ridges is the relatively natural setting they have preserved. Most of the scrub-steppe habitat of eastern Washington has been supplanted by farming and towns, but the ridges have remained un tilled and although perhaps over grazed in the past are the areas where the scrub-steppe has remained somewhat in tact.
For our sunset picnic we headed up McBee Road to just east of Chandler Butte. We walked the ridge line to a summit area. What the pictures do not capture is the fact there was a major ant hatch with swarms of winged ants drifting along the ridge line. At times I felt like the grill of a car covered with sticky ants and ant wings. But as the light faded and a very slight breeze started, we were able to enjoy our food and the sunset over the Yakima Valley with views of Red Mountain, Rattlesnake Mountain as well as the big strato volcanoes of Rainier and Adams.
The spot we chose is at a hinge in the fold. The Yakima folds trend east northeast until bending to the east southeast. This bend happens to coincide with the Olympic-Wallowa Lineament, a feature that drives all sorts of geo speculation and head scratching. Our picnic spot on the northern most portion of the Horse Heaven fold provided a great view of southern Washington. I have a fond memory of this spot as it was the location where I went to see the total solar eclipse in 1979.

Sam enjoys a back stracth above the Yakima Valley

View to the west with Mt Adams and Rainier on the horizon



A Foggy Day in Port Townsend and on the Steilacoom II

Port Townsend from the Steilacoom II

Yesterday's work involved a fairly long meeting that ended with me taking a little geology field trip along the Port Townsend shoreline below Morgan Hill. The morning fog had turned to rain by the time I began my walk. Summer really does appear to have ended as I had my first good soaking in a while. Ended the field work with a hot bowl of soup and a Guinness at a bar on Water Street.

Bright sunny days may be a rare thing for a while, but the ride on the ferry provided nice views anyway. For the past couple of years the Keystone-Port Townsend ferry run has been served by the Steilacoom II. The previous Washington State ferry boat had been pulled from service due to cracks in the hull. The Steilacoom II a boat owned by Pierce County for its ferry service between Steilacoom and Anderson Island has been filling in. The new Washington ferry boat is undergoing test runs in Elliot Bay and is supposed start its Port Townsend service in about a month. The ferry ride passes through what was formerly a triangle of fire with forts at Fort Worden north of Port Townsend as seen above and from Fort Flagler on the north end of Marrowstone Island and Fort Casey on Whidbey Island. 

North end of Marrowstone

West Coast of Whidbey Island at Fort Casey

My geology field work site at Port Townsend's Morgan Hill Bluff

Glacier Peak Debris Flows

The Washington Casade Range has five strato volcanoes: Mount Saint Helens, Mount Adams, Mount Rainier, Glacier Peak and Mount Baker. Mount Rainier has been described as the most dangerous volcano in the United States due to the fact that significant population centers have been built on areas underlain by mud flows from the volcano. Mount Saint Helens is of course well known having erupted 30 years ago. Mount Adams is not so well known in western Washington, but is a significant icon above the Yakima Valley and south central Washington. Mount Baker provides a scenic back drop for the lower Skagit Valley and San Juan Islands and is very apparent even from Seattle.
I often think of Glacier Peak as being the sneakiest at it lies tucked back into the core of the North Cascade Range where its summit and flanks blend in with the high peaks around it. Hence, it is easily the least known of Washington's five strato volcanoes. Although not well known, it has been an active volcano with at least three major mud flows since the end of the last glacial period 13,000 years ago and Glacier Peak dacite fragments show up in preglacial period sediments throughout Puget Sound. A major mud flow from Glacier Peak would have a significant impact to residents in Skagit Valley and might create some transportation challenges for people like me in the Bellingham area wanting to head south.

I have encountered the soils derived from the mud flow colored orange on the map above. The deposit is just beneath the surface in areas east of Sedro Wooley along Highway 20 and is reflected in extensive wetlands in that area. Poorly drained soils west of the Mount Vernon area are also underlain by Glacier Peak mud flows. 

***UPDATE**** 

Based on a comment by Dave Tucker via email and posted below, the above map perhaps overstates the travel distance of mud flows from Glacier Peak. Based on his observations and others the orange area on the map may in part be the result of reworked Glacier Peak material transported down valley. Not an unreasonable suggestion as I would assume a bunch of mud and ash up valley would then be transported down valley. And based on that, the catastrophic risk may be substantially less. 

Fog at Ebey's Prairie, Whidbey Island

Had a nice field day yesterday exploring filled tide lands in Anacortes, a forested site on a shoreline on the east side of Whidbey Island and another site on central Whidbey Island. I got the view above of fog moving through a stand of forest near Ebey's Prairie south of Coupeville. The site is part of Ebey's Landing National Historic Reserve http://www.nps.gov/ebla/. The Reserve also has a nice blog HERE. The Reserve is a means of preserving a landscape that is unique to western Washington. I feel fortunate that I get to work and pass through this area as part of my job. The building in the photo is the Ferry House. The Ferry House even has its own Face Book page HERE.     

Boorish Tomato Gardeners of Western Washington

Last night's harvest

Western Washington gardeners can be a bit boorish about their tomatoes. This is particularly true in Bellingham where temperatures rarely reach even 80 degrees in the summer. This summer was very cool so western Washington tomato gardeners are bitter about ocean temperatures in the tropics messing up our heat units. That said, I have been harvesting gotten tomatoes. Boorish or not I am proud of it!
My tomatoes are planted at the top of a rock retaining wall that faces south and west so the heat is maximized. Northwest Washington is a bit short on heat units compared to central and southeast Washington. I hope to get more tomatoes and found as long as there is not a hard freeze I can pick tomatoes through to the end of October. Last evening I covered the plants with a tarp. While this might provide some additional warmth, the main thing is to keep the rain off of the plants otherwise the fruit splits and a black fungus will kill them. In early October, I pull the entire plant out of the ground and hang them under the eaves. A couple of years ago, Lisa was working out of town so I hung the plants in her studio and picked tomatoes all the way to Thanksgiving. It worked great but that won't be happening again.
An alternative to all the work and tending of plants is to live elsewhere or take a trip to the east side of the State. A stop at the Pasco Farmers Market will provide lots of heat unit rich produce and we try to make it there every year.

Marrowstone Island Geology Trip to see Nodules (actually concretions) and Lips

I previously did a post on Indian Island in Jefferson County. Marrowstone Island is another Jefferson County island immediately to the east. Marrowstone is accessed via Highway 116 which crosses the south end of Indian Island and crosses no more than a culvert onto Marrowstone Island.

Crossing to Marrowstone Island

Fort Flagler State Park is located on the north end of the island at the old fort and includes old army houses with spectacular views that can be rented. This fort is one of several that were built to prevent a naval invasion of Puget Sound. Any navy be it Spanish or Japanese would have faced a gauntlet of hardened rifled cannons if they tried to enter Puget Sound. Another day use state park is located at the lovely Mytsery Bay on the islands west shore and the State Parks owns a large undeveloped parcel on the southern tip of the island.
Marrowstone is mostly rural large lots with a few pasture farms. Up until a few years ago a common site on the island were signs in favor and signs opposing public water on the island. Being an island in an area with relatively low rain fall combined with unfavorable geologic conditions water availability has limited development on the island such that properties that would otherwise have homes did not because there simply was not adequate water. A couple of years ago public water was extended onto the island so additional homes will be built and existing homes that had water problems again have potable water. The area is still rural and zoning on the island is such that for the most part there will not be huge changes in the short term. I did note recently that the assessed value of a large property on one area of the island had increased dramatically after water became available.
The east side of the island provides a great year round geologic outing for those that find themselves in this part of Washington State. Drive north along the west shore of the island past the hamlet of Norland on Mystery Bay and turn right onto Beach Drive. Follow this road straight across the island to Jefferson County's East Beach Park. From there hike down the beach to the south along the east side of the island to Nodule Point. The hike is from Beach Park to Nodule Point and back is approximately three miles with no hills as it is entirely on the beach.

The first part of the hike provides great exposures of advance glacial outwash capped with glacial drift. The advance outwash consists mostly of sand that was deposited by glacial outwash streams as the glacial ice advanced southward into what is now Puget Sound approximately 20,000 years ago. The glacial drift was deposited directly by the glacial ice as the glacial ice covered the area. The drift consists of an unsorted mix of sand, gravel and silt with an occasional boulder along this reach of shoreline. Because the sediment is derived directly from the ice, the grains have not been sorted by flowing water in sharp contrast to the well sorted underlying sands with a few thin silt layers in the outwash beneath the drift.

Glacial drift over advance outwash

Close up of unsorted glacial drift.

Beside the very good exposures of drift and outwash, this bluff provides excellent examples of shoreline bluff erosion. The first few times I had been on this shoreline most of the sloping lower bluff slopes were grass-overed with a few small Douglas fir trees. Four winters ago a large low pressure system combined with a very high tide and high winds caused extensive erosion along this reach of shoreline. A similar event took place this last winter as well. The erosion caused most of the lower portions of the bluff to become over steep and led to sloughing of the loose sand. This further undermined the very hard compact drift which holds vertical cliff faces and subsequently slabs of drift have calved off of the upper slope onto the slopes and beach below. Various stages of bluff recession can be seen all along the bluff for the first mile of this beach walk.

Recent slab of drift collapsed with a few feet of lost upland property.

One interesting site is a spot where the glacial drift is particularly thick. A chain link fence can be seen from the beach below looking up at the top of the slope. behind this fence is a cemetery. An interesting future problem with a bluff recession I have estimated at 2 inches per year.

Cemetery is just behind fence. Note the sheet of roots exposed after a slab of glacial drift broke away.

A little past the cemetery the outwash unit pinches out and the glacial drift becomes bouldery and a little further on bedrock crops out above the beach level. Glacial drift is often composed predominantly of the local material immediate beneath the ice. So where the drift up to this point on the walk was sandy reflective of the underlying sand it now is boulder filled reflective of the underlying bedrock.

Bouldery basal till

At this point the walk reaches the bedrock exposed at Nodule Point. It is aptly named. The point was originally named Nodule Point by British explorer George Vancouver. The American Wilkes Expedition named it Ariel Point. However, the U.S. Coastal Survey went with the more descriptive name of Nodule Point.

Concretions at Nodule Point

The concretions range up to sizes a bit larger than bowling balls and most are round. The concretions form as a result of different cementation often because of impurities within the sand or siltstone that act as nucleation sites for carbonate to precipitate. Small bits of mud stone surrounded by harder rock are present within this formation. As the rock is eroded, the harder cemented sections stand out as hard knobs from the surrounding softer rock. These concretions are very common in the sandstones in rocks in this area, but this is one of the better sites for observing them. To be clear these geologic features are concretions not nodules. Nodules involve actual replacement of the parent material with new minerals.

Concretions with quarter coin.

 

Small concretions and vein-like concretions

The formation is primarily sandstone of Eocene age (roughly 45 million years) and was described named the Scow Bay Formation by Allison (1959). Scow Bay is located along the southwest coast of Marrowstone Island. The formation likely overlies the Crescent Formation basalts and was deposited near the end of the Crescent basalt lava flows. Uplift of the formations is the result of accretion of ocean sediments and up lift of the Olympic Mountains approximately 7 to 12 million years ago.

An intriguing feature of the bedrock on Marrowstone Island is that bedrock is found along the shores south of the hamlet Norland, but to the north the depth of bedrock is greater than 1,500 feet with no wells penetrating to the bedrock suggesting a major preglacial structure that happens to align in a parallel manner with faults to the east suggested on Whidbey Island. 

It is well worth going a little bit further south past the point. A few hundred feet to the south a 20 foot wide vertical dike of basalt intrudes through the sandstone. The dike is likely associated with a late stage of volcanism associated with the massive out pouring of magma of the Crescent Formation basalt that underlies large tracts of land along the north and east side of the Olympic Peninsula. One of the interesting features of this dike is how the heat from the magma altered and hardened the sandstone on either side of the dike. The harder sandstone along with its concretions juts further out from the land and depending on the tide may require getting wet to get past like I had to the day I did the hike. Which suggests that doing the hike during

low tide is preferable.

Basalt dike with hard altered sandstone on either side.

Chill zone next to basalt dike on the left.

Basalt dike

Altered sandstone with concretions is harder and protrudes out into the water

If you do this walk you may want to continue to the south to Liplip Point where lip shaped concretions are common and on occasion some good birding as well Earlier Post I have been to Nodule Point on five occasions and have never seen anyone there. A few people will be around the beach near the county park depending on the weather. But even then the beach traffic can be interesting. Lots of deer use the beach as a trail and on this trip I nearly stepped on a seal pup as I was looking at the geology and not where I was walking. It can be also be a great spot for watching ship traffic as this is the passage into Puget Sound.