Thursday, May 28, 2015

Possession Point Landslide: Fluid Landslide in the Summer

 A bit of follow up on the landslide shown in yesterday's post. The emphasis of the post was that large run outs on tide lands tend to get erased and thus the scale of the risk might be missed with the lack of evidence.


But there is another feature of this slide that can be missed, but is also of some importance. Note the trees on the slope outside the slide area are covered with leaves. The slope is mostly forested with red alder and big leaf maple. This large landslide with very fluid behavior took place in the summer. 

Tuesday, May 26, 2015

Old Landslide Run Outs on Whidbey Island

I have been assembling some geology maps and landslide data and came across a couple of mapped landslide deposits on maps. The first was a map by the USGS of the Mukilteo Quad showing the dashed outline of a landslide extending well out onto the tide lands on the shoreline of Whidbey Island. 

Map by Minard (1982)

There is an image of this slide included in a map produced by Kueler (1988) on coastal erosion.  

1979 image of slide (Photo: Dave Frank, USGS #0128_59)

The deposit is now long gone and hence the landslide run out distance from the landslide off this bluff has been erased.

2014 Google earth image showing entire landslide deposit is gone from shore 

The Maxwelton Quad map (Deither and others, 1981) has a similar peninsula of landslide debris mapped onto the tidal area along the shore. Again no evidence of the slide deposit remain of this slide either other than the scar on the bluff itself.

Map by Dethier and others (1981)


Monday, May 25, 2015

New Rail Yards at Northwest Refineries

Changes in fossil fuel activity have and continue to be a subject of some interest in Washington State. The latest are protests as well as legal wrangles associated with Shell Oil and Arctic Ocean drilling equipment in Seattle and Bellingham.
 
And of course there are the trains - both oil and coal. The northwest Washington refineries have all expanded their rail facilities the past couple of years in order to handle rail shipments of oil.
 
BP refinery in Whatcom County 2011

2014 image shows the new rail loop to the northeast

ConocoPhillips Whatcom County 2011

Rail spur added to the south 2014

Anacortes refinery 2011

Rail spurs added on the west side 2014 image

The rail expansion has been a big rapid change for the northwest Washington refineries and brought oil to the refineries in a manner that was a rather large change to rail traffic. The expansion of oil unit trains in Washington took place while hearings on coal terminals were attracting attention to rail traffic impacts. As accidents happened elsewhere involving the explosion of volatile oil rail cars, more attention has been brought on oil trains.

The rail oil shipments shown above are not limited to the local refineries. All three of these refineries have port facilities that allow loading of the oil on barges for shipments to other refineries on the west coast and other oil terminal sites have been proposed besides simply the refineries (bakken-oil-continues-moving-to-the-pacific-northwest).

The land foot print of rail lines at the refineries is rather small compared to the foot print where the oil is coming from (notes-on-coal-dust-and-bakken-oil).

Thursday, May 21, 2015

House Bill 1137 Tries to Exempt Geologists From Well Licensing

A little policy wonk stuff.

House Bill 1137 was introduced this legislative session would include licensed geologist as exempt from licensing associated with water well construction. The current exemptions include:

Any individual who personally constructs a well on land which is owned or leased by the individual or in which the individual has a beneficial interest as a contract purchaser and is used by the individual for farm or single-family residential use only

and

a person who is a licensed architect,
a licensed professional engineer,
or a licensed professional land surveyor.

Geologists are not exempt so can't do any water well work.

Kind of a strange situation since geologists are routinely charged with determining how and where wells should be constructed. The Washington State Groundwater Association raised some concerns in opposition to the bill. Understandable in an effort to protect their industry. They suggested sending this issue to the Well Construction Technical Advisory Group (WCTAG).     

The committee hearing can be heard HERE. The bill appears to be on pause and likely will not see any action this year.

I have no involvement in this issue, but will offer the view that if the law on well licensing is going to exempt anyone, geologists are probably the most qualified to be exempted. Would be a good subject for the WCTAG to take up; however, that group did sort of mess up on a rule a few years ago that required a legislative fix in that they defined test pits as wells during rule making. 

Monday, May 18, 2015

More on Weathered Quimper Sandstone

Last week I noted a small natural bridge within the Quimper Sandstone (quimper-sandstone-notes). In my notes I speculated as to the source of the more weathered rock. Callan provides another possible and I think very reasonable explanation (spheroidal-weathering-in-sandstone).

There is plenty of spheroidal weathering within the Quimper Sandstone at the one- to two-foot scale. But as Callan's image shows, the scale can be much larger and the scale in the Callan image is very similar to the scale I observed.

Regardless, of the actual source of the preferential weathering, the deep weathering of the Quimper Sandstone at Oak Bay in presents some slope stability issues. Most bedrock lined shores of the Salish Sea are viewed as stable with very low erosion rates; however, the deeply weathered bedrock here is more readily eroded than some of the glacial sediments. In addition, the deep weathering has caused some areas of deep-seated sliding that may be related to the deep weathering.

Deep level sliding below the root zone is not unusual in deeply weathered bedrock and is indeed a problem in southwest Washington State. What is a bit unusual about this area at Oak Bay is that this area was glaciated but the glacial ice did not strip off the weak weathered rock at this spot. 

 

Thursday, May 14, 2015

Notes on a Few West Coast Bathymetry Features

Taking a look at bathymetry off the west U.S. coast one can see and contemplate the ocean floor features some of which have been side scanned to remarkable resolution.

Ocean floor off northwest Washington Coast
 
Strait of Juan de Fuca in the northeast of image has a clear link to a current pathway that funnels water currents down to submarine canyon. Other submarine canyons pull sediment via density currents to the deep ocean floor to the west. The ridges on the lower slope above the deep ocean floor are the result of the under thrusting of the ocean floor under the continent. These ridges are the expression of the mega earthquakes of the past as well as a telling indicator of what we might expect in the future. 
 
Ocean floor off southwest Washington coast
 
The estuary of the Columbia River is on the southeast part of the image with Willapa Bay to the north. Several prominent canyons and even a fan on the deep ocean floor from the Columbia. The off shore thrust ridges are also prominent.
 
Northern California coast

There are still prominent canyons off the California coast, but note the ridges are not present. No subducting plate here. California has a different fault regime - strike slip along the San Andreas system.

Mendocino Fracture Zone is the sharp east-west ridge
 
The Mendocino Fracture Zone marks the boundary between the convergent plate boundary to the north and the strike-slip boundary on the south. The north-south ridge extending from the fracture zone is the ocean spreading ridge off the northern California coast - the Gorda Ridge with the Gorda ocean plate to the east of the ridge and the Pacific Plate to the west. The Gorda ocean plate is decidedly not smooth reflecting internal deformation within the plate perhaps the result of its being in a bit of bind between larger plate motions.

One of the striking things of the Mendocino Fracture Zone is the ocean floor to the south is much deeper. This is a significant factor in how tsunamis are transmitted to the coast that creates a rather unfortunate circumstance for Crescent City, California by focusing wave energy towards the California coast at that location.

A bit a field from the Washington coast but something to consider in the concept of accreted terranes (of which Washington is full of) is a set of ocean seamounts off the central California coast - Taney Seamounts. This is a set of basalt volcanoes described by Clague, Reynolds and Davis (2000). The studies have produced some relatively high resolution bathymetry of these seamounts as well as a few other volcanic seamounts not directly associated with spreading ridges or hot spots seamounts.

This set of peaks would present a bit of a problem if they encountered a subduction zone. Something to consider when contemplating accretion complexes.

Wednesday, May 13, 2015

Quimper Sandstone Notes: Petrified Wood and Fossils at Oak Bay

No rest after being away so right back into the "field". One of my ventures took me to the west shore of Oak Bay. Oak Bay is south of Marrowstone and Indian Islands and was so named because of a stand of oak trees along the south shore of Indian Island where the Vancouver Expedition entered the bay. The oaks are still there in a county park along the south shore of Indian Island (Indian-island-Jefferson-County)

A fair bit of the west shore of Oak Bay is bedrock of the Quimper Sandstone and forms a bedrock platform beach with a covering of cobbles. 

Platform beach of bedrock

I came across a few fossils within the sandstone. The sandstone has been dated as Eocene based on forams studied by Arementrout and Berta (1977) which puts this unit in roughly the same time period as the Crescent Basalt.






Within the same outcrop that contained the snails and clams I noted a bit of wood sticking out of the rock. I have seen bits of carbonized wood and sticks in the Quimper before and in similar sandstones of similar age nearby on Marrowstone Island. But this stick was a bit of petrified wood.


Further along the shore I came across a small hole in the rock. A vertical vein of some sort of deeply weathered material has preferentially eroded creating a small hole in the rock. I suspect this might be a old clastic dike of silt that has weathered to clay but the weathering made it difficult to figure out the original rock type.

Armemtrout, J.M. and Berta, Annalisa, 19977, Eocene-Oligocene foraminfera sequence from northeast Olympic Peninsula, Washington: Journal of Foraminiferal Research, v. 7, no. 3, p 216-233.