Major landslide in the state of Washington, USA: UPDATE(S)

Oso, Washington, is at the marker. Arlington is to
the left, Darlington is to the right by the magnifier bar.
The slide at Oso cut off Highway 530 between
Arlington an Darlington.

**Chapter 4 in my book "The Dynamics of Disaster" is titled "The Flying Carpet of Elm" and discusses the factors that influence landslides. It also discusses the mother of all landslides, a slide that occurred 50 million years ago in Wyoming, covering 1300 square miles and traveling more than 30 miles.

Monday a.m. Update and correction: The Seattle Times reports "108 reports of missing people." CNN.COM has reported "Washington landslide: 8 dead, 108 missing." Emergency managers are saying that they have a list of those reported missing but that it does not mean all of them were killed. I thank a Washington reader for pointing out this difference.

Cliff Mass has a post on March 24 that describes the meteorological conditions leading up to the landslide.

The SeattleTimes is providing excellent coverage.

Take I-5 north from Seattle about 50 miles through Everett toward Arlington, and turn east onto Highway 530, which takes you south of Mount Baker. Along this road is the small town of Oso, population about 200. At about 11:00 this morning, a massive slide of mud, rocks and trees travelled a mile down near Oso, taking down at least 6 homes, killing at least three people and trapping others. (As of Monday morning, 18 are still missing.) Three more are reported in critical condition.The slide was at the 29400 block of SR 530 near milepost 37, between the cities of Arlington and Darrington. It landed in the path of the Stillaguamish River, reducing its level at one spot from about 3.1 feet to 0.9 feet, indicating that the slide appreciably blocked the river. The state hydrologist reported that 15-20 feet of debris blocked the river, and that its flow had been reduced to about 1,000 cubic feet per second. Other reports have said that the slide is 135 feet and 180 feet deep.

Image of the landslide from Seattle Pi

     In situations like this where an earth slide blocks a river, the concern is that water will pond behind the blockage forming a lake, and that the blockage--a dam--will suddenly collapse and release the water catastrophically. The National Weather Service has said that for this to occur the water would have to be blocked for 36 hours, and then released within an hours time.
     Snohomish county officials have advised residents downstream of the slide to evacuate their homes as "It is going to break loose and the question is how and where" (John Pennington with the Department of Emergency Management (quoted from King5 news here).
     The National Weather Service has issued a flash flood watch through Snohomish County through Sunday afternoon. The ground is saturated with water from recent rains, flash flooding is possible, and the saturated ground combined with rain is believed to be the cause of the Oso mudslide. Flood alerts have been issued both upstream and downstream of the slide.

Image showing the abundance of water at the base of the slide.
From Seattle Pi

     UPDATE: Several serious hazards remain in this area. The first is the landslide material itself. It is composed of a lot of fine grained materials, sand and clay, that form a nasty, hazardous substance called "quick sand" or, depending on particle size, "quick clay." Quick clay was the cause of the landslide from which the title of my book chapter, The Flying Carpet of Elm, was taken. I'm not sure of the exact geology of the Oso area, but it looks like the materials are a watery mixture of very fine particles. These materials, if undisturbed, can be very strong, forming the slopes on which homes and other buildings were built in the area. But, when disturbed, in an instant under certain conditions of stress, the state of the materials changes to liquid. Although some of the water visible in the images (to the right) may be from the dammed river, it looks like a lot of the water came from within the landslide itself.
     The second major hazard arises from the partially blocked river. These landslide dams are not strong and eventually, sooner or later, the water will either erode through the toe of the dam (the best outcome) or the dam will break (worst outcome). Until equilibrium is restored, downstream residents and infrastructure are at risk. Apparently a major bridge on Highway I-5 is being watched carefully because the pilings holding it up are old and not as deep as would be built under newer bridges.

Here are more references from Dave Petley's AGU Landslide Blog.

Happy Pi Day!

Young folks celebrating Pi Day at San Francisco's
Exploratorium. Photo from CNN.com here.

When I saw the wonderful faces of these students celebrating Pi day at the, yes again I'll use the word, "wonderful" Exploratorium in San Francisco, my mind went back to life in the 1950's and the science teacher who inspired me. So, I thought that I'd put up a photo of a 9th grade exam that I've saved all these decades, and hope that these kids get the inspiration that I got from that teacher (in spite of the fact that I wasn't a boy and couldn't be made a knight!!).
     It was 1959, the space race was in full swing, and mimeograp'ing was the technology of the day for producing student exams.  This was a general science class and was one of the physics components. The purple ink questions have long faded away, but perhaps you can guess them from the answers:

velocity
acceleration
32 ft/sec^2
32 ft/sec^2
100 ft/sec
neither
same
(1/2 provided your initial velocity is zero)
vector
320 ft/sec
160 ft/sec
1600 ft
200 sec
49,000 m
980 m/sec
102.4 ft/sec
100 lbs
37 degrees
45 degrees....

Then there is the comment: "You deserve a medal. If you were a boy you should be made a knight." Gzsh,
shouldn't have at least told me I could be a Dame?

And, in pencil on the left
side of the astronaut sketch written
a bout ten years later when I
had done an internship at NASA,
someone wrote in "An official of
the NASA says there are no
provisions as yet for a woman
astronaut. The exploration
rockets, however, he says,
do provide for 120 pounds
of recreational equipment."

Times have changed, kids, go for it
on Pi Day!! You are great!

Corvettes and sinkholes: what is a sinkhole?

1962 Black Corvette
from Roscoe-Restoration.com

A few weeks ago, a sinkhole swallowed eight valuable Corvettes at the National Corvette Museum in Bowling Green, Kentucky, and today the news is that the recovery of the cars has started. Here, from CNN.com, is a list of the cars:

-- a 1962 "Black Corvette"
-- a 1984 PPG pace car
-- a 2009 ZR1 "Blue Devil"
-- the 1992 white "1 Millionth Corvette"
-- a 1993 ruby red "40th Anniversary Corvette"
-- a 2001 Mallett Hammer Z06 Corvette
-- the 2009 white "1.5 Millionth Corvette"
-- a 1993 ZR-1 Spyder

The museum estimated millions of dollars in damage. The sinkhole was approximately 40 feet in diameter and 20 feet deep.
    What causes sinkholes? A glimpse at this fascinating map of Kentucky groundwater flow routes confirms the well-known fact that sinkholes are not uncommon there, given features with such names as "Sinking Creek", "Auburn Bluehole," and "Lost River Rise."

Simplified geology of Kentucky
from Geology.about.com.

     Bowling Green lies in the south-central western portion of Kentucky in rocks of Mississippian age (359-323 million years ago; comprise about the lower (oldest) 2/3 of the Carboniferous rocks). In Kentucky, the Carboniferous Series rocks (359-299 m.y. ago) contain massive amounts of coal, and are so abundant that they are subdivided into the Mississipian and Pennsylvanian. They are the thickest in the Appalachian Basin in the eastern portion of Kentucky, and the Illinois Basin in the west.
      The Mississipian rocks of western Kentucky are comprised mostly of limestones, shales and sandstones. The limestones contain a oil reservoirs underground and where exposed at the surface, the limestone is quarried--the Reed quarry producing more limestone than any other quarry in the U.S. The limestone also includes Mammoth Cave, part of the Mammoth Cave-Flintridge system, the longest cave system in the world. These limestones were deposited in shallow seas.

Karst features from UTexas here.

     Limestone is dominantly composed of calcium carbonate, CaCO3. This mineral is quite soluble in water containing CO2 through the reaction:

CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂

There is a similar reaction for aragonite, a magnesium containing carbonate that is another common component of limestone. The dissolution of calcite and aragonite produces caves underground. The caves are often connected through fissures leading to extensive networks. As the dissolution proceeds over time, the caves approach the surface and when the surface rocks or soils can no longer support the load of trees or human structures, they collapse, producing sinkholes. Notice also the sinking streams on the illustration, and the name of the stream "Sinking Creek" mentioned above.