Salmon win! A 12 story dam removed on the White Salmon River

Condit Dam seconds after a blast has opened
a gaping hole at the base on 10/26/11.
PacifiCorp via AP photo from here.

The 125' tall Condit Dam was installed across the White Salmon River in 1913, a 12-story high dam that prevented salmon from migrating back to their habitat and closed fisheries to the Yakama Nation for nearly 100 years. Yesterday part of the dam was removed by blasting.  Here's a beautiful video prepared by Stella and Emily Washines, with beadwork telling part of the story.

The Condit Dam is the second-tallest dam to be demolished in U.S. history, and it provided power for about 7,000 homes but the owner, PacificCorp elected to remove it rather than install expensive fish passage structures that would have been required for relicensing. The dam removal project will cost about $32 million when restoration of the valley is completed--and restoration will be needed as you'll see from the video below.

Prior to the blasting, work crews created an 18 foot wide, 13 foot tall tunnel in the base of the dam. A layer of silt about 50 feet high had accumulated in the lake, Northwestern Lake, behind the dam.

Here's a video of the actual event. Nothing happens for a minute (so you can keep reading this while you are waiting, but it's worth the wait!) Watch at the very base of the dam at about 1 minute 17 seconds into the film-- you can see a small atmospheric shock wave and steam cloud formed by the explosion that triggers a massively high-pressured jet. By breaching the dam at the bottom, sediment is removed from the base of the reservoir and yet the dam remains to be removed by heavy machinery at a later time.   It may be my imagination but at about 1'27" it looks like branches in front of the camera start moving because of wind generated by the atmospheric shock and the violent flow.  At about 2:15 there's a nice shot of the jet at the base of the dam with sediment coming out on the bottom and clear water on the top, a stratified flow.

(There are 3.3 miles of the white Salmon below the dam---No need to feel sorry for any luckless salmon that happened to be trying to return to spawn on this day....Fisheries biologists captured and relocated 679 tule chinook from below the dam to protect their spawning nests from the sediment removed from the reservoir. )

Removal of the dam will open 33 miles of habitat for steelhead after the restoration, and restore the White Salmon River for white-water rafting. Other dams in the process of removal and restoration are the 210-foot Glines Canyon Dam and the 108 foot Elwha Dam, both on the Olympic Peninsula.

Major flooding in Bangkok

NASA MODIS image from Terra satellite, October 25, 2011

Bangkok, Thailand, is experiencing extreme flooding. To our friends there, stay dry and stay safe! We're thinking of you!

The flooding has been building for three months. The flood waters are expected to rise to as much as 5', and the highest tide of the year is to come this weekend, backing up the rivers.  The average elevation of bangkok is less than 6'. The Thai prime minister has declared a five-day public holiday in affected areas (21 provinces including Bangkok) in an attempt to get people to seek safety away from the city.  The Chao Phraya River which winds through the capital is likely to top its embankments this weekend.  The domestic airport, Don Muang airport, is closed because floodwaters flowed onto the runways and affected lighting. Domestic flights are being rerouted to Suvarnabhumi Airport.  The floods have killed 373 people and affect 9.5 million. This is the worst flooding in a half century and may continue for a month as the water drains out through the cities 1,682 canals to the rivers.

NASA MODIS image, November 13, 2008

In some places, the water approaching the city is 10' deep. It may have inundated 10,000 factories north of the city, disrupting supply chains for Apple and Toyota. Thailand makes about 1/4 of the world's hard disk drives and is a production hub for Japanese carmakers and electronics firms. The dikes holding back the floods have not been tested by floods of this size and so it's uncertain whether they can withstand the pressure of 10' deep water. An advisor from the Netherlands has said "Any dike system that comes under extreme conditions will show failures."

It is estimated that the flooding will cut about 1 percentage point from economic growth, and the budget for rehabilitation may exceed $3.2 billion.

The summer monsoon (August to October) is the culprit here.  Here's a site that gives a good overview of the monsoon meteorology in Thailand.

Fantastic Northern Lights! A rare red aurora last night.

The aurora in Arkansas, USA
Photo copyrighted by Brian Emfinger
Permission to use has been granted.

Last night we were out running errands around 6:15 and I commented to my husband that the sunset looked unusual. It was a brilliant orange in the west, but only over a fairly small area, didn't seem big enough to light up the whole sky. But, in the east, the clouds were an unusual pink color. Unfortunately, though I had my camera in the car, I didn't take a shot because there wasn't a "perfect" setting (the Champaign airport is not the prettiest foreground for such a shot), and so other than my comment, I have no record of this event that turns out to probably have been the first aurora that I've seen!

I was therefore surprised to get up this morning and read about the magnificent aurora that filled the sky around that time! The aurora was caused by a coronal mass ejection (CME) two days earlier. It can be viewed here http://www.spaceweather.com/images2011/22oct11/cme_c2_strip.gif.

More discussion about this event can be found on spaceweather.com, which also has a great collection of pictures from places as far south as New Mexico.  The aurora was one of the fairly rare "red" ones.

Auroras are produced when electrons and protons from a CME interacts with the earth's magnetic field, generating electrical power. The discharge can be though of as a great big neon sign in the sky.  Gases give off photons, light, when subjected to an electric field. Green auroras with a reddish lower border are fairly common, and originate at an altitude of about 60 miles above the earth. Red auroras are much rarer, and occur much higher in the atmosphere, 180 to 300 miles.  They are associated with a large influx of electrons that move too slowly to penetrate deep into the atmosphere. At this altitude, the electrons lose their energy to oxygen atoms. The light produced is at a wavelength of 6300 and 6364 Angstroms on the spectrum, a true red color. Details of the process are still a mystery.

Here's a post that I did a year ago on solar flares and Newt Gingrich.

The Chicxulub impact--What happened on the opposite side of the earth?

Artist impression of Chicxulub impact.
Artist unknown.

A number of researchers have asked "what happened on the side of the earth opposite the place where the meteorite hit in the Yucatan (Mexico) 65 million years ago?" This point is called the "antipode." The earth is a sphere, and acts like a lens to focus seismic waves on the opposite side of the planet. Body waves travel through the interior and are focused by reflection and refraction off of boundaries such as the crust-mantle, mantle-outer core, etc. Surface waves converge at the antipode after spreading out from the impact site, which looks like a point source of energy at the scale of the whole earth. Models to date have used  a spherically symmetric earth and did not include subtlties such as the elliptical shape of the earth or continents. These models have suggested that there could have been at least 10 meters (33 feet) of shattered uplifted rocks at the antipode.

 In a new paper in the October 2011 issue of Geophysical Journal International, Meschede et al. have combined a detailed 3-D model of the earth's interior and crustal structure with numerical calculations of the propagation of seismic waves around the earth after an impact.*** They model the impact as a single-force point source from the impact of a stony meteorite 20 km in diameter impacting at 20 km/sec.  They use a Gaussian source-time function to model the duration of the event, and assume that 0.001 to 0.0001 of the meteorite's energy ends up in the seismic waves that propagate away from the point of impact. In their model, the earth has a solid inner core, fluid outer core, ellipticity, topography and bathymetry, oceans, and rotation. The average node spacing is 10 km (this must have been done on a humongous computer!).  Since the continents were in different positions 65 million years ago, they chose an impact position to mimic it's position relative to the Eurasian and American continents at that time. The ancient antipode position was north of Australia. 

They found that it takes about 1.5 hours for the waves to reach the antipode.  The maximum displacement was calculated to be 4 meters, less than half that of the older models.  The structure of the displacement field is not symmetric, but has a starfish rayed shape because of heterogeneities in the crust, such as the thick seismically slow crust of the Andes.  In vertical cross section down to the base of the mantle, there are "chimneys" of peak stress, regions where stresses are concentrated.

A number of researchers have asked "what happened on the side of the earth opposite the place where the meteorite hit in the Yucatan (Mexico) 65 million years ago?" This point is called the "antipode." The earth is a sphere, and acts like a lens to focus seismic waves on the opposite side of the planet. Body waves travel through the interior and are focused by reflection and refraction off of boundaries such as the crust-mantle, mantle-outer core, etc. Surface waves converge at the antipode after spreading out from the impact site, which looks like a point source of energy at the scale of the whole earth. Models to date have used  a spherically symmetric earth and did not include subtlties such as the elliptical shape of the earth or continents. These models have suggested that there could have been at least 10 meters (33 feet) of shattered uplifted rocks at the antipode.

Peak displacements in the impact hemisphere (left) and the antipode (right).

 In a new paper in the October 2011 issue of Geophysical Journal International, Meschede et al. have combined a detailed 3-D model of the earth's interior and crustal structure with numerical calculations of the propagation of seismic waves around the earth after an impact.*** They model the impact as a single-force point source from the impact of a stony meteorite 20 km in diameter impacting at 20 km/sec.  They use a Gaussian source-time function to model the duration of the event, and assume that 0.001 to 0.0001 of the meteorite's energy ends up in the seismic waves that propagate away from the point of impact. In their model, the earth has a solid inner core, fluid outer core, ellipticity, topography and bathymetry, oceans, and rotation. The average node spacing is 10 km (this must have been done on a humongous computer!).  Since the continents were in different positions 65 million years ago, they chose an impact position to mimic it's position relative to the Eurasian and American continents at that time. The ancient antipode position was north of Australia. 

They found that it takes about 1.5 hours for the waves to reach the antipode.  The maximum displacement was calculated to be 4 meters, less than half that of the older models.  The structure of the displacement field is not symmetric, but has a starfish rayed shape because of heterogeneities in the crust, such as the thick seismically slow crust of the Andes.  In vertical cross section down to the base of the mantle, there are "chimneys" of peak stress, regions where stresses are concentrated.

The calculated stresses from the impact are comparable to stress drops observed in moderate to large earthquakes, prompting the authors to speculate that there could have been earthquakes in response to the seismic waves propagating away from the impact.

The calculated stresses from the impact are comparable to stress drops observed in moderate to large earthquakes, prompting the authors to speculate that there could have been earthquakes in response to the seismic waves propagating away from the impact. They say that the stresses are probably large enough to trigger volcanism, and that the seismic waves are large enough over areas of the ocean to induce tsunamis.

***Meschede, M.A., Myhrvold, C.L., and Tromp, J., Antipodal focusing of seismic waves due to large meteorite impacts on Earth, Geophysical Journal International, 187, 529-537, 2011.

"Flash heating" as a mechanism for fault weakening during earthquakes

The San Andreas fault
USGS photo

One problem that has mystified seismologists and geophysicists for a long time is the lack of high heat flow over active fault zones. When rocks are stressed in laboratory experiments, data indicate that faults should be very strong, and theories suggest that when they fail during an earthquake, frictional heating should create high temperatures. But, that is not observed on faults like the San Andreas in California.  A variety of laboratory experiments over the past decades have suggested that rocks are actually very weak under conditions of fast sliding that are occur in earthquakes.

In a paper*** in this weeks Science, Goldsby and Tullis point out that when two rock surfaces are brought together, they only touch at a few small contact points compared to the total surface area. These points have average sizes of tens of microns. Like the floor under a spiky woman's high heeled shoe, the stresses are concentrated on these points, typically having local stresses of 10 GPa for even modest average stresses. When these microscopic contacts are sheared in an earthquake, very high temperatures can result.  If the shearing rate is slow, heat can diffuse away from these points and the temperature remains low. However, if the shearing rate is high, there is no time for diffusion and the temperature at the points increases, sometimes to melting temperatures.

The results are based on laboratory experiments on a number of different rock types.  In these experiments rocks were sheared past each other at velocities up to 0.4 m/s over distances up to 45 mm. The results showed that the friction coefficient decreased dramatically when sliding velocity exceeded about 0.1 meters per second. Visual inspection of the samples after the sliding experiment showed that a thin layer of gouge (melted rock and crushed rock) had formed. The gouge layer was less than 30 microns thick.

The authors propose that flash heating is the dominant mechanism of weakening in small-slip, small-magnitude earthquakes, and that it is likely to be the dominant mechanism determining the strength of a fault in the early stages of larger earthquakes.  During continued slip during large earthquakes other fault-weakening mechanisms may combine with or dominate over flash heating, such as melt lubrication, gel formation, or pore-fluid pressurization.


***Goldsby, D.L., and Tullis, T.E., Flash heating leads to low frictional strength of crustal rocks at earthquake slip rates, Science, 334, 216-218, 2011.

Monster haboob in Texas--be glad you weren't flying into Lubbock!

October 17, 2011 haboob in Lubbock, Texas
from http://www.youtube.com/watch?v=wfuDFEZYHTE,
as printed in the Washington Post

A haboob is a giant plume of dust that can extend thousands of feet into the atmosphere. They are common in desert environments, and with the drought in Texas this year there's lots of dust to blow around.  A cold front went through the Texas panhandle yesterday with wind over 60 miles per hour. They often form from downdrafts of approaching thunderstorms, but in this case the winds of the cold front alone were sufficient to kick up the storm.  Cars were forced to stop on highways, and FAA controllers at Lubbock International Airport had to evacuate. Haboobs can be 100 km wide, and they can travel up to 100 km/hour (60 mph). If there is rain mixed into them, they become mud storms.

Probably the best video I've ever found on haboobs is this one from the July 5th, 2011, haboob in Phoenix. This Phoenix haboob was produced by downdrafts associated with a monsoon thunderstorm. As with Texas, Phoenix has been in a drought and so there was enough dust to make the haboob exceptionally intense.

Haboob is an Arabic word for "strong wind."

Firefighters nightmare: backdraft explosion

A backdraft explosion from The Gray Monk

Today's CNN news reports on a backdraft explosion at a fire in Ohio. This type of explosion can occur when an oxygen-starved fire suddenly gains access to oxygen, for example when a window breaks or a door is opened. It is a dangerous and well-known phenomenon for firefighters.  An oxygen starved fire produces combustible gases, primarily carbon monoxide, and smoke.  When these gain access to oxygen, combustion can take off again raising the temperature of the gases. Because they heat up, they expand, often extremely rapidly.

As the smoldering fire sucks in oxygen, there is often a "puffing" effect as the fire gets a little, but not enough, oxygen.  As the fire puffs, smoke produced by the fire is often sucked back into the burning area, giving rise to the term "backdraft." Firefighters are taught to avoid these dangerous situations, and to attempt to deal with it by ventilating the fire from the highest point. This allows the heat and smoke produced when the combustion reignites to escape through the highest point without exploding.

Wiki is full of all sorts of interesting trivia! There was a 1991 film "Backdraft" in which a serial arsonist was using backdrafts as a means for assassinating people! Also, if your house burns down and you've got papers stored in a safe--don't rush in to open it!! After the 1906 San Francisco earthquake and fire, business people who opened warm safes to recover their unburned papers exposed the hot gas of the interiors to an oxygen source, immediately and explosively setting the papers on fire!