Typhoon Mekkhala (Amang) and Pope Francis's visit to the Philippines

Typhoon Mekkhala at 2 p.m. Eastern Time Friday
3:00 a.m. Saturday local time in Manila
from CNN.COM

The image at the left was taken approximately six hours before Pope Francis is to fly into Tacloban (see location) to conduct a mass before tens to hundreds of people at 9:30 a.m. local time (8:30 p.m. Friday night ET). CNN is describing this as "likely to be a soggy, windy experience with a measure of peril." Between 13 and 15 cm of rain are forecast (Tacloban and Manila, respectively, more at places nearby). He is scheduled to hold a mass on Sunday morning that as many as 6 million people have been projected to attend, though flooding and landslides may make travel dangerous and difficult. As of this writing, Vatican officials have commented to the press.a

Projected rainfall over the next 48 hours in millimeters.
From the CNN article cited.

     According to AccuWeather.com, Mekkhala's trajectory is most likely to spend the weekend in the central Philippines spreading very heavy rain as it moves slowly to the west northwest. Landfall is likely in Samar, one of the areas hit hard by Super Typhoon Haiyan (Yolanda) only last year. Part of the Pope's schedule is to take him to the eastern Visayas to visit with people impacted by Haiyan.
     Although this is significant and disruptive rainfall, it is an order of magnitude less than the heaviest rainfalls recorded in typhoons. In August 2009, Typhoon Morakot dropped 2900 mm (114") in Taiwan three days. This included the highest, single-day regional record at 1403 mm (55 inches). The damage to infrastructure from flooding and slides was enormous.
    Such heavy rainfalls have not gone unnoticed by people who study earthquakes. Seven months after Typhoon Morakot dropped this rain, a M6.4 earthquake rattled Taiwan. According to Shimon Wdowinski and I. Tsukanov, as reported by Richard Lovett of National Geographic Magazine, heavy rainfall may be triggering these earthquakes. (Note: I could not find a peer-reviewed paper from them, only an AGU 2011 Fall meeting abstract#U53E-06). The M7.0 earthquake in 2010 in Haiti came 18 months after it had been deluged by two hurricanes and two tropical storms. There are difficulties in making correlations between events so far apart in time, and for which there are only a few data points:

• 2009 Typhoon Morakot, M6.2 in 2009 and M6.4 in 2010
• 1996 Typhoon Herb, M6.2 in 1998 and M7.6 in 1999
• 1969 Typhoon Flossie, M6.2 in 1972

But, Wdowinski's analysis suggested that Taiwan's M6+ earthquakes were five times more likely to occur within four years after such storms than if the storms had no effect. Wdowinski suggests that is not the weight of the water that triggers the earthquakes, but the unloading of the crust by landslides and sediment redistribution from the land into the sea. This lightens the stress on the crustal rocks and, if a fault is near failure, makes it easier to slip, that is a typhoon alters the timing of an imminent earthquake. The AGU abstract says that mesh free finite element modeling and Coulomb failure stress analysis were used to calculate the increase in failure stresses at the hypo centers by 300-1500 Pa, ultimately triggering the earthquakes. The say that the statistical analysis indicated "a very low probability (1-5%) for a random earthquake occurrence process to give the observed typhoon-earthquake correlation.
    A slightly different model was proposed by Thomas Adar for the Himalayas. In the monsoon seasons, water flows from the Himalayas into the lowlands where its weight causes a slight bending of the Indian tectonic plate causing the edge of the plate to deform slightly. During the wet season, the bending offsets the tectonic strain on the fault caused by the plate motions and reduces the short-term risk of earthquakes. But, in winter, when the lowlands dry out, the plate unbends and the earthquake rate increases.

Indian Ocean tsunami--not 2004, but 1945

The Makran subduction zone showing the approximate
source of the earthquake (yellow) that caused
the 945 tsunami (inferred from seismogram and
coastal uplift). Sites with blue circles show locations
of tsunami fatalities. Red dots show locations of
survivors who were interviewed, and fractions
show the fraction of credible first-hand accounts
(denominator is total number interviewed). From the
article referenced in the text.

Eos, Transactions of the American Geophysical Union features an article in the December 23 issue by D.M. Kakar and others about the next-to-last devastating tsunami in the Indian Ocean (on the 10th anniversary of the most devastating 2004 tsunami). Eos, by the way, is now freely available online to everyone at Eos.org, not just members of the AGU.

     Documentation of this earthquake and tsunami was hindered by the international instabilities of World War II and British India. This article is the result of an effort to find the aging survivors of the event and gather eyewitness accounts in order to improve tsunami hazard models and awareness. 

     The earthquake that caused the tsunami was M8.1 and centered west of Karachi (Pakistan) along the Makran subduction zone where the Indian Ocean plate is subducted below the Eurasian plate at a rate of about 4 cm/year. Estimated fatalities are between 300 and 4000, most in the areas of Pakistan, Iran and Oman shown on the map, but thirteen deaths in Bombay (Mumbai). Elders in Oman, Iran, Pakistan and India were interviewed. Most were children in 1945. Although many accounts were "hearsay", others contained details assumed to be real: "For example, the shaking in Ormara brought down a stone house that entrapped one eye-witness's recently married sister. The noisy approach of a wave in Pasni cut short the predawn Fajr prayer. The sea at Konarak entered a mosque and injured some who were praying there...."
     The authors of this article hope that the eyewitness accounts can be used to constrain models of tsunami hazards, and that the eyewitness stories will help educate those who live along the shores about tsunamis.  

Happy Holidays!

As 2014 winds down and the holidays approach, here again is the Bill and Boyd reminder that Nature doesn't always know about and respect holidays! Have a safe and enjoyable holiday and best wishes for 2015!

Pancake ice on the River Dee in Scotland

Pancake ice on the River Dee
Photo by Jamie Urquhart, biologist from here

If the Queen of England were in residence at the moment at Balmoral Castle, Scotland, her summer residence, and if she walked downstream a few miles, she'd see the stunning cluster of pancake ice on the River Dee!

How does such ice form? To start with, we probably need to review a phenomenon known as "frazil ice."  Water normally freezes at 273.15 K (32 F), but can be supercooled down to almost 231 K if there are no nuclei for the ice crystals (that is, the water needs to be very pure). Frazil ice forms in turbulent, slightly supercooled water. It consists of small discs of ice 1-4 millimeters in diameter and 1-100 microns in thickness.  It is estimated that sometimes there can be one million ice crystals in a cubic meter of water. As the crystals grow, they will stick to objects in the water and tend to accumulate on the upstream side of objects.  This can cause ice dams and serious flooding.  

Frazil ice in rivers can be a serious problem if there are hydroelectric facilities because it can block turbine intakes, or can freeze open gates. It's also hard on the fish! In the ocean, frazil ice forms around the edges and within open water within ice packs.  Here it has become of concern because of oil and gas development in the Arctic. A review article on this by Sellye Martin can be found in Annual Reviews of Fluid Mechanics, v. 13, pp. 379-397, 1981.)

According to the CNN article referenced in the figure caption, there have been some cold nights in Scotland. They speculate that the disks form at night (and are round because they form in swirling eddies), soften in the daytime so that the rims get pushed up by collisions, and then grow further the next night, etc. Pancake ice is a well understood phenomenon on the oceans.

Atmospheric Rivers and the storms of December

Wind gusts forecast for 1:00 p.m. (tomorrow afternoon)

As I logged into Cliff Mass's blog to do my homework for this post, I saw that he had updated his latest post as follows:

"BIG NEWS UPDATE at 10:15 AM Wednesday:  At 10 AM, Seattle-Tacoma Airport reported 65F, the WARMEST TEMPERATURE EVER OBSERVED AT SEA-TAC FOR THE MONTH OF DECEMBER.  I repeat this is the warmest temperature every reported for any day in December in the entire climatological record.  Amazing.  Undoubtedly true of other Northwest sites as well.

"I ([Cliff] had to laugh today when I saw the front page of  the National Weather Service's Seattle forecast office web site. 
They had FOURTEEN watches, warnings, and advisories. 

"I have never seen so many.   Something out of a disaster movie or reminiscent of the plagues that hit Egypt before the Exodus.   High Winds!  Floods! Small Craft Advisory!  High Surf!  Gales! Storms! Rough Bars!  All that was missing were tornadoes, hurricanes, lice, and darkness.  Oh, I forgot, we have darkness living in Seattle during the winter.

"But it is getting very clear that the Oregon coast is going to be ground zero for a major onslaught of wind.  Hurricane-force gusts. "

All of this is being treated by the popular press as the result of an "atmospheric river," (AR) as if that was a new concept, but it's not! Two MIT researchers, Zhu and Newell, 1998*) first described the phenomenon. They found that most of the water vapor in the global conveyor belt is carried in 4-5 long narrow  water-vapor-rich sections that are only about 400 km wide. A much older term describing California storms is the "Pineapple Express" applies to a subset of atmospheric rivers that have a connection into the tropics near Hawaii. When the AR''s draw in moisture from the tropics, they can be extreme. Here's a link to a previous post that I did on atmospheric rivers. It relates to Japanese fire bombs during WWII.

A plot of the amount of moisture in a vertical
atmospheric column for an AR in 2010
(from Cliff Mass, here)

The AR's are rich in water vapor, and because of the pressure gradients that develop in cyclones/hurricanes, they are associated with strong winds. The winds will force the water vapor up and over topography, leading to condensation of the vapor and precipitation in the form of rain or snow. According to the NOAA site referenced below, 42 AR's impacted California during the winters of 1997-2006, resulting in seven floods along the Russian River watershed northwest of San Francisco, a major "New Year's Day Flood" in 1997 that caused over $1 billion in damages, and contributions to other California storms in the Merced and American Rivers. An AR hit the Pacific Northwest in 2006, producing heavy rainfall, flooding, and debris flows with damage excepting $50 million. You can find a list of NOAA's "notable AR's" here.

Here's a quote from an article by Dettinger and Ingram that illustrates what one of these rivers can do:

"The intense rainstorms sweeping in from the Pacific Ocean began to pound central California on Christmas Eve in 1861 and continued virtually unabated for 43 days. The deluges quickly transformed rivers running down from the Sierra Nevada mountains along the state’s eastern border into raging torrents that swept away entire communities and mining settlements. The rivers and rains poured into the state’s vast Central Valley, turning it into an inland sea 300 miles long and 20 miles wide. Thousands of people died, and one quarter of the state’s estimated 800,000 cattle drowned. Downtown Sacramento was submerged under 10 feet of brown water filled with debris from countless mudslides on the region’s steep slopes. California’s legislature, unable to function, moved to San Francisco until Sacramento dried out—six months later. By then, the state was bankrupt.

A comparable episode today would be incredibly more devastating. The Central Valley is home to more than six million people, 1.4 million of them in Sacramento. The land produces about $20 billion in crops annually, including 70 percent of the world’s almonds—and portions of it have dropped 30 feet in elevation because of extensive groundwater pumping, making those areas even more prone to flooding. Scientists who recently modeled a similarly relentless storm that lasted only 23 days concluded that this smaller visitation would cause $400 billion in property damage and agricultural losses. Thousands of people could die unless preparations and evacuations worked very well indeed."

Finally, on another note that picks up on a few previous posts (http://www.geologyinmotion.com/2014/10/update-on-this-years-el-nino.html;  wondering if we are in an El Nino year, Japan's weather bureau just announced that they find that an El Nino has emerged for the first time in five years, and is likely to continue into the winter. This is the first declaration by a major meteorological bureau of the "much-feared El Nino phenomenon." The pattern emerged between June and August and they signs of it in November as well. An El Nino year leads to drought in some parts of the world, flooding in others. 

It should be an interesting few months!

*Zhu, Y, and R. E. Newell, 1998: A proposed algorithm for moisture fluxes from atmospheric rivers. Mon. Wea. Rev., 126, 725-735, doi:10.1175/1520-0493(1998)126<0725:apafmf>2.0.CO;2.

http://www.esrl.noaa.gov/psd/atmrivers/questions/ for a summary of into

A little known, potentially dangerous, volcanic system at Laguna del Maule, Chile

Maule Lake image
from http://earthobservatory.nasa.gov/IOTD/view.php?id=76827
Note the grey lava flow at the bottom center edge of the Lake

Where in the world is the earth moving up at about 1' per year? Not Yellowstone, but at a relatively little known volcanic field that straddles the crest of the Andes at 36 S latitude.  A recent article by Brad Singer et al. entitled "Dynamics of a large, restless, rhyolitic magma system at Laguna del Maule, Southern Andes, Chile" in GSA Today, v. 24(12) pp. 4-10, 2014 describes this field and it's potential danger. The Lake lies within a 15x25 km caldera. The volcanic complex covers about 300 square kilometers, and contains a cluster of stratovolcanoes, lava domes and cinder cones. The volcanoes sit about 90 km over the subducting slab of the Nazca plate.

The field has 13 cubic kilometers of rhyolite erupted during the past 20,000 years. There have been a dozen crystal-poor, glassy rhyolitic lavas during the Holocene (the past 11,700 years).

In March 2013, the Observatorio Volcanologico de los Andes del Sur (OVDAS) issued a yellow alert, indicating a potential eruption within months to years based on an alarming surface uplift over the last 7 years and swarms of shallow earthquakes.  (In 2010 there was a M8.8 earthquake 230 km to the east.) Early activity in the Pleistocene culminated in "a spectacular concentric ring of 36 separate post-glacial silicic eruptions" between about 25,000-2,000 years ago. The most recent eruptions "were from 24 vents and produced 15 rhyodacite and 21 rhyolite coulees and lava domes." The vents encircle the lake basin. Pumice and ash fall deposits in Argentina may equal these flows in volume.  The only comparable Holocene rhyolite flareup, the authors point out, is along the Mono Craters chain in California.

According to Fournier et al. (2010)*, the rate of surface deformation was negligible from January 2003 to February 2004, but then accelerated between 2004-2007. Feigel et al. (2014)^ have found uplift rates exceeding 280 mm/year (28 cm/year; 11 inches per year). In comparison, this is 2-5 times the greatest rates measured for Yellowstone or Santorini.

Electrical resistivity data suggest a magma body with a hydrothermal system at about 5 km depth, at a location that agrees well with the source of inflation inferred from the geodetic data. 69% of recorded earthquakes between 2011 and 2014 are shallower than 5 km, and most occur under rhyolite vents along the periphery of the uplifting region.

Figure 5 in the referenced paper. Hypothesized
cross section of the Laguana del Maule complex.

The current observations are interpreted in terms of the magmatic mush model of Hildreth (2004) and Hildreth and Wilson (2007), a model that was originally developed to explain the integrated observations of the Long Valley system that erupted 650 cubic kilometers of the Bishop Tuff 767,000 years ago. The magma system is inferred to contain a thin boundary layer of granitoid that is solidified against country rocks.  "Inboard" of this is a rigid "sponge" consisting of crystals with some minor interstitial melt, and inside of this is a crystal rich mush. The mush is maintained in its partial molten state by fluxing of heat and magic magma through the deeper parts of the crustal reservoir. Melt-rch lenses develop near the roof, creating a low-density barrier through which the denser mafic magma cannot rise to the surface. This mush near the top can be tapped to provide the recent/future rhyolitic eruptions.

The proposed setting under the volcanic complex is shown in the figure to the right/above. It includes inferences consistent with the rapid uplift, shallow earthquakes, active intrusion of magic magma at 5 km depth, and normal faulting and geodetic data that record radial extension to form the circumference of vents.

_________________
*Fournier, T.J., et al., Duration, magnitude and frequency of subaerial volcano deformation events: Nw results from Latin America using InSAR and global synthesis, Geochemistry, Geophysics, Geosystems, 11, doi: 10.1029/2009GC002558

^Feigl, K.I., et al., Geophysical Journal International, v. 196, 885-901, doi:10.1093/gji/ggt438

Bardarbunga and SO2 emissions: comparison with Laki 1783

Bardarbunga spewing gas from Nature/News
Arctic-Images/Corbis

"Gas-spewing Icelandic volcano stuns scientists". So reads the headline in Nature/News on October 28. Bardarbunga, about 250 km from Reyjkjavik, has been erupting for over two months (see previous posts on this blog here and here). The reason that scientists were "surprised" is that they had been expecting Bardarbunga to mimic the 2010 Eyjafjallajokull eruption that spewed ash high into the flight paths of airplanes, and instead, they are getting lava flows and gas.

Over a period of about two weeks in August, magma moved underground (in a configuration called a dike by volcanologists) approximately 45 km to the edge of an ice cap. There it began erupting into a barren plane called "Holuhran". Along with the lava, SO2 has been erupting in such quantities that Austria is recording more sulphur in its air than anytime since the 1980's when industrial pollution was still at high levels in Europe.

NASA Earth Observatory image in early September

How much sulfur dioxide is being emitted? Estimates are about 35,000 metric tons (tones) per day, and the Nature/News article uses the comparison that this is about twice the amount spewing from all of Europe's smokestacks. In the town of Hofn, sulfur spikes as high as 21,000 micrograms per cubic meter have been measured, more than 40 times the recommend maximum 10-minute exposure of 500 micrograms per cubic meter, according to the WHO. Hofn lies southeast of Bardarbunga (about 250 km as far as I can estimate) across the entire expanse of Vatnajokull. In early September, people in Norway 800 miles away reported smelling sulfur from the volcano.

The eruption site is remote, winter is setting in making logistics difficult, and the darkness of winter at such high latitudes will limit the amount of data that can be collected. The limited ground observations will be supplemented by satellite observations.

In 1783-1784, a fissure eruption similar to this one, known as the "Skafta fires" or the 1783 Laki eruption, spewed forth about 14 cubic kilometers of lava, nearly 1 cubic kilometer of ash, 8 million tons of hydrogen fluoride, and 120 million tons of sulfur dioxide, producing the "Laki haze" across Europe.  In Iceland, this is known as the "Mist Hardships," killing 20-25% of the population by famine and fluoride poisoning, 80% of the sheep, 50% of the cattle and horses. It is speculated that the eruption weakened the African and Indian monsoons, causing low flow on the nile and a famine in Egypt that killed 1/6 of the population. In Europe, the weather became hot through the summer of 1783, the winter was also severe, and the weather disruptions continued for several years. In North America, the winter of 1784 was miserable, with the Chesapeake freezing over at Annapolus, the Mississippi froze at New Orleans, and there was ice in the Gulf of Mexico. Benjamin Franklin made observations of the fogs in Europe and in North America and speculated that it was due to Hekla in Iceland, not knowing about the Laki eruption.

Assuming that the 120 million tons of SO2 in the 1783 eruption was degassed uniformly over 8 months, the rate averaged about 500,000 tons per day. Ignoring the 10% difference between metric tons (tonnes) and short tons, the Laki degassing was about 15 times as intense as the Bardarbunga. The last event similar to the current eruption began in 1975, the so-called Krafla fires, and lasted until 1975. Freysteinn Sigmundsson, a volcanologist at the University of Iceland and co-leader of the FUTUREVOLC project, suggests that the current eruption could continue for months or years if, as it appears, magma deep in the crust is being tapped.

Update on this year's El Nino

Sea Surface temperature anomalies in the "Nino 3.4 area
of the tropical Pacific. From Cliff Mass site referenced
in the text. An anomaly greater than 0.5 C is required
to forecast an El Nino, and it is not being seen.

A few months ago, I posted that there was uncertainty about the development of a strong El Nino this year.  The verdict seems to be in, and rather than repeat a good analysis, I refer you to my favorite meteorologist, Cliff Mass. Here's a link to his "wimpy El Nino" conclusion! For us in the Pacific Northwest, it means that predictions for the winter basically can't be done, unless the El Nino suddenly strengthens.

Super Typhoon Vongfong headed for Okinawa

Stay safe, dear friends in Okinawa and Japan!

The largest typhoon of the calendar year is heading toward Okinawa. It is the fifth super typhoon of the year (150 km sustained winds or higher). It is the strongest storm since Typhoon Haiyan, which killed over 5,000 people in the Phillipines in November, 2013. It is following on the heels of Thyphoon Fanphone which struck near Tokyo just a few days ago.

Forecast from The Weather Channel

According to The Weather Channel, it intensified rapidly overnight Monday. As of 11:00 a.m. EDT on Wednesday in the U.S.), the eye of the hurricane was just under 600 miles south-southeast of the major Kadena Air Base on Okinawa (see graphic), and it was moving northwest at 8 mph. According to a report in Stars and Stripes:

7:30 a.m. Thursday, Oct. 9, Japan time: Not good, campers. Joint Typhoon Warning Center’s latest forecast track depicts a slightly closer turn by Vongfong to Okinawa late Saturday into Sunday. Closest point of approach now projected at 62 miles east-northeast at about 10 p.m. Saturday.

That changes the wind forecast timeline for Okinawa given Vongfong’s latest forecast proximity to Okinawa. Here’s the latest from Kadena Air Base’s 18th Wing Weather Flight:

• 29-mph crosswinds at Kadena, from 3 p.m. Friday.
• Sustained 40-mph winds, from 2 a.m. Saturday.
• Sustained 58-mph winds, from 11 a.m. Saturday.
• Maximum 63-mph winds and 74-mph gusts at Kadena, maximum 81-mph sustained winds and 104-mph gusts over northeastern Okinawa at 11 p.m. Saturday.
• Winds diminishing below 58 mph sustained, from 6 a.m. Sunday.
• Winds diminishing below 40 mph sustained, from 11 a.m. Sunday.
• 29-mph crosswinds no longer occurring at Kadena, from 11 a.m. Tuesday.

All of this could change, since there’s a large disparity among dynamic model guidance. JTWC forecast tracks tend to fall toward center of model consensus. We’ll see how things go in the next couple of days. PST will keep this under finger.

It is likely to to hit Honshu on Monday into Tuesday as a Category 1 tropical storm. Some areas that will be hit experienced up to 10" of rain from Phanfone, so the danger of flash flooding and mudslides along the eastern coast of Japan is high, with some areas getting an estimated 8-12" of rain.

The conditions that contributed to the rapid intensification were very low vertical wind shear, high outflow winds spreading away from the center and thus encouraging upward motion of air and thunderstorms, and warm western Pacific water. The estimated central pressure is about 900 millibars.

Ontake, Japan, erupts

Ontake erupts. Photo by andreijejune as cited above.
The eruption started around 11:53 a.m. Saturday, local
time (in spite of the setting in the caption above)

UPDATE SUNDAY: The Japan Times is reporting that 31 people were found unconscious near the peak of Ontake, and that four have been pronounced dead. The BBC is reporting that there were a total of 45 missing climbers. Japanese officials only announce deaths after a formal examination by a doctor. I extend condolences to the families of the victims and missing.

A few hours ago (Saturday), Mount Ontake 155 miles west of Tokyo, erupted, sending a steamy ash plume high into the sky. It last erupted in 2007. News is conflicting about the casualties, but at least one person has been killed,  thirty people have been injured and the Japanese are organizing to rescue an unknown number (reports vary between 41 and 200?) people who were climbing on the mountain. As much as 20" of ash has been reported on the ground near the summit, and Japanese authorities are issuing an alert to stay at least 4 miles away from the summit. The alert level is "3" meaning "do not approach the volcano." Ash is reported to have gone 3 kilometers down the mountain in a pyroclastic flow. There are a number of YouTube videos showing the eruption through cameras held by hikers. Here's one.

From the Kinja Space site cited
in the text and the twitter
user identified above.

Ontake is the second highest volcano in Japan, at 3,067 meters, second to Mount Fuji. There is a nice description of the tectonic setting of Ontake, as well as a collection of eyewitness accounts, at Kinja Space, authored by Mika McKinnon, from which I take much of the following discussion. The author of this blog nicely states that because of geochemical differences in the magmas, volcanoes over oceanic tectonic plates typically have a relatively low abundance of silica (SiO2) and are fairly fluid allowing their gases to escape rather gently (think Iceland, Hawaii). When the eruptions do turn explosive, it is usually because the magma has interacted with groundwater or ice.  Volcanoes that are rich in silica are viscous and gases don't escape easily, leading to conditions that produce explosive eruptions. Such volcanoes usually are found where oceanic and continental plates intersect. The Pacific Ring of fire that stretches up from South America, through western North America and around to Japan is such a setting and eruptions here can be very dangerous. Eruptions of these volcanoes produce flying rocks, volcanic bombs, and hot pyroclastic flows. The movies of the survivors are lucky to be alive.

Ontake had a minor eruption involving water (phreatic) in 2007, but the last major eruption stretched from October 1979-April 1980. In spite of claims that it had erupted in 1892 and 774 AD, detailed examination of the records suggest that this is not true and that it had not erupted prior to the 1979-1980 sequence in recorded history, which is a long time in Japan. Local volcanologists/seismologists Koshun Yamaoka and Shigeo Aramaki are suggesting that the billowing white clouds seen in the eyewitness photos suggest that this is a phreatic eruption.  The possibility that phreatic eruptions are signaling heating of groundwater by rising magma leaves open the scenario of a major magmatic eruption like that of Mount St. Helens that began about 4 hours after the 1980 March-April lateral blast.

Mayon and Bardarbunga volcanoes.

Mayon volcano, copyright Tom Tam shot from
Lingnon hill in Daraga Town near the volcano and his home

Mayon, a stratovolcano of nearly perfect symmetry, in the Philippines is again active. It is one of the most active volcanoes in the world. It has erupted 49 times in the past 400 years.  Coincidentally, the most destructive eruption was in 1814, a year before Mount Tambora erupted, with the emission of ash that led to the "Year without a summer" in 1816.  New reports today are that more than10,000 people from around the volcano are being evacuated.

The volcanic activity is being actively reported on Wiki here, and here is the link to the Philippine Institute of Volcanology and Seismology, PHILVOLCS. The monitoring network has detected 39 rockfall events that are "ascribed to incipient breaching of the growing summit lava dome." Continuing seismicity indicates either magma intrusion or volcanic gas activity, and there is sufficient magma in the summit crater to cause a red glow. PHILVOCS has raised the alert level to Level 3, stating that a hazardous eruption is "possible within weeks." A Permanent Danger Zone extends out to a 6 km radius, and an Extended Danger Zone to 7 km. These are being evacuated because of danger of rockfalls, landslides, and lava/ash/mud flows. (Level 3 is the third highest level of alert, following "eruption" and "imminent eruption.")

Bardarbunga in Iceland continues to be active seismically and as of a flyover of the Holuhraun fissure on Sept. 12, about 200 cu meters of magma per second are erupting. Lava is flowing nearly 20 km from the vent.

Major solar storm, alert for a CME, coronal mass ejection

Sunspot region 2158, the source of a solar flare today
From Spaceweather.com here

UPDATE 2: From space watch.com:

STORM WARNING (UPDATED): Among space weather forecasters, confidence is building that Earth's magnetic field will receive a double-blow from a pair of CMEs on Sept. 12th. The two storm clouds were propelled in our direction by explosions in the magnetic canopy of sunspot AR2158 on Sept. 9th and 10th, respectively. Strong geomagnetic storms are possible on Sept. 12th and 13th as a result of the consecutive impacts. Sky watchers, even those at mid-latitudes, should be alert for auroras in the nights ahead.

UPDATE 1: I have posted a number of relevant items over the past few years on solar storm activity: 

• General background about space weather, CME's and solar flare
• One of my most popular posts, a 2010 one titled "Solar activity (and Newt Gingrich)"
• An X5-class solar flare in March, 2012
• In January 2012, the biggest flare since 2005 and here.
• An aurora viewed as far south as the midwest
• And, another flare/CME on February 15, 2011___________________

While our daily earth-weather is filled with heat waves still hitting us as summer fades into autumn, something 'out there' is ready to hammer us! Sunspot region 2158 spat forth a "long duration X1.66 (R3-strong radio blackout) solar flare today. It peaked at 17:45 UTC on Sept. 11  (11:45 a.m. PST on Sept. 10).

This sunspot region has been active for a few months. On September 1 it was the source of a flare, but on the backside of the sun. However, this region is now directly facing the earth. Solar scientists are awaiting data, but they think that it's likely that a Coronal Mass Ejection (CME) of particles will follow.  Information is updated regularly at NOAA's Space Weather Prediction Center here.

Why should we care? A CME has the potential to disrupt electronics that we depend on, whether in space for communications or on earth in health care facilities, computer centers, or communications facilities. A CME can also pose biological risk to astronauts and to passengers and crew in high-altitudes--especially if they are flying cross-polar routes where the particles preferentially come into the earth along magnetic field lines.

According to Mike Wall, a senior writer at Space.com,  the sun "unleashed an X-class solar flare--the most powerful type" today, and it also fired off another intense flare yesterday. Fortunately, NASA in these times of diminishing funding, still has the Solar Dynamics Observatory spacecraft which recorded the event. The flare was an X1.6 storm, and space.com says that it "poses no danger to anyone on Earth or the astronauts living aboard the International Space Station." However, radio communications on earth, the side facing the sun could experience radio communications lasting 'more than an hour.' However, if the eruption is accompanied by a CME, in 2-3 days, there might be significant geomagnetic storms that can disrupt GPS signals, power grids, and  communications.

We are near the peak phase of the Sun's 11-year cycle (Solar Cycle 24), but this phase is the weakest in about 100 years....and that's a whole other discussion!

Meteorite impact in Nicargua: brief report

The crater from the meteorite impact
From this reference

A fragment of the meteorite passing close to earth has made a crater in Nicaragua. I'll post more when I've got some reliable information.

http://www.cnn.com/2014/09/08/tech/innovation/nicaragua-meteorite/index.html?hpt=hp_t2

A fissure near Bardarbunga volcano, Iceland, has erupted

Location of the fissure eruption at Bardarbunga
from www.bbc.com here

On Sunday, a "curtain of fire" developed along a fissure near Bardarbunga, causing a brief alert and a banning of planes flying within 6,000 feet of the volcano. The eruption was described as "calm but continuous."

A detailed chronology of the current activity is being maintained on Wiki. Seismic activity has been continuous, with lava erupting on August 29th in the Holuhraun lava field. The active fissure was about 600 m long, and the entire eruption appears to have been only about 4 hours long. Seismicity quoted down during the eruption, but then returned. On August 30th it appeared that the dyke stopped migrating north, but seismicity continued. Another eruption began at 4:00 a.m. on August 31st, producing a lava flow about 1 km wide, 3 km long, and several meters thick. The flow rate was estimated at 1000 cubic meters/second. Seismic activity is continuing. Updates are posted continuously on the Icelandic Met Office webpage. They've posted the adjacent interesting map showing road closures north of Vatnajokull as a result of the current activity and potential flooding (the hashed area north of the big ice cap).

The mysterious "sailing stones" of Death Valley

Credits as above. Picture grabbed from ScienceDaily.com.

How can a rock weight several hundred pounds move hundreds of meters across a "dry lake"?  And, why do they move in tandem? One of the early pioneers in solving this mystery was Robert Sharp* of Caltech, and many others have speculated about this problem. Sharp monitored stones over a period of seven years stretching from 1968-1974, and concluded that movement was related to wet stormy weather. Sharp and Carey documented a greatest cumulative movement of 262 m, and "greatest single-episode movement, of 201 m. These were of a small 250 g stone, but other moved stones weighed as much as 25 kg. They concluded that movement "most likely occurs within one to several days after playa wetting, and velocities on the order of 0.5 to 1 m/sec are inferred from track characteristics." Sharp and Carey reported eyewitness accounts of ice sheets containing frozen stones being propelled by wind on other southern California playas, and inferred that the stone tracks at Racetrack were made in this way. However, there were observations that led them to conclude that the stones could not move within extensive ice sheets: they moved out of an encirclement of iron stakes that Sharp and Carey had placed and their spacing changed during movement.

Stationary rocks (blue arrows) and rock moving from left to right (red arrow)

The team used quarried rocks,
one shown here with its
GPS unit

Now, the process has actually been observed by a team led by Richard Norris of Scripps Institute of Oceanography.** In what one of the co-authors, Ralph Lorenz, described as potentially the most boring experiment ever, the scientists outfitted 15 rocks with motion-activated GPS sensors and placed them on the playa to await movement. Only two years into the project, not only did the rocks move, but Norris and Norris were there at the time. When they arrived in December 2013, there seven centimeters (3") of water on the playa, and they concluded that not only must water be present, but it must be deep enough to form "floating ice" during cold winter nights, but shallow enough to leave at least part of the rocks exposed. Panes of ice form during the night, and on sunny days the ice can begin to melt and break up into panels that float across the water if there is wind. These panels actually push the rocks in front of them. The wind speeds were about 3-5 meters/second (10 mph), and the ice that moved was about 1/4" thick.  These speeds are much lower than inferred from track characteristics by Sharp and Carey. The rocks moved at 2-6 meters a minute, and moved for a few seconds to 16 minutes. The rock trails formed under the ice, and became visible only when the water underlying the ice is blown away by winds.

Floating ice moves around the playa under the influence of winds. When it encounters rocks, it may pile up on the upstream side, increasing the effective cross-sectional area of the rocks to both upstream ice and water and thus facilitating movement. On the other hand, sometimes the ice fragments upon encountering a rock. Norris and Norris suspect that this phenomenon might explain the Sharp and Carey observation of the corral behavior: the rock that didn't move out of the corral was just downstream of a stake that may have shattered the ice. Stones with low profiles might be submerged beneath the ice, some rocks may be too big for the available forces under some wind conditions, and others may not totally or partially encounter ice.

But, the researchers concluded, the mystery may not be completely solved: they didn't get to see the really big ones move.

The authors also point out that the sliding rocks are not unique to Racetrack Playa or even the U.S. Ice-driven rock trails are observed on the bottom of Great Slave Lake in northern Canada and on the shores of the Baltic Sea. The mechanism may apply to rock trails on dry lake surfaces in Spain and South Africa where the lakes are at high elevation and exposed to cold winters.

*Robert P. Sharp and Dwight L. Carey, Sliding stones, Racetrack Playa, California, GSA Bulletin, 87(12), 1704-1717.

**Richard D. Norris, James M. Norris, Ralph D. Lorenz, Jib Ray, Brian Jackson, Sliding rocks on Racetrack Playa, Death Valley National Park: First observation of rocks in motion. PloS ONE, 2014; 9(8) e105948 DOI:10.1371/journal.pone.0105948 link to article is here

South Napa Earthquake today, M 6.0-6.1--geologic context

Building destroyed in Napa. Photo by Justin Sullivan,
Getty Images as published on www.sfgate.com here

UPDATE AUGUST 25: Greg Braswell, as noted in his comment, has published images of the damage and an iso-damage map. They can be found at:

https://plus.google.com/photos/111007793583080982677/albums/6051216644873549681

and

https://mapsengine.google.com/map/edit?mid=zv4bNVwln6qk.kOPvmSymk_d8

Headlines this morning announced that a M6.0 (or 6.1, conflicting reports) earthquake at 3:20 a.m. awoke people around the area of Napa, California, north of San Francisco.  Dozens of people are injured, four homes in a mobile park burned, and damage to buildings in downtown Napa appears extensive. The quake is the largest in the Bay Area since the 1989 Loma Prieta earthquake.

        Here's a bit of context that I found in an on-line technical report authored by John R. Wesling and Kathryn L. Hanson, 2008 (reference at the end of this post). Here is also a link to the USGS earthquake event page.

Map of the five sections of the fault defined by Wesling
and Hanson (Figure 3 from the cited report)

        Napa Valley is a large valley that trends to the northwest. It extends from Calistoga to the southern part of Napa and includes much of the core of the city. The valley is filled with Quaternary alluvial and fluvial deposits from the Napa River system, and earthquake damage in Napa can be especially severe during earthquakes because of shaking of these deposits. The West Napa Fault and its branches were first mapped by Weaver (1949), and subsequent work extended from the 1970's into the 1990's (references in the article cited). This early work reported that the fault and its branches extend 30-35 km along the western margin of the Valley; the Wesling and Hanson report suggests that the fault is 57 km long, extending from Carquinez Strait northwest toward St. Helena. The orientation and geomorphic expression are consistent with the West Napa fault being dominantly a right-lateral slip fault, with some compression that allows development of the nearby mountain ranges. The West Napa fault is one of a series of fairly short faults that include the Franklin and Sothampton faults. These faults lie between the Hayward-Rodgers Creek Fault zone (west) and the Calavaras-Concord-Green Valley fault zone (east).

          Wesling and Hanson divided the fault into five reaches based on geomorphic expression, terrain traversed, and availability and quality of data. These branches are: St. Helena-Dry Creek; Yountville-North Napa; North Napa-Napa River; Napa River-American Canyon; and American Canyon-Carquinez Strait. The USGS is reporting that the earthquake struck 3 miles northwest of American Canyon, and placed the epicenter between 6 miles southwest of Napa, toward Vallejo (see adjacent map). According to the map above, this would place the epicenter on the Napa-River-American Canyon fault toward the northern end or, possibly, the southern end of the North Napa-Napa River branch, depending on where the reference point within Napa city is located.

            No historical earthquakes larger than M6.0 have been associated with the West Napa fault, although the M5.0 Mount Veeder earthquake ("Yountville earthquake") in 2000 may have been linked to it. This earlier earthquake was centered about 5 km west of the West Napa fault, and caused considerable damage in Napa.


Reference: "Mapping of the West Napa Fault Zone for Input into the Northern California Quaternary Fault Database," by John R. Wesling and Kathryn L. Hanson, 2008.

Bardarbunga volcano, Iceland, rumbling!

UPDATE: August 23, 2014

__________________________________________

Chaotic ice in Vatnajokull over Bardarbunga
Image from the Smithsonian site here

UPDATE: UPDATE: August 23, 2014. Here is a link to the Icelandic Met Office Bardarbunga information. New information is constantly added at the top of the article.  At 14:10 (Icelandic time), a small eruption of lava was detected under the Dyngjujokull glacier (east of Bardarbunga). Data from radar and web-cams (see this link, for example), have shown no signs of surface activity breaking through the 150-400 meter thick ice. However, the aviation code has been changed from orange to red, though no Icelandic airports have yet been closed. The Icelandic Met office estimates that it could be up to 20 hours before lava breaks through the ice, if it even does. The eruption could remain subglacial. Earthquake activity has continued since August 16. Flooding remains a possibility, with the bridge shown in the picture potentially at risk on the circum-Iceland road.

Earlier in the day, scientists reported that seismic activity indicated that a dyke was propagation as much as 5 miles to the north. On August 21, the dyke was reported to be 25 km long at a depth of 5-10 km. GPS data show that magma is moving.


ORIGINAL POST:

Earlier in the day, scientists reported that seismic activity indicated that a dyke was propagation as much as 5 miles to the north. On August 21, the dyke was reported to be 25 km long at a depth of 5-10 km. GPS data show that magma is moving.


Headlines are starting to appear about seismic activity under Bardarbunga volcano, which lies under Vatnajokull in Iceland, but with frustratingly little information as they hark back on the sensationalism of airplane flights cancelled when Eyjafjallajokull erupted a few years ago. More than 300 people in the region have been evacuated as a precaution. Flooding is a possibility.

 Rather than paraphrasing, here are extracts from the Smithsonian volcano report:

13 August-19 August 2014 

During 13-19 August the Icelandic Met Office reported increased seismic activity at Bárdarbunga volcano. On 16 August more than 200 earthquakes were reported under the NW Vatnajökull ice cap, and GPS stations have shown an increasing signal upward and away from the volcano since early June 2014. On 16 August the Aviation Color code was increased to Yellow. On 18 August the Icelandic Met Office reported an earthquake swarm to the E and another to the N of Bárdarbunga. A M4 earthquake was recorded that was the strongest in the region since 1996. By 18 August there had been 2,600 earthquakes detected at the volcano; earthquake locations from N and E swarms had been migrating NE, but in the evening activity of the N swarm had decreased significantly. That same day the Aviation Color code was raised to Orange. 

Credit: Reuters, as published in bbc.com here

The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.

The Veidivötn fissure system, which extends 100 km SW from Bárdarbunga volcano, has been the source of major eruptions during the Holocene. A large, dominantly explosive eruption at about 870 AD from the Vatnaöldur crater row, which extends diagonally across the center of the photo, deposited tephra over much of southern Iceland. The Vatnaöldur eruption originated from a 42-km-long fissure and produced 3.3 cu km of tephra at the time of the settlement of Iceland, forming the the Landnam (Settlement) tephra layer. 

The subglacial Loki-Fögrufjöll volcanic system...glacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge, seen here, extends to the SW. 

Weather extremes, atmospheric rivers and Japanese fire bombs

A shot-down Japanese fire balloon
reinflated by the US
File uploaded by Bkwillwm to
Wikipedia, public domain

     In my book, "The Dynamics of Disaster" (Norton Press, 2013), I discuss the big "rivers in the sky"--our jet streams.  These atmospheric rivers were discovered in the 1920s by Wasaburo Ooishi, a Japanese meteorologist studying the dynamics of the atmosphere near Mount Fuji. To quote my book: The Japanese "were able to turn their knowledge of the jet streams to their advantage during the war by launching balloon attacks on the US, sending 9,000 "fire balloons" aloft to travel thousands of miles east. Some 300 made it to US soil, and six people died when a family approached one and it exploded. (These were the only known deaths by enemy action on continental US soil during World War II.)"
        In a new study by Dim Coumou and a team from Potsdam Institute for Climate Impact Research published August 11 in the Proceedings of the U.S. National Academy of Sciences (ref. below), Coumou points out that the large number of very high-impact extreme weather events over the past decades has seemed out of proportion to the rate of warming of the atmosphere caused by increased CO2. The authors rely on, and quote, an earlier paper in PNAS by Petoukhov, et al. (of the same institute) reporting the same thing: the frequency of these extreme events over the past decade is such that it is unlikely to be just a "stochastic mechanism of extremes."
        And, here's where the Japanese discovery of the jet stream becomes relevant, because it's in the jet stream that the changing flow patterns are driving the weather extremes.

From the cited PNAS article. Shows the increase in so-called "boreal summer weather extremes."

        Again, quoting from my book: "Flowing at the top of the troposphere, the jets have variable elevations between 12,000 and 80,000 feet...[They] can be several hundred miles wide and 1-2 miles deep, and they can flow at speeds of up to 400 mph. Jet stream winds generally flow from west to east, but they have a loopy structure and flow in various directions, even "backward," from east to west, in some segments. The looniness, known as a Rossby wave, has a wavelength of about 1,800-2,400 miles and arises primarily because the Coriolis effect has different strengths at different latitudes. The jets can split apart, re-join, reverse, or simply stop.When the Rossby waves move to the north, they suck warm air northward, e.g., from the tropics into Europe, Russia, or the US. They do the reverse when they move south, transporting cold air from the Arctic to the south.  " I then go on to explain how the position of the jet stream and the Rossby waves influenced the position of Hurricane Sandy in October 2012.
       Now back to the research of Coumou and his team: According to the theory advanced in the article (based on analysis of meteorological conditions from 1979 to 2012), there are resonances in the atmosphere that trap the Rossby waves into certain configurations for long periods of time. Thus, a heat wave that would not be dangerous if it were a few days long, becomes extreme when its duration increases. (The paper is limited to analysis of the Northern Hemisphere.)
     The speed at which a wave travels along the jet stream (the "phase speed")  is, in one approximation, directly proportional to the mean zonal wind speed. To first order, synoptic waves with a wave number (k) equal to 6-8 travel at this speed. The zonal mean wind speed changes with season, being less in the summer. Because the zonal mean wind speed is lower in the summertime, the phase speed is also lower because of this direct proportionality. In fact, in the "boreal summer"--July, August--the phase speed can be close to zero (the waves are quasi-stationary, especially for wave number 6) or even negative (that is, the waves would travel to the west instead of the east). This weakening of the zonal wind speed and, hence, the wave speed is one mechanism explored. Free-traveling waves are simply slowed down or stopped. If the waves are stationary, then the troughs and ridges of the Rossby waves are stationary, setting in the northerly or southerly flow of air for long periods.
        The second mechanism is  the amplification of quasi-stationary waves by resonance between free and forced waves in the midlatitudes. Looking at the Petoukhov et al paper, the quasi resonance hypothesis is as follows. (1) Generally, the large-scale atmospheric circulation at mid latitudes is characterized by traveling Rossby waves with zonal wave numbers (k) equal to or greater than 6 propagating in the longitudinal direction at a phase speed of c~6-12 m/s as discussed in the paragraph above. (2) The circulation is also characterized by quasi stationary planetary-scale Rossby waves with c~0, frequency w~0, and various zonal wave numbers m that develop in response to orographic obstacles or weather sources and sinks, that is, to "conditions in the atmosphere that differ from place to place on the earth. Their hypothesis is that during the extreme summer events, persistent wave structures with high amplitudes evolved and made an unusually large contributions that the usually weak midlatitude response to the thermal and orographic sinks was strongly magnified at wave numbers 6,7 and 8.
     They assert that the apparent cluster of resonance events observed in their data set (see their figure reproduced above) is due to an increased wave 7 and 8 resonances, and that furthermore, these resonances high in the atmosphere are coupled to persistent weather patterns at the surface, and thus the extreme weather events. The changes observed are statistically significant at the 95% confidence level.
        The theory and data (from 1979-2012) suggest that because of warming in the Arctic, temperature differences between the Arctic and tropics are decreasing. Temperature differences drive the atmospheric circulation patterns, and changes in these differences (the temperature "gradients") are causing the atmospheric circulation patterns to change. Although much more detailed work and analyses needs to be done, their tentative projection (Figure 7) of conditions a century away shows t"similarities with the recently observed anomalies). According to RCP8.5 climate model (one in which we don't curb our CI2 emissions very much), the July-August thermal gradients will increase northward of 50N and decrease southward of 50N, leading to strengthening of the sub polar jet and weakening of the subtropical jet.


**I have used the report in ScienceDaily.com for parts of this post: http://www.sciencedaily.com/releases/2014/08/140811170106.htm

The abstract for the Coumou PNAS article is here and the full text is here.

The PNAS Petoukhov et al. article referenced is here.

Methane outbursts due to melting permafrost in Siberia: the Yamal crater

Image from the Washington Post here

Update: Of interest may be Alan Weisman's August 12, 2014 article "Why the Earth is farting." Also, see reader comment.

Several months ago, a photo of a crater discovered by a helicopter crew  went viral. It is located in the Yamal Peninsula in Siberia, a desolate spit of land. The crater was variously reported to be 100- 200 feet in diameter. In the July 31 issue of Nature, highlighted in the Washington Post article referenced in the adjacent figure caption, the discovery of two nearby craters is reported in the Washington Post article. The article contains an excellent video taken from a helicopter showing the crater walls actively crumbling. A camera has been lowered to 50 m, and it showed a pool of water at a depth of 70 meters, so the crater extends below 70 m.

Image from Washington Post here

Russian researcher Andrei Plekhanov led an expedition to the crater. He found that near the bottom of the crater (at approximately 50 m depth) air contained concentrations of methane up to 9.6%. That is to be compared to the normal concentration of methane in air--0.000179%. They believe that the abnormally hot summers in Yamai in 2012 and 2013 caused permafrost to thaw. Under the permafrost, usually at depths of 100 meters, methane clathrates are stable. Over the past 20 years, permafrost at a depth of 20 meters has warmed by about 2 C according to the article, quoting Hans-Wolfgang Hubberten of the Alfred Wegener Institute in Potsdam, Germany. Hubberten speculates that a thick layer of ice overlying the clathrates allowed gas pressure to increase until it was great enough to blow out in an explosive burst, forming the crater with rubbly ejecta strewn around it.
     The development of more craters could pose a danger to villages of local reindeer herders, and the craters are only 30 km from a large gas field, the Bovanenkovskoye gas field. A blowout in the gas field cold be very dangerous.

August 2 Major Landslide in Nepal blocks only route out to the North

Image of the landslide from Ekantipur. This appears to be
a view on the upstream side, with the water from the impounded
river flowing to the right and encroaching on the toe of the slide.
Image from Dave Petley's blog post of August 2, 2014.On

On the night of August 1-2, a large landslide occurred along the Sunkoshi River in northern Nepal, damming the river and creating an urgent crisis. I'm not going to follow this event because Dave Petley's landslide blog will be providing excellent coverage. It is the peak of the monsoon season and so the impounded lake behind the landslide is likely growing fast and, Dave believes, may already be overtopping the dam. It also appears that the dam is in fine-grained materials and so the likelyhood of a breach is high. The valley downstream is heavily populated (evacuation has apparently already begun) and the main road from Nepal into China is blocked. The highway, however, does provide a route to bring in heavy machinery and crews to work on excavating a channel through the slide.

Los Angeles geyser on Sunset Boulevard!

Back in the 1970's I used to run on the UCLA track near Sunset Boulevard. Two days ago, a 93-year-old water pipe and a 58-year-old pipe broke under Sunset Boulevard near the track, sending a pulsating geyser of water high into the air.  You can view a video of it here (the video symbol in the center of the photo doesn't work because it's just a frame grabbed from the CNN video).

The track was flooded, as well as newly rennovated ($136 million)Pauley Pavilion, the home of UCLA basketball named in honor of the famous coach of winning teams back in the 1970's. At its peak, the broken pipes were sending 35,000 gallons of water per minute onto the streets, with estimates of 20 million gallons released before the flood was brought under control. Maybe the tartan track will survive, the basketball court is questionable. Firefighters had to rescue some people trapped in a parking structure

Flooded track and athletic field at UCLA

If you watch the video, you'll see that the jet is strongly pulsating. This is likely due to an effect known as a "water hammer." The pipeline was a high pressure line, and these lines are subject to very destructive forces due to the water hammer effect (sometimes called a hydraulic shock). These are pressure surges that arise when the water changes direction or momentum.  In the news, you'll see reports that the pipeline had to be shut down gradually--that's because they had to minimize the potential for water hammers. If a pipe is shut off suddenly at the downstream end (where the vent is on Sunset Boulevard), the mass of water upstream is still moving and therefore can build up high pressure.  Such shocks can cause further breakage in the pipelines. (This is common in noisy old water/steam heaters in buildings.)

Photo of Pauley Pavillion
basketball court by Jason McIntyre

I found an interesting set of numbers on Wiki about this effect: "In hydroelectric generating stations, the water travelling along the tunnel or pipeline may be prevented from entering a turbine by closing a valve. However, if, for example, there is 14 km of tunnel of 7.7 m diameter, full of water travelling at 3.75 m/s,^[3] that represents approximately 8000 Megajoules of kinetic energy that must be arrested. This arresting is frequently achieved by a surge shaft^[4] open at the top, into which the water flows; as the water rises up the shaft, its kinetic energy is converted into potential energy, which decelerates the water in the tunnel."

See the Wiki article for more on water hammers.