|Jim Westphal (1930-2004)|
Thursday, June 25, 2015
Posted by Susan W. Kieffer at 6:51 PM
Wednesday, June 10, 2015
|Scenary of the Wind River area illustrating that the|
surface is covered with sedimentary rocks and
supporting the observation that there is no
active volcanism within about 200 km. From the BBC
article by Matt Walker cited in the text.
The (very mathematical) analysis in this paper constrains the depth of the earthquake to 75 km (plus or minus 8 km), and makes it the second deepest earthquake now identified under a stable continental region. The depth of the Moho in this area is well constrained to be between 42-50 km, so the earthquake occurred well within the mantle, probably >20 km below the base of the crust. The only two other comparable earthquakes that the authors know of are the 1979 Randolphe, Utah, quake at 90 km, and the 2000 Arafura Sea earthquake at 61 km.
What caused this earthquake? The authors mention the possibility that the quake may result from the migration of fluids within the mantle. Such activity is known to cause microseismic activity at great depths in volcanic regions. However, the Wind River range is more than 200 km from the nearest volcanic region, the hot spot of Yellowstone. They also argue that since the Wind River earthquake ruptured an area of about 1,000,000 square meters, this area is much larger than would be expected from fluid-related origin. They cannot rule out this possibility, but prefer an explanation that the earthquake resulted from brittle fracture due to tectonically-derived stresses.
Posted by Susan W. Kieffer at 12:15 PM
Sunday, May 24, 2015
|The jet stream patterns that have set up the current|
wet situation in Texas. From Weather.com here
on May 24.
Lake Texoma is the 12th largest US Army Corps of Engineers lake, behind the Denison Dam on the Red River. It spans both Bryan County, Oklahoma, and Grayson County, Texas at the confluence of the Red and Washita Rivers. The dam site is 5 miles northwest of Denison, Texas. It is a popular lake, attracting about 6 million visitors per year. Water is pouring over the
|Lake Texoma Spillway the morning of Sunday,|
May 24. From TKKToday here. This is an excellent
site to see current and forecasted conditions as well
as helicopter footage of the flooding.
|U.S. Severe weather map as of 12:26 a.m. GMT (7:26 p.m.|
CDT) on May 25 from www.wunderground.com here
As the severe weather map shows, much of the central U.S. is experiencing severe weather in the form of flood warnings and watches, tornado warnings (red), and high wind advisories (blue and pale green near Chicago).
Saturday, April 25, 2015
|Location of earthquake and initial aftershocks|
Map added on 4/26 at bottom showing avalanche problems on Mount Everest.
A strong earthquake occurred in Nepal about 14 hours ago, and as I write this the death toll from the earthquake has risen to 1,457, with more deaths expected. The people face a cold night without shelter, water or electricity in many regions. The world's thoughts are focused on the people of Nepal with hopes that rescue efforts proceed smoothly an rapidly.
Max Wyss, Switzerland, runs a research program WAPMERR, in which he combines geographic data with seismic models to predict the injured and dead, with results sent to authorities and emergency people to aid in the planning of rescue and recovery (Note: you can subscribe to his service on the home page of WAPMERR). Unfortunately, his estimates are for 2000-10,000 fatalities, and 20,000-70,000 injuries. (Wyss's estimates have been updated to the numbers that I cite here just in the time it has taken to write this post, so check back with his site if you want updated information.)
According to the USGS, large earthquakes in this region have been relatively rare with only four events of M6 or larger known to have occurred within 250 km of this earthquake site. Two of these were a M6.9 earthquake in 1988, that caused about 1500 casualties and a M8.0 event in 1934 at roughly the same location of this 1988 event that severely damaged Katmandu and caused around 10,600 casualties.
|Image from Dave's Landslide Blog showing the|
location of the earthquake according to USGS model
Image from Blog as cited in the text
The Indian and Eurasian plates are converging at a rate of 45 mm/year, one of the fastest rates on the planet. This motion drives the uplift of the Himalayas. India is thrust under Eurasia, and the motion between the two plates makes this one of the seismically most hazardous regions in the world. The surface expression of the fault (along the red line in the figure below) in the vicinity of Nepal is marked by the east-west trending Himalaya Front in the north of India and Nepal sits within this belt. To the north is the high Plateau of Tibet. An excellent detailed summary of the regional tectonic setting is available on the USGS events page reporting the current earthquake found here.
|The tectonic boundary between the Indian plate (bottom)|
and Eurasian plate (top) with the red line showing
the surface location of the collision of these
two plates. USGS map as published today in USAToday.com
|The situation on Mount Everest as|
shown in NYTimes.com
News is trickling in that devastating avalanches have killed approximately 20 people on Mount Everest. Sadly, the best time to climb Mount Everest from a weather perspective is now, April and May. Sadly, on April 18, 2014, thirteen people were killed in an avalanche, at a site well known for its danger. There is a dangerous ice fall, known as the Khumbu Icefall, where seracs (unstable blocks of ice separated by cracks in an ice field) loom large over the route. Climbers usually try to pass quickly through here in the early morning before rising day temperatures amplify the hazard. According to Wiki, citing Russell Brice who runs a guide company called Himalayan Experience, ice falling from the serac narrowly missed climbers in 2012, and according to another mountaineer/writer, Jon Krakauer, the 2014 avalanche was triggered when a large block of ice broke off from the bulge. The Khumbu Icefall and the location of the 2014 avalanche are shown on the adjacent figure. It will be very interesting to see if the present large avalanche originated at the same site, but travelled much further all the way down the ice fall to cause so much damage in the Base Camp.
Remember that Nepal is landlocked. Tom Robinson of the University of Canterbury has done a preliminary analysis of the roads likely to be affected by landslides; that analysis is available on Dave's Landslide Blog here. The rescue situation w is dreadfully complicated with the airport closed and most access roads damaged by landslides. (Correction: The airport is open and India and China are flying in relief.) The monsoons are less than two months away, and since it is likely that many rivers are blocked by landslides, air and satellite photography of the landslide settings is essential to analyze future flooding due to blocked rivers.
Posted by Susan W. Kieffer at 1:31 PM
Saturday, April 4, 2015
|Dr. Greg Forbes of the Weather Channel|
reviewing large tornado outbreaks
Now, meteorologists are warning of a severe weather outbreak, including tornados, for the midwest next week. What do meteorologists look for to predict a tornado outburst days or even a week into the future? First, they look for the jet stream to plunge to the south, bringing strong winds westerly or southwesterly winds and cold air aloft. Second, they look for warm and humid air flowing up from the Gulf of Mexico at lower levels, pushed by southerly winds. Being less dense than the cold dry air, the warm humid air is unstable. The required four ingredients are: warm air, cold air, moisture and winds. Low-level winds blowing with different strength at different elevations set up shearing that produces a horizontal spinning vortex, and regions where winds rise, producing updrafts, draw air flowing along the surface and its vortices in and up. A third layer of air, hot and dry, develops between the lower warm moist air and the colder upper air. This layer acts as a cap that prevents the warm moist air from rising, allowing it to warm even further, creating a positive feedback that makes the instability even greater. As the system moves from west to east across the U.S., the lift increases, the capping dry air is removed and explosive thunderstorms can develop.
The winds circulating around a low pressure center provide a mechanisms that can spin up a normal thunderstorm into a huge rotating vortex known as a "supercell." Supercells contain strong, rotating updrafts. Because they are so big, they are usually isolated from other thunderstorms in the area, sucking up energy and moisture from miles around. Tornados seem to develop within a supercell several thousand feet above the ground. Tornados begin in the supercell as a rotating, funnel-shaped cloud extending from the base of the supercell. When the funnel cloud is half-way between the cloud base and the ground, it formally becomes a "tornado."
BTW, last night was a short total lunar eclipse, and here's a link to a time-lapse of it from USAToday.
Posted by Susan W. Kieffer at 9:35 AM
Friday, March 13, 2015
First of all, where is and what is Vanuatu? It's an island nation of volcanic origin in the South Pacific some 1000 miles east of northern Australia. If you subscribe to the USGS earthquake notification system, you'll see a lot of alerts about earthquakes near Vanuatu. 65 of Vanuatu's 82 islands are inhabited. The islands are steep, prone to landslides and slippages, and there is little permanent fresh water. The shorelines are rocky and drop quickly into oceanic depths because there is no continental shelf. The active volcanoes are Lopevi and Mount Yasur, with eruptions (undersea) recorded in 2008, and another in 1945. About 267,000 people inhabit the islands. Many people live on less than $1/day, and the infrastructure is weak.
|Four cyclones at once|
Although two cyclones in the same basin at the same time is not uncommon in the Atlantic or Pacific, four storms at once is rather rare. There are currently four simultaneously in the southern Pacific: Olwyn, Nathan, Bavi and Pam. There have only been four simultaneous hurricanes at once in the Atlantic two times, in 1893 and 1998.* The 1893 hurricane claimed between 1000-2000 lives in Georgia and South Carolina.
Pam, at category 5, is the strongest storm to make landfall since Haiyan hit the Philippines in 2013. Pam has already hit Port Vila, the capital of Vanuatu, a city of 44,000 people. It is likely to hit southern Vanuatu islands early Saturday morning local time. Pam has sustained winds of 165 mph, but as of the time of this writing (Friday, 1:00 PDT which I think is Saturday at 1:00 a.m. in Vanuatu) the reported gusts have been 60 mph. Storm surge and "very rough to phenomenal seas" are expected to affect particularly the central and southern islands.
It's a bit difficult to know what to believe about barometric pressures, as there are no reconnaissance aircraft in the vicinity. Pressures in the eye have been reported to be as low as 870-890 mbar's. If true, the 890 mb is lower than all known hurricanes except Wilma in 2005 (882 mbar's) and Gilbert in 1988 (888 mbar's). The lowest pressure ever recorded was Super Typhoon Tip (870 mbar's) in 1979.
Why four at once?* There is a wet/dry cycle of 30-60 days known as the Madden-Julian Oscillation, a wave of atmospheric energy that moves east near the equator over these time scales. In one phase, upward motion in the atmosphere is strong, a condition that boosts the formation of thunderstorms. This is the condition now in the western Pacific.This, combined with a strong burst of westerly near-surface winds just south of the equator in the same region this week gave a "boost" to any low-pressure systems trying to get fired up. The result: four storms. See the reference at *, and links within it, for more discussion.
My prayers and thoughts are with the people of Vanuatu as you recover from this storm.
* Discussion from http://www.weather.com/storms/typhoon/news/four-tropical-cyclones-pacific-australia
Wednesday, March 4, 2015
|Villarica eruption March 3, 2015.|
AP Photo/Aton Chile
Villarrica has a persistent lava lake in the bottom of a summit crater. It is ~40 m diameter, and in the early 2000's, it ranged from about 20-100 m below the summit crater rim. In 2004, abundances of gases were measured by Shinohara and Witter, and found to consist of H2O, CO2 and SO2. The gas emissions were the same in the continuous emissions as in lava spattering events, suggesting that the degassing occurs at very shallow levels and that the lava spattering is caused by the bursting of bubbles formed under equilibrium conditions in the magma.
In 2000, in response to a regional seismic event, the eruption of a small volume of lava apparently plugged the conduit (Ortiz et al., 2003) on September 22. On October 5 and 8, a series of explosions reopened the conduit. Ortiz et al. found that the frequency of the harmonic tremor caused a shift in the peak frequency of the tremor from 1 Hz (open conduit) to 2 Hz (closed conduit). (Aside: This is interesting because it is the opposite of normal pipe behavior for which open pipe frequencies are twice the closed pipe frequencies.)
In a textural and geophysical study conducted over a 10-day period in 2004, Gurioli et al (2008) found two types of pyroclasts: scoria and "golden pumice." They have identical glass compositions, but different textures, and the authors concluded that they underwent different histories in the conduit. They interpreted the golden pumice as rising in the expanding inner part of the eruptive jet, and the scoria as forming the outer portion of the jet. The scoria was entrained during passage of fresh material (that became the golden pumice) through older material in the upper portion of the conduit.
Shinohara and Witter, Geophysical Research Letters, 32(20), L20308, 5 pages, 2005
Ortiz, et al., Journal of Volcanology and Geothermal Research, 128 (1-3), pp. 247-259, 2003.
Gurioli, et al., Journal of Geophysical Research: Solid Earth, 113(B8), B08206, 2008.
Posted by Susan W. Kieffer at 10:25 AM
Tuesday, February 10, 2015
|Sample of the 'milky rain' that hit Eastern Washington|
from KOMONEWS.com here
Sample taken in the rain gauge at the NWS office, Spokane
|Summer Lake during an autumn storm|
Image from Wiki here, no attribution given
According to the story referenced in the figure caption, by writers Scott Sistek and Nicholas K. Geranios, the explanation is more close by.
Meteorologists traced the dust backwards to a dust storm over Summer Lake in Oregon on Thursday night. Summer Lake is a large shallow (1 foot-2 feet max depth) alkali lake in Lake County, Oregon. It is surrounded by arid lands, the remnants of an enormous Lake Chewaucan that formed in the late Pleistocene. The last high water was about 13,000 years ago as the Ice Ages ended. As the lake dried up, salts and alkali minerals were concentrated in the remaining waters and in sands and soils around the remaining water. Prevailing westerly winds formed sand dunes that lie on the east side of Summer Lake.
Last week, high winds lofted these dry alkali sands and soils from the desiccated lake bed according to the NWS Mary Wister. Southerly winds then carried the particles northward, carrying the dust a large distance in less than 12 hours. When the dust got into Washington and Oregon, it ran into rainstorms which dragged it down as dusty milky raindrops.
Posted by Susan W. Kieffer at 8:18 PM
Friday, January 16, 2015
|Typhoon Mekkhala at 2 p.m. Eastern Time Friday|
3:00 a.m. Saturday local time in Manila
|Projected rainfall over the next 48 hours in millimeters.|
From the CNN article cited.
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.
Thursday, January 15, 2015
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.
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.
Posted by Susan W. Kieffer at 4:52 PM
Saturday, December 20, 2014
Thursday, December 18, 2014
|Pancake ice on the River Dee|
Photo by Jamie Urquhart, biologist from here
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.
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.
Posted by Susan W. Kieffer at 11:15 AM
Wednesday, December 10, 2014
|Wind gusts forecast for 1:00 p.m. (tomorrow afternoon)|
"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;20725:apafmf>.
http://www.esrl.noaa.gov/psd/atmrivers/questions/ for a summary of into
Sunday, December 7, 2014
|Maule Lake image |
Note the grey lava flow at the bottom center edge of the Lake
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 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
Sunday, November 2, 2014
|Bardarbunga spewing gas from Nature/News|
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.
Sunday, October 12, 2014
|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.
Wednesday, October 8, 2014
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|
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.
Saturday, September 27, 2014
|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)
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.
Tuesday, September 16, 2014
|Mayon volcano, copyright Tom Tam shot from|
Lingnon hill in Daraga Town near the volcano and his home
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.
Wednesday, September 10, 2014
|Sunspot region 2158, the source of a solar flare today|
From Spaceweather.com here
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___________________
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!
Monday, September 8, 2014
|The crater from the meteorite impact|
From this reference
Posted by Susan W. Kieffer at 8:20 PM
Monday, September 1, 2014
|Location of the fissure eruption at Bardarbunga|
from www.bbc.com here
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).
Posted by Susan W. Kieffer at 12:54 PM
Saturday, August 30, 2014
|Credits as above. Picture grabbed from ScienceDaily.com.|
|Stationary rocks (blue arrows) and rock moving from left to right (red arrow)|
|The team used quarried rocks,|
one shown here with its
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
Posted by Susan W. Kieffer at 5:19 PM