Welcome!

This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com


Thursday, June 25, 2015

New Old Faithful Geyser Video available


Jim Westphal (1930-2004)
The results of a video-probe that descended into Old Faithful in 1991 are available on YouTube here (copyrighted video). My colleague in this project was the incredible experimentalist, Jim Westphal of Caltech, we were aided by long-time collaborator and Yellowstone Park geologist, Rick Hutchinson, and the efforts of the U.S. Geological Survey and the National Park Service this year made it possible to get the best possible quality video on-line. The challenges in building this probe were numerous because so little was known about the geometry of the conduit at the time. Literature reports included estimates that the conduit was over 100' long, but the most reliable estimates were smaller than that. We knew that the conduit would be dark and filled with hot steam and we knew that the probe would have to pass through a constriction only 4" in dimension, but otherwise we were descending into the unknown.  In the early 1990's, the cumbersome video equipment of previous decades had finally become small enough that we could design an ice-cooled, self-illuminating, system to lower through the constriction into the conduit.  You can see the camera and the video system as well as the conduit down to about 40' in the video. Enjoy!

Wednesday, June 10, 2015

Wind River earthquake of 2013: unusually deep and in the mantle

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.
Today the BBC has a nice article  by Matt Walker pointing out an article by T.J. Craig and R. Heyburn in Earth and Planetary Science Letters (425, pp. 12-23, 2015) on a very deep earthquake in the Wind River range of Wyoming. The authors point out that while earthquakes in the mantle of the oceanic lithosphere are common, well-documented and well-constrained earthquakes in continental mantle are rare, partly because not only must the depth of the earthquake be constrained, but the depth of the Moho also has to be known. In 2013 there was a M4.8 earthquake in the Wind River Range of central Wyoming, a region that is normally relatively quiet seismically.  Only once in the past ~60 years has a M5 earthquake been recorded, and most quakes do not even exceed M4. This earthquake, and one single aftershock, were initially recorded to be between 70-80 km depth.
     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.

Sunday, May 24, 2015

Texas/Oklahoma flooding, record rains, Lake Texoma flooding

The jet stream patterns that have set up the current
wet situation in Texas. From Weather.com here
on May 24.
Over 350 homes in Hays County, Texas, are gone, and more than 1000 are damaged according to reports coming out this Memorial Day weekend. At least one person in Texas and two in Oklahoma have died as a result of the storms. The Blanco River surged up 28' in 2 hours as the flood surged to 40', three times the flood level.  And as of this (Sunday) evening, more rains are expected, perhaps 3-5" more.
 
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.
spillway of the dam for only the fourth time in its history as the inflow to the Lake is 300,000 cubic feet per second (for reference, this is about ten times the maximum discharge of Glen Canyon Dam, and three times the discharge during the 1983 crisis at Glen Canyon Dam). The Denison Dam here was built during World War II, finished in 1944, in order to control flooding along the Red River. spillway previously in 1957, 1990, and 2007. Water pouring over the spillway goes back into the Red River and is not considered a danger to those living in Denison.

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 explained on Weather.com with the graphic at the top of this post, in April, the conditions that were causing the drought this past winter in California shifted. The subtropical jet has a trough per the southwest, allowing cyclonic storms to breed over the rockies. These, in turn, enhanced the flow of warm moist air up from the Gulf of Mexico for the past six weeks.

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

Magnitude 7.8-7.9 earthquake strikes near Katmandu, Nepal

Location of earthquake and initial aftershocks
From CNN.com
Added on 4/29: Here is a link to an Andrew Revkin article in the New York Times with excellent information about why Max Wyss thinks that the death toll could reach 57,700, and the range of uncertainty. 

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 earthquake struck near noon local time (11:56 a.m.), 11:11 p.m. the previous day, west coast time in the U.S. A magnitude 6.6 aftershock occurred about a half hour later, and strong aftershocks continue. It was centered less than 50 miles west of Katmandu, with aftershocks surrounding the capital on the north and east (see map). Katmandu sits in a valley of 1,000,000 people. There are reports that roads buckled in Tibet, and that avalanches were triggered on Mount Everest. The magnitude of the earthquake has been reported from M7.5-M7.9, and the epicenter at 7-12 km. These estimates should get better as seismologists have time to refine the models and analyze the data, but it is clear that the quake was quite shallow.

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
A 2004 thesis by Bierendra Kumar Piya concluded that there was a significant potential for liquefaction in the Katmandu valley in the case of a strong earthquake. He noted that liquefaction occurred in parts of the valley in the 1934 earthquake, which this one closely resembles, so we expect to see reports of damage to buildings and infrastructure due to liquefaction. There is also a strong possibility of landslides. Dave's Landslide Blog at AGU (starting on April 25, 2015) will be updating and discussing the landslides.

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.

Saturday, April 4, 2015

Tornado outbreaks forecast for week of April 6; lunar eclipse

Dr. Greg Forbes of the Weather Channel
reviewing large tornado outbreaks
Just because I moved out of the Midwest doesn't mean that I have lost my interest in tornadoes! So, to my friends in Illinois, I'm still thinking of you!! Forty one years ago there was a "super outbreak" of 147 tornadoes through Illinois, Indiana, Kentucky, Tennessee, Alabama, Georgia, and surrounding states. All told, there were 147 tornadoes recorded on April 3-4, 1974. This was exceeded only on April 26-28, 2011 when 293 tornadoes were recorded. Joplin, Missouri, was destroyed (more information on this is available in Chapter 8 of my book, The Dynamics of Disaster, shown in the left sidebar).

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.
From here.

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. 

Friday, March 13, 2015

The "Vanuatu Monster" storm

From CNN

From Wiki





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 volcano, Chile, eruption

Villarica eruption March 3, 2015.
AP Photo/Aton Chile
Villarrica volcano is one of Chile's most active volcanoes. It lies along the crest of the Andes in southern Chile, at the west end of three stratovolcanoes that trend perpendicular to the Andes along a fault. The lava is basaltic-andesite and the eruptions are typical Strombolian eruptions that eject pyroclasts several kilometers into the air and lava flows. In 1964 and 1971 massive lahars accompanied the eruptions because of rainfall and melted snow and ice. The current eruption began on February 7th and over 4,000 people were evacuated, but most have returned home as of today as the eruption has waned.

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.

References:

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.

Tuesday, February 10, 2015

Milky Rain in Eastern Washington, a donation from Oregon!

Sample of the 'milky rain' that hit Eastern Washington
from KOMONEWS.com here
Sample taken in the rain gauge at the NWS office, Spokane
Last Friday a "white, milky rain" fell across parts of Eastern Washington, Oregon and Idaho, falling on 15 cities and grabbing headlines even in USA Today. Initial speculation about the cause even included the speculation that it was volcanic ash from a distant volcanic eruption. The Walla Walla County emergency management staff attributed the ash to a January eruption of Shiveluch volcano in Kamchatka, 3000 miles away. CNN meteorologist Derek Van Dam pointed out an eruption two days earlier near Colima, Mexico, 2000 miles away.
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.

Friday, January 16, 2015

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.

Thursday, January 15, 2015

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.  

Saturday, December 20, 2014

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!

Thursday, December 18, 2014

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.

Wednesday, December 10, 2014

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




Sunday, December 7, 2014

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

Sunday, November 2, 2014

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.

Sunday, October 12, 2014

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.

Wednesday, October 8, 2014

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.

Saturday, September 27, 2014

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.




Tuesday, September 16, 2014

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.

Wednesday, September 10, 2014

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: 
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!

Monday, September 8, 2014

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

Monday, September 1, 2014

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).

Saturday, August 30, 2014

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