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

Friday, April 18, 2014

Mexico's 7.2 earthquake and it's early warning system

Seismic record from the Guerrero April 18 earthquake
From Earthquake-Report.com 
A magnitude 7.2 earthquake struck in the Acapulco/Mexico City region early this morning, a Good Friday holiday morning when many residents had apparently slept in or gone away on vacation. The earthquake lasted about 30 seconds. The epicenter was in the state of Guerrero, north of Acapulco. The U.S. Geological Survey has an automatic damage estimator here. The USGS estimates deaths between 1-100, and economic losses between 1-100 million; Max Wyss's estimator at WAPMER predicts 0-50 killed. In spite of damage reports there have been no reports (10 hours later) of fatalities, so there are likely to be very few if any as more information comes in. Why?

One reason that many buildings in the area are built to be quake-resistent because of the history of previous earthquakes. But another reason is that Mexico has an early warning system for earthquakes, and the news has reported that a warning went out about 2 minutes before the quake (I have not been able to independently verify this).

Mexico instituted a Seismic Alert System (SAS) for Mexico city as an experimental project in August 1991. By monitoring the arrival of shear ("S") waves, warnings can be issued before the arrival of the stronger compressional ("P") waves. The system gives, on average, about 60 seconds warning for earthquakes generated in the Guerrero Gap. The quake was the result of a thrust motion where the Cocos plate is being subducted below the North American plate at a rate of about 65 mm/year. The Guerrero Seismic Gap is a ~200 km long segment of this plate boundary that has experienced no significant earthquakes since 1911 (M7.6 at that time). It is thought that an earthquake of magnitude greater than 8 is possible if the entire gap were to rupture at the same time.

The development of the SAS was sponsored by the Mexico City Government, beginning operation in 1991. By the end of the first year, it was experimenting with providing warning to some public elementary schools, and was opened as a public service on commercial radio stations in 1993 after a successful alert that gave 65-73 seconds advance warning during two Guerrero earthquakes (M5.8 and M6) on May 14, 1993. Extensive planning for dissemination and education for the public followed. By 1998 the SAS detected 681 seismic events, 12 of which were strong enough to trigger the general early warning signals in Mexico City, one false one, and one earthquake well detected, but not warned. In the one false alarm, phenomena that were feared--such as panic that could cause injuries--did not occur, but it was realized that many members of the public had not been trained, and training of the public remained a high priority.

The advantages of an early warning system are numerous: Casualties and fatalities are reduced by making people aware that strong ground shaking is imminent. Tsunami calculations can be initiated earlier. Traffic such as trains or subways can be stopped or slowed. The disadvantages or risks are the alerts may not be quick enough  in areas close to the focus of the earthquake and subjected to strong shaking, that there can be false alarms, and that the technique is not good if there are multiple earthquakes close in time or location. Hence, there are tradeoffs between speed and accuracy. Continuous citizen education and awareness must be maintained, and a wide variety of channels of communication must be used to ensure wide dissemination. The private sector must be incorporated into the early warning system so that appropriate services/operations can be shut down for safety.

The Polar Vortex: Good riddance!

I was in Chicago earlier this week, and it was freezing cold once again. My friends in Illinois have had a miserable winter and it wasn't letting go easily. As I started to look at why it was so cold there mid-April, I discovered that I had a post that I started in the winter and didn't finish. It was about the "polar vortex," and I realized that I don't know very much about this thing. So, belatedly, here's my introduction to myself about the polar vortex. For more details and the references from which I took this material, see Skepticalscience, an excellent resource on climate, and the weather.com post here.
     We live in a portion of the atmosphere called the troposphere, and most of us have heard of the stratosphere, the layer of the atmosphere above the troposphere. The boundary between the two is the tropopause, and it's altitude varies considerably with the seasons. We in North America also live in the mid-latitudes, a region of mild temperatures that extends very very roughly between 30 and 60 degrees latitude. North of this (in the northern hemisphere, the reverse in the southern hemisphere) is the very cold polar air. The boundary between the two is the Polar Front, a collision zone between the warm moist and cold dry air.
Typical polar vortex position on the edge of the
polar high (not shown). Graphic from weather.com.
     The collision zone between the two big air masses results in very high winds at high altitudes at the top of the troposphere. In the northern hemisphere, this is referred to as the Polar jet stream. It is strongest in the winter when the temperature contrast is the greatest between the polar air (because there is no sunlight) and the temperate air of the mid-latitudes (which may seem cold, but is nothing like the Polar air!)
Distorted polar vortex (from same weather.com site as above.
      The polar regions are areas of high atmospheric pressure covering the north and south poles. On the borders of the polar highs are polar vortices (sometimes called polar cyclones or polar lows). These are permanent areas of cold, low pressure in the upper atmosphere that draw their energy from the temperature difference between the cold polar air and the warmer air of the midlatitudes. They are, therefore, strongest in the winter.    There are typically two polar vortices in the northern hemisphere--one near Baffin Island and the other over northeast Siberia.The air in them spins counter-clockwise. (Only one of these is shown in the graphics here.)
    The polar vortex is contained by our jet stream (typically at around 35,000 feet altitude where airplanes fly).  The jet stream is normally rather loopy, an instability known as Rossby waves, that arises because the Coriolis effect has a different magnitude at different latitudes. When one of loopy parts of the jet stream tokes an unusually deep plunge southward into the midwest, it brings air from the polar vortex and freezing temperatures southward. Note in both of the graphics that the main location of the low pressure zone stayed up north over Baffin Island, it's permanent home.
     The cold air aloft in the polar vortex sinks to the ground, displacing the lighter warmer (winter) air normally there. Rossby waves migrate, typically to the east, and so the disturbance moved on out of the midwest. Things  warm up, and Chicago goes back to balmy 30+ degree nights in the winter!

Tuesday, April 8, 2014

USGS updates information on Oso landslide

Here is an update on the Oso landslide from the USGS.

Wednesday, April 2, 2014

E-an Zen: 1928-2014

My great friend and mentor of many decades died on Saturday a.m. after a long battle with cancer.

His life was so rich that I'd like to share the tribute to him written by Andrew Alden on Geology.about.com:

Andrew, thank you for this wonderful tribute and for preserving my description of being in the field with him!

E-an, whereever you are, we all miss you!

"One of America's unsung senior geologists, E-an Zen, died on 29 March at the age of 85. Born in China, he emigrated to the U.S. and earned a doctorate in 1955 from Harvard. A 30-year career followed at the U.S. Geological Survey, then 23 more years on the faculty of the University of Maryland. He was basically a mineralogist, but his field skills were formidable and he made large contributions to Appalachian geology, metamorphic petrology, and mapping of northern Rockies. Anyone who's looked into the literature of those fields has read his papers. He earned his full share of awards: membership in the National Academy of Sciences, the Geological Society of America's Day Medal, the Mineralogical Society of America's Roebling Medal, the Geological Society of London's Coke Medal, and more.
In 1991 Susan Werner Kieffer, no slouch herself, recalled fieldwork with Zen: "I pride myself on being fit, but when I'm in the field with E-an, I'm always so out of breath that I can't talk, and thus I'm subjected to questions. For example, I was recently subjected to 3–4 days of questions about granites, migmatites, structural geology, epidote, and eucalyptus while working with E-an at the Cooma Granite in Australia. . . . I was so out of breath and confused by the rocks we were in that I wasn't providing him any feedback. E-an could sense my frustration and, with the sensitivity so characteristic of the man, politely changed the questions: to ones about scientific ethics, education, literacy, policy, religion, or philosophy—subjects about which he is deeply concerned."
Those wider concerns marked Zen's tenure as president of the GSA in the early 1990s. In hisPresidential Address of 1992, published in GSA Today, he told his audience, "Science is too important to be left to the scientists. Geology directly impinges on human welfare and so cannot be an ivory-tower science. Conservation of the environment, discovery and recovery of Earth's resources, avoidance of natural hazards, disposal of wastes, forecasting of global change, decisions on land use, equity for the future—these and other issues need geological knowledge both for technical resolution and for guiding public policy. Public policy needs public support; we ignore the public at our peril." He went on to discuss scientific literacy, ethics, education and geologists' obligation to do public outreach.
I wasn't there that day, but I recall being impressed when I read his words, and I continue to take his ideas seriously in my work here on About.com."

Tuesday, April 1, 2014

UPDATED: Chile earthquake and tsunami on April 1; 900,000+ evacuated

Map of South American
subduction zone and significan
earthquakes. From
Susan Bilek reference listed
below at **.
A powerful earthquake off shore of Chile has generated a tsunami that has already produced six-to-seven-foot waves that have struck the beaches. The earthquake was centered about 60 miles northwest of Iquique and at a depth of about 12-13 miles. A tsunami warning has been issued for Colombia, Panama and Costa Rica, and geoscientists are working to determine the magnitude of tsunami waves at Hawaii and as far north as North America. UPDATE: Tuesday afternoon--The government of Chile has reported over 900,000 evacuated; CNN has reported a million. The major problem appears to be serious structural damage to poorly built homes.
      Chile has been subjected to powerful earthquakes several times over the past century: November 11, 1922, a magnitude 8.5; May 22, 1960 a magnitude 9.5; February 27, 2010 a magnitude 8.8, and today, a magnitude 8.0 or 8.2 (magnitudes are being revised as I write this). Charles Darwin experienced the 1835 earthquake in southern Chile in 1835, one that had a magnitude of 8.1 or 8.2. It triggered a tsunami that destroyed Talcahuano and devastated Concepcion. In this tsunami, a schooner was swept 200 meters inland. The earthquake took place in the middle of the day and inhabitants had time to run into the hills so the death toll was fortuitously low. Historical records going back to the 1500's suggest other great earthquakes.
Geometry of the plates around South America
From Wiki here
     Why is Chile so prone to these quakes? Off the west coast of Chile, the Nazca plate is diving down (being subducted) below the South American plate.  The Nazca plate is relatively young, having formed when the now-defunct Farallon plate split about 22.8 Mya split into the Nazca and Cocos plates. The plate is being subducted at a rate of 3.7 cm/year, one of the fastest motions of any tectonic plate. It dives so deeply under the South American plate that it even influences the geology and geography of Bolivia far inland to the east. The 1994 Bolivia earthquake of magnitude 8.2 occurred on this place and is renowned as the strongest earthquake occurring deeper than 300 km.
Susan Bilek's model of the role of heterogeneities
in subduction zone dynamics.
    In a nice review paper**, Susan Bilek discussed how the heterogeneity of the subducted plate causes there to be a wide variety of rupture modes along this zone, ranging from "magnitude >8 events during one century followed by smaller ones in other time periods, as well as unusual tsunami events." Her idea of the effect of heterogeneity is shown on the figure attached. The idea is that as various geographic features on the subducting plate--such as seamounts and ridges--enter the subduction zone, they change the friction in the zone. This acts, along with variations in the thickness of sediments in the overriding plate and in pore pressure in the sediments, to produce variability in the slip mechanisms along the fault.

**Bilek, Susan L., Invited Review Paper: Seismicity along the South American subduction zone: Review of large earthquakes, tsunamis, and subduction zone complexity, Tectonophysics, 495 (2010), 2-14.

Sunday, March 23, 2014

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

Oso, Washington, is at the marker. Arlington is to
the left, Darlington is to the right by the magnifier bar.
The slide at Oso cut off Highway 530 between
Arlington an Darlington.
**Chapter 4 in my book "The Dynamics of Disaster" is titled "The Flying Carpet of Elm" and discusses the factors that influence landslides. It also discusses the mother of all landslides, a slide that occurred 50 million years ago in Wyoming, covering 1300 square miles and traveling more than 30 miles.

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

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

The SeattleTimes is providing excellent coverage.

Take I-5 north from Seattle about 50 miles through Everett toward Arlington, and turn east onto Highway 530, which takes you south of Mount Baker. Along this road is the small town of Oso, population about 200. At about 11:00 this morning, a massive slide of mud, rocks and trees travelled a mile down near Oso, taking down at least 6 homes, killing at least three people and trapping others. (As of Monday morning, 18 are still missing.) Three more are reported in critical condition.The slide was at the 29400 block of SR 530 near milepost 37, between the cities of Arlington and Darrington. It landed in the path of the Stillaguamish River, reducing its level at one spot from about 3.1 feet to 0.9 feet, indicating that the slide appreciably blocked the river. The state hydrologist reported that 15-20 feet of debris blocked the river, and that its flow had been reduced to about 1,000 cubic feet per second. Other reports have said that the slide is 135 feet and 180 feet deep.
Image of the landslide from Seattle Pi
     In situations like this where an earth slide blocks a river, the concern is that water will pond behind the blockage forming a lake, and that the blockage--a dam--will suddenly collapse and release the water catastrophically. The National Weather Service has said that for this to occur the water would have to be blocked for 36 hours, and then released within an hours time.
     Snohomish county officials have advised residents downstream of the slide to evacuate their homes as "It is going to break loose and the question is how and where" (John Pennington with the Department of Emergency Management (quoted from King5 news here).
     The National Weather Service has issued a flash flood watch through Snohomish County through Sunday afternoon. The ground is saturated with water from recent rains, flash flooding is possible, and the saturated ground combined with rain is believed to be the cause of the Oso mudslide. Flood alerts have been issued both upstream and downstream of the slide.
Image showing the abundance of water at the base of the slide.
From Seattle Pi
     UPDATE: Several serious hazards remain in this area. The first is the landslide material itself. It is composed of a lot of fine grained materials, sand and clay, that form a nasty, hazardous substance called "quick sand" or, depending on particle size, "quick clay." Quick clay was the cause of the landslide from which the title of my book chapter, The Flying Carpet of Elm, was taken. I'm not sure of the exact geology of the Oso area, but it looks like the materials are a watery mixture of very fine particles. These materials, if undisturbed, can be very strong, forming the slopes on which homes and other buildings were built in the area. But, when disturbed, in an instant under certain conditions of stress, the state of the materials changes to liquid. Although some of the water visible in the images (to the right) may be from the dammed river, it looks like a lot of the water came from within the landslide itself.
     The second major hazard arises from the partially blocked river. These landslide dams are not strong and eventually, sooner or later, the water will either erode through the toe of the dam (the best outcome) or the dam will break (worst outcome). Until equilibrium is restored, downstream residents and infrastructure are at risk. Apparently a major bridge on Highway I-5 is being watched carefully because the pilings holding it up are old and not as deep as would be built under newer bridges.

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

Friday, March 14, 2014

Happy Pi Day!

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

32 ft/sec^2
32 ft/sec^2
100 ft/sec
(1/2 provided your initial velocity is zero)
320 ft/sec
160 ft/sec
1600 ft
200 sec
49,000 m
980 m/sec
102.4 ft/sec
100 lbs
37 degrees
45 degrees....

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

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

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

Monday, March 3, 2014

Corvettes and sinkholes: what is a sinkhole?

1962 Black Corvette
from Roscoe-Restoration.com
A few weeks ago, a sinkhole swallowed eight valuable Corvettes at the National Corvette Museum in Bowling Green, Kentucky, and today the news is that the recovery of the cars has started. Here, from CNN.com, is a list of the cars:
-- a 1962 "Black Corvette"
-- a 1984 PPG pace car
-- a 2009 ZR1 "Blue Devil"
-- the 1992 white "1 Millionth Corvette"
-- a 1993 ruby red "40th Anniversary Corvette"
-- a 2001 Mallett Hammer Z06 Corvette
-- the 2009 white "1.5 Millionth Corvette"
-- a 1993 ZR-1 Spyder
The museum estimated millions of dollars in damage. The sinkhole was approximately 40 feet in diameter and 20 feet deep.
    What causes sinkholes? A glimpse at this fascinating map of Kentucky groundwater flow routes confirms the well-known fact that sinkholes are not uncommon there, given features with such names as "Sinking Creek", "Auburn Bluehole," and "Lost River Rise."
Simplified geology of Kentucky
from Geology.about.com.
     Bowling Green lies in the south-central western portion of Kentucky in rocks of Mississippian age (359-323 million years ago; comprise about the lower (oldest) 2/3 of the Carboniferous rocks). In Kentucky, the Carboniferous Series rocks (359-299 m.y. ago) contain massive amounts of coal, and are so abundant that they are subdivided into the Mississipian and Pennsylvanian. They are the thickest in the Appalachian Basin in the eastern portion of Kentucky, and the Illinois Basin in the west.
      The Mississipian rocks of western Kentucky are comprised mostly of limestones, shales and sandstones. The limestones contain a oil reservoirs underground and where exposed at the surface, the limestone is quarried--the Reed quarry producing more limestone than any other quarry in the U.S. The limestone also includes Mammoth Cave, part of the Mammoth Cave-Flintridge system, the longest cave system in the world. These limestones were deposited in shallow seas.
Karst features from UTexas here.
     Limestone is dominantly composed of calcium carbonate, CaCO3. This mineral is quite soluble in water containing CO2 through the reaction:

CaCO3 + CO2 + H2O → Ca(HCO3)2

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


Tuesday, February 11, 2014


Ice storms are very bad for trees! NOAA image from here.
(I have no idea how blogger put the "U" on this post, nor any idea how to get rid of it....Grrrr....)

The CNN  headline today is "Forecast: Historic, crippling, catastrophic ice: Atlanta prepares for the worst." It is well known that freezing rain storms occur frequently in the southeastern part of the U.S. They are beautiful, but dangerous and costly.

And, they are not all that rare. Montreal, Quebec, typically receives freezing rain more than a dozen times a year. In 1998 the great North American ice storm of January 5-9 was one of the most damaging and costly ice storms in North American history, causing massive power outages on the east coast. Eastern Canada bore the brunt of the storm. Millions were without power for days to weeks to even months. 35 people died, a significant number from carbon monoxide poisoning from generators they used to try to keep themselves warm. The effort to reconstruct the power grid led to the biggest deployment of Canadian military personnel since the Korean War.
What makes an ice storm? The attached graphic from Gay and Davis summarizes the types of precipitation nicely and, when I read their paper, I learned a new word: "hydrometeor." It is "any water or ice particles that have formed in the atmosphere or at the Earth's surface as a result of condensation or sublimation." Examples are clouds, fog, rain, snow, hail, dew, rime, glaze, blowing snow and blowing spray.

Vertical temperature profiles in the atmosphere and
the kind of storms that they produce. From Gay and Davis,
1993 here.
The graphs shown here summarize the general conditions under which snow, sleet, freezing rain, and rain land on the ground within the context of the atmospheric temperature distribution.** Consider the situation when a warm front moves in.  If warm front isn't too strong, the atmosphere remains cold (below freezing) throughout, and precipitation falls in the form of snow. But, as a warm front moves in, an inversion layer develops with cold air near the surface under the warm air aloft. If snow starts falling aloft and encounters this warm air, the snowflakes melt. A mixture of frozen and unfrozen "hydrometeors" develops in the warm layer (left side of the Figure shown here). As these hydrometeors fall into the near-surface cold layer, they get supercooled. Any icy snowflakes that didn't melt as they traveled through the warm layer become efficient sites for refreezing, and a mixture of snow, ice, and some liquid falls to the ground, i.e., sleet. As the warm layer develops (gets warmer and thicker), all of the snowflakes melt as they travel through it. Without nearby ice particles to serve as nuclei, these become supercooled as they fall through the cold layer near the ground, i.e., they are supercooled liquid. When they land on cold ground, they freeze, producing freezing rain. If the liquid droplets formed in the warm layer reach ground that is above freezing temperature, the precipitation is cold rain.

As the warm front develops, it is common to see a sequence of precipitation progress from snow to sleet to freezing rain to rain.  The reverse situation occurs with cold front events in the southern Plain states.

A few factlets from Wiki: The thickest recorded ice accumulation from a single ice storm in the U.S. is 8 inches (northern Idaho, January 1961). In February 1994 a severe ice storm caused over $1 billion damage in the southeast.

**This discussion is from David Gay and Robert Davis, "Freezing rain and sleet climatology of the southeastern USA," Climate Research, vol. 3, 209-220, 1993. Notably, they comment that at the time this paper was written, relatively little was known about freezing rain and sleet climatology.

Sunday, February 9, 2014

Meteorite impact craters and their rays

Martian impact crater formed between July 2010 and
May 2012. NASA image ESP-034285_1835
NASA just released this beautiful image of a fresh Martian impact crater. The image came from HiRISE on NASA's Mars Reconnaissance Orbiter taken on November 19, 2013. The age range was pinpointed through the orbiter's "Context Camera" that revealed a change in appearance at that site between July 2010 and May 2012. The crater is about 30 m in diameter, and the ejecta extends out to 15 km. The blue color in this image is attributed by the HiRISE team to removal of reddish dust in the area. Alternatively, I'm wondering if it sue to the veneer of fresh excavated ejecta covering the reddish dust.

In discussing this with a colleague, I pointed out that many of the studies of impact ejecta processes date back to the 1960's and 1970's, and were in the context of where to send an astronaut to explore on the Moon.  If you wanted to sample material from deep in the crust, it would be too hazardous for an astronaut to climb down the walls of an impact crater (believe me, having scrambled around the walls of Meteor Crater in Arizona many times, you do not want to be wearing a space suit while climbing down into an impact crater!). One thought was that you could sample the ejecta by going to the rays of a crater. For example, from this source:

"Lunar crater rays are those obvious bright streaks of material that we can see extending radially away from many impact craters. Historically, they were once regarded as salt deposits from evaporated water (early 1900s) and volcanic ash or dust streaks (late 1940s). Beginning in the 1960s, with the pioneering work of Eugene Shoemaker, rays were recognized as fragmental material ejected from primary and secondary craters during impact events. Their formation was an important mechanism for moving rocks around the lunar surface and rays were considered when planning the Apollo landing sites. A ray from Copernicus crater crosses the Apollo 12 site in Oceanus Procellarum. Rays of North Ray and South Ray craters cross near the Apollo 16 site in the Descartes Highlands and a ray from Tycho crater can be traced across the Apollo 17 site in the Taurus-Littrow Valley on the eastern edge of Mare Serenitatis. There is still much debate over how much ejecta comes from the primary impact site or by secondary craters that mix local bedrock into ray material."

In a 1971 article, Verne Obereck concluded that the bright rays "only reflect local excavation of mare substrate material by myriads of small secondary or tertiary impact craters:"

Observations of high resolution photographs of part of one of the prominent rays of the lunar crater Copernicus show that there is a concentration of small bright rayed and haloed craters within the ray. These craters contribute to the overall ray brightness; they have been measured and their surface distribution has been mapped. Sixty-two percent of the bright craters can be identified from study of high resolution photographs as concentric impact craters. These craters contain in their ejecta blankets, rocks from the lunar substrate that are brighter than the adjacent mare surface. It is concluded that the brightness of the large ray from the crater Copernicus is due to the composite effect of many small concentric impact craters with rocky ejecta blankets. If this is the dominant mechanism for the production of other rays from Copernicus and other large lunar craters, then rays may not contain significant amounts of ejecta from the central crater or from large secondary craters. They may in fact only reflect local excavation of mare substrate material by myriads of small secondary or tertiary impact craters.

Recently, Valery Shuvalov proposed a ray production mechanism based on a large supercomputer simulation. In this simulation, the hypothesis was that rays result from interaction between the shock wave associated with a developing crater and nonuniformities in the target surface. The results of a simulation of the formation of a crater by a 5-km diameter asteroid on the Moon at an impact velocity of 15 km/s are shown in the adjacent figure. This impact would have produced a crater approximately the size of Tycho, a famous rayed crater on the Moon. The target and projectile material were both assumed to have the mechanical properties of granite.

When the shock wave from the developing primary crater hits a depression (preexisting small crater) a jet of material is spalled off the wall of the small crater proximal to the primary crater (upper left in the simulation sequence shown).  In contrast to the effect of a depression on ray formation, a ray-suppressing effect is seen if there is a nearby elevation.

Monday, February 3, 2014

Eruption of Mount Sinabung, in North Sumatra, Indonesia

Photo from CNN.Com by Einsar Bakkara/AP
in the cited article in text
(if I read the credit correctly)
Mount Sinabung, an Indonesian volcano dormant since 1600 came to life in 2010 and, on Saturday, spewed forth pyroclastic flows that killed at least 14 people. Tragically, it appears that these people had been evacuated last summer and only the day before this eruption, had been allowed to return to their villages. The Wiki site for Mount_Sinabung appears to be updated in a timely way, so I won't go into details here.
     It is difficult to tell what the source of the erupted material is in detail, but from photos of the volcano (a classic beautifully conical stratovolcano) and the lack of any indication of lateral bulges on the flank, a good assumption is that the flows are originating in a summit crater. A question/assumption, is whether they are being driven by volatiles (presumably H3) from magma or whether or not groundwater is involved. According to the Wiki article, in late December, a lava dome had formed on the summit.
     The eruption gas/ash material from lava domes results in eruptions known as "Pelean" or "Merapi"-type pyroclastic flows. Two processes contribute to the high-velocities observed from such eruptions: gravitational collapse (supplemented by heating and expansion of entrained air), and sudden expansion of pressurized gases from inside the domes. If gravity controls the energy transfer, then areas affected can be predicted on the basis of topography. If gas expansion adds a significant contribution, which is likely in the proximal region around a dome, then velocities beyond those acquired by acceleration in a gravitational field, exist, and these imply that much larger areas are at risk than might be predicted from the gravitational forces alone.
     In 1993, Jonathan Fink and I published a paper "Estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes," Nature, v. 363, pp. 612-615, 1993.  In this paper we examined the two processes above, and concluded that the decompression process produces velocities comparable to those acquired by gravitational accelerations. In snapshots, such as that in the photo in this post, my guess is that the flow is clearly already some distance down the slopes of the volcano where it has assume the classic profile of a dense gravitational flow with air entrainment. More proximal regions have already been hit, and are, apparently, where the casualties have occurred. With the complicated sequence of recurring explosions/eruptions from the summit, it may never be possible to reconstruct the dynamics of the flows in the proximal region.

Monday, January 27, 2014

Avalanches block highway, isolate Valdez, Alaska

The avalanche on Richardson Highway near Valdez
Alaska Department of Public Transportation and
Public Facilities
Reuters photo from here.
Update: The road appears to have been reopened on Feb. 6.

Last Friday avalanches ranging up to hundreds of feet in length and 30-40 feet in depth blocked the Richardson Highway leading to Valdez, Alaska, a town of 4,000 people. This highway connects Valdez to the rest of the Alaska Highway system (however, supplies can be brought into the town by ship.) An even larger avalanche occurred on Saturday, and a 50 mile stretch of highway has been closed (it is impressive that it takes the helicopter nearly two and a half minutes to fly the length of the impounded lake and avalanches.) Here's a great video, courtesy of Josh Miller and Douglas Fulton of Vertical Solutions, of a helicopter flyover of the avalanches and impounded use/debris/water lake. There is some hope of digging the residents out by tomorrow (Tuesday), but the city officials are asking residents to plan to be there at least a week. There are multiple avalanches across the highway.
     One potentially serious problem is that one of the slides created a snow dam in Keystone Canyon that has impounded the Lowe River, and although some of the water is draining through an old railway tunnel, the potential for an ice-dammed lake breaking is real. The Alaska Department of Transportation says that it is too dangerous to work on clearing the slide until the lake drains because of fears that digging on the downstream side could trigger a surge of water. The National Weather Service issued a flood watch on Monday for residents downstream of the ice dam, saying that the ice dam could collapse with "little or no warning."
     According to the Alaska Avalanche Information Center more than 3" of rain on 24 hours, combined with abnormally high (above freezing) temperatures over the past 10 days caused conditions conducive to avalanching. Some reports suggest water up to 40' deep behind the ice dam.
    Much is being made of the fact that Valdez is much warmer than the mid-section of the US, currently experiencing another Arctic blast. Valdez has been in the 40's, and some parts of Alaska could even be in the lower 60's this week. Spring has, simply, started early in Alaska.

Tuesday, January 21, 2014

50' waves for Hawaii, and crummy surfing? What's the problem?

From CNN.com here, photographer is
Kent Mishmura, Getty Images.
When the surf is just right, surfers of the world gather in Oahu for "just one day of quality surf" when wave heights reach 40' or more, the largest waves since 2004.. The National Weather service has issued an gale warning that "An extremely large northwest swell will roll through the area Tuesday through Thursday." The significant wave height is expected to reach 20 feet (significant wave height is the average height of the highest 1/3 of the waves, and individual waves can be more than twice this value.) The large northwest swell is arriving Tuesday night, producing high surf along the north and west-facing shores of the islands over Wednesday and Thursday.
     I couldn't find any specific reference to the source of the northwest swell. There are two storms listed here, Tropical Storm LINGLING, and Tropical Depression INVEST, and I'm assuming that one or both are the drivers of the swell. However, neither of these is mentioned in the 1/21/2014 NOAA description of conditions appended at the end of this post. (Note that it discusses both big waves during the past week, and forecasted for the next few days.) NOAA attributes the waves to a low with hurricane force winds far to the northwest of Hawaii.

     Countering this driver of good big waves is a fast moving cold front approaching Kauai from the northwest.  This front will cause southwesterly winds to increase over Oahu and Lihue (the two northernmost large islands in the Hawaiian chain) over the next two days (Tuesday and Wednesday), and the winds will then spread southeast down the other islands. The front will produce gusty winds and the gusty winds will destroy the "quality" (a quote from Glen Moncata, the organizer of a potential big surf competition) of the waves required for prime surfing conditions.
    Aside from cancellation of a potential big surf event, there is a geologic implication in all this: beach erosion on the North Shore may be severe. It is an ongoing problem in Hawaii, and reports are that there are a number of North Shore homes that may be imperiled by the wave action.

The NOAA statement: of 1/21/2014:

Summary: overlapping winter caliber events.
Detailed: mid Friday on northern shores has extra large breakers, meaning surf on outer reefs, from 295-320 degrees with 12-17 second periods. Heights should lower on Saturday.
A strong jet stream has been steering a series of deep surface low pressure systems across the NW to N central Pacific since 1/11. This active pattern should keep events peaking above winter average levels arriving locally with a 1-2 days spacing 1/18-25.
A complex pattern produced the extra-large surf of 1/17. There were two remote separate low pressures cells and associated fetches and a nearby fetch area of gales. The longer-period swell from the remote sources peaked Thursday afternoon into the night. The nearby gales had significant westerly component, as seen by comparing peak wave heights from the Hanalei and Waimea buoys, 19 feet and 15 feet, respectively for overnight to morning 1/17. The more westerly component is shadowed on Oahu by Kauai. The second low pressure of the remote low cells had an associated captured fetch over the 305-320 degree band that stretched from the Kuril Islands to near 30°N, 170°W, or over 2200 nm, making for a long-lived event. Jason altimeter data from 18Z 1/16 in a region about 1000 nm away gives confidence for continued elevated surf on Saturday 1/18 from 305-320 degrees, nosing down below extra-large.
The complex pattern simplified to one deep low pressure cell that occluded near 40°N, 160°W on Thursday 1/16. The center of this low tracked N to the Aleutians by early Friday 1/17. Severe gales over the 340-360 degree band, and angular spreading from seas aimed E of Hawaii should allow moderate energy from 330-010 degrees building late Saturday, peaking Sunday, and dropping Monday.
Further west, a new low pressure cell intensified near 35°N, 175°E Thursday afternoon. This hurricane-force system crossed the dateline Thursday night near 38°N, and is modelled to be north of Hawaii near 40°N by Saturday morning. With a compact size and fast track, the fetch areas are limited in length and duration for growth of seas. The GFS input to Wave Watch III, ww3, predicts the peak near dawn Sunday morning with 12 feet at 17 seconds from 320 degrees. This forecast /was' predicting higher swell for two reasons. First, the ww3 has shown a low bias for sources of gale or stronger winds with fetch heads within 1000 to 1500 nm away. Second, there was a historic low pressure cell with similar track, track speed, size, and depth of central pressure January 8-9 2004 that resulted in Waimea buoy showing a short-lived maximum above 18 feet at 20 seconds on January 10, hence, giant surf. This duration of the most elevated heights is expected to be short, about a 12 hours, centered on late Sunday morning from 300-320 degrees.
However, Sunday morning update, overnight observations from buoy 51101 northwest of Kauai indicate that swell heights are not as large as originally anticipated, and are running slightly lower than Wave Watch III guidance. Therefore, this swell forecast has been lowered, closer to Wave Watch III guidance, for Sunday.
Surf should drop to within high to extra-large on Monday from 310-330 degrees as a new event arrives.
A new surface low pressure is piggy-backing the hurricane-force system near the dateline on 1/17. The new cell is modelled to be weaker with a E track about a day behind. Gales to severe gales are modelled to set up over the 315-330 degree band, reaching to within 1000 nm of Hawaii on Sunday. Forerunners are due locally Monday afternoon, with the event peaking in the wee hours Tuesday. Heights should slowly decline into Tuesday night as a new event arrives.
Models are showing a surface low pressure deepening to hurricane force west of the dateline 1/19, tracking east across the dateline near 40°N 1/20, continuing east to near 165°W near 40°N Tuesday, then turning north into Wednesday. This should make for giant surf by the wee hours 1/22 from within 290-330 degrees. The track, track speed, size, and depth of central pressure are similar to low pressure systems that generated giant surf locally of January 28, 1998, February 23, 1986, and December 1 and 4, 1969. It is too early for specifics, other than noting that this could potentially be the type of surf episode on order of decadal turn-around. This type of surf episode is not only well above average, but long-lived, on the order of 24-36 hours, which makes for greater coastal impact. Local tides will be in the neap phase 1/22-23 which offsets wave run up potential. It is worthy to note that Dec 1-4, 1969 saw extensive coastal wave wash under neap tide conditions, offset by the surf magnitude on order of 50-100 year turn-around.
Windswell through the period should be minimal from 40-90 degrees. See the latest NWS state weather forecast discussion regarding the gentle local wind pattern of varying direction. Moderate to fresh breezes 1/22 could bring small chop from 180-315 degrees 1/22.
The size of the present and upcoming surf events 1/17-25 can refract waves into most coastal areas of Oahu regardless of orientation.
Surf should increase from the southern hemisphere on Tuesday 1/21 from 190-200 degrees. A severe gale to storm-force fetch set up S to SE of New Zealand 1/13-14. New Zealand shadowed the fetch when winds were strongest. As the associated low cell tracked east clear of the shadow, winds weakened. Only a small episode is expected peaking Wednesday 1/22 from 190-200 degrees.
Into the long range, another fetch set up in a similar location and of similar strength S to SE of New Zealand 1/16-17. However, the head of the fetch reached further north to near 40s, or about 4000 nm away. This should give a notch higher surf locally, building 1/24, peaking 1/25, and dropping 1/26. There could be one more small, long-period event from 190-200 degrees locally 1/28-29.
In the northern hemisphere, extra-large to giant, declining surf from 300-340 degrees is suggested for 1/23. Winter caliber lows are expected to continue forming near 40°N in the NW to central N Pacific, with the next high to extra-large event hinted for 1/24-25 from 305-320 degrees. Minimal windswell from 40-90 degrees should hold 1/23-25.
Long range forecasts are subject to high uncertainty.
This collaborative forecast will resume on Tuesday, January 21.
This forecast was produced through the collaborative efforts of NWS and NCDDC. Please send suggestions to w-hfo.webmaster@noaa.gov or call the Warning Coordination Meteorologist at 808-973-5275.

Monday, December 30, 2013

Australian icebreaker nearing Akademik Shokalskiy ship in Antarctica

View from the Akademik Shokalsky a day ago
from the NYTimes.com 
Nearly a week ago, the Russian ship, Akademik Shokalskiy ship became trapped in ice in the Antarctic. The ship is an ice-strengthened expedition vessel, currently carrying both tourists and scientists studying environmental change near Cape de la Motte, about 1,700 miles south of Hobart, Tasmania. Strong winds pushed the ice pack against the ship, with ice thicknesses around 10 m. Earlier a Chinese vessel, the Xue Long attempted the rescue, but was frustrated by thick ice over the weekend.
The Russian icebreaker Krasin leading
an American supply ship into McMurdo Station
from Wiki here.
     Now, the Australian icebreaker, the Aurora Australis, is only 11 nautical miles from the ship and nearing a rescue. At the moment, the link above shows the view from the ships webcam! So, how do icebreakers work? The primary job of the icebreaker is to crush the icpack and move it aside whiteout becoming stuck itself. According to Marshall Brain on "How Stuff Works", an icebreaker has characteristics that help it do this: (1) a high-strength hull; (2) a large mass to help it maintain momentum so that it doesn't get stuck itself; and (3) power to overcome the drag of the crushed ice. Must be a noisy place!
     Here's a bit more from Wiki: The icebreakers push straight into the ice, breaking up the ice, sometimes even driving its bow onto the ice surface so that the weight of the ship helps break up the ice. The design of the hull is such that the broken ice is then directed around or under the vessel. The design is also optimized to minimize damage to the propellers and other parts of the icebreaker itself. Icebreakers have variously been steam-powered, diesel -powered, and nuclear-powered. They have been designed to function on rivers (e.g., in Europe) as well as on the open ocean. The photo shown next is of a successful rescue.

Sunday, December 22, 2013

On the fluid dynamics of gold, as in "gold, incense, and myrrh" this Holiday Season!

Gold leaf temples in Bagan, Myanmar
from http://images.smh.com.au/2012/01/27/2919441/art-Burma-Bagan-Temples-420x0.jpg
OK, so gold (a precious metal), frankinense (aperfume or incense), and myrrh (an oil) were given to Kings and other important persons in biblical times. Why? Gold, perhaps representing kingship; incense symbolizing a priestly role, and myrrh, a symbol of death and embalming.
     Well, let's stick to a more-or-less geological topic here, and look at the unique properties of gold, a substance so soft that it almost qualifies for discussion on this blog of "geology in motion." That is, let's look at how gold leaf is produced. It's a long involved process, involving human labor that has changed little in 5,000 years since artsans in Egypt recognized the ductility and its possibility for use. On this website, is the statement that the amount of gold that would fit inside a tennis ball is enough to cover (gold-leaf covered) the dome of the capital building in Atlanta, Georgia!

(In researching this, I discovered a Wiki article on the "Georgia Gold Rush" that might e of interest to the readers.
The Atlanta Georgia capital. The gold leaf was
added in 1958, with native gold leaf
from nearby Lumpkin  County,
where one of the
first American Gold Rushes occurred
in the 1830's.
Paraphrasing and quoting from here, the basic process is this:
Gold is typically mixed with an alloy such as silver or copper to make a grade of gold described by the "carat" system. Goldbeaters typically make 23 carat gold.
     The gold, along with its added alloy metals, are melted in a furnace, and then poured into a cast to make a bar. This bar is then put through a series of rollers, adjusted repeatedly until the bar becomes a sheet 1/1000 of an inch thick.
     But, this is not the end of the process. The gold is then cut into one-inch squares and beaten on large blocks of marble and granite, and, amazingly, ends up with a sheet that is only 1/2500,000 inch thick.
     Along the way, the gold has been cut into one-inch squares and been beaten by hammers. The first stage is referred to as the "cutch."  In it, about 150 skins (formerly ox intestines, but now, Mylar or parchment) surround the gold to hold it together during the beating. Finding something that can withstand the repeated pounding was a challenge. Blocks of marble and granite are used, sometimes placed onto the top of a tree trunk or set deep into the ground to create resiliency. The beaters spend an hour, using a 15-pound hammer and striking the gold about 70 times per minute, while also rotating and turning over the gold alloy packets to ensure uniformity in the expansion. Then, the beaten gold alloy is carefully removed and put into second packets of skins which are beaten for about there hours.
     At this point, the gold is thin enough that the cutter can simply blow on it to move it. (More details here because I'm skipping some.) Basically, at this point there still remains 3-4 hours of beating with an 8-pound hammer, to get pieces that are 1/250,000 thick. After this process, the result is 3.0x3.3/8 inch squares of leaves in tissue paper books that contain 25 leaves.
     Here's a video that shows parts of the process.
Happy Holidays!


Saturday, December 21, 2013

A National Weather Service "Critical Weather Day" !! Winter Storm Gemini!

National weather service map for 12/22/2013. Significant colors are: pink in the midwest=winter storm warning. Blue surrounding the pink is winter weather advisory; bright blue up in east Minnesota=severe weather statement. Green to the east of this =flood warnings; rust color east of the green = flash flood warning; yellow = tornado watch. 
The news is full of weather alerts for the central and eastern U.S. and Christmas travel is already a problem in the eastern half of the U.S. The east is basking in spring-like warmth, while the midwest suffers from temperatures below average. We who live in the Pacific Northwest are experiencing mild conditions at the moment, but will get our turn next week when rain/snow return here.  The full National Weather Service report is here.
     Temperatures are in the 20's across Oklahoma (southwest end of the pink/blue area)  while, not all that far away, they are nearly 80 degrees across Mississippi (yellow rain pattern). A big frontal boundary separates these two regions. According to the NWS, the severe icing now occurring in Oklahoma-Missouri will transition to light and moderate snow tonight, and the ice threat shifts to lower Michigan and northern New England.  Flooding is a major concern in some areas where the rainfall is more typical of April and May than December. Melting snow will contribute to the flooding.
     And, as if this isn't enough, tornadoes and straight line winds will continue in the lower Mississippi valley and into the Ohio Valley, much further north than usual for this time of year. Here's a link to a 5:59 p.m. EST warning about the thunderstorms and tornadoes. If the prediction holds, storms will be affecting a broad range of the midwest and even over to Washington DC by Sunday night.
     In researching this, I discovered something new about the NWS. At about 8:30 a.m., the NWS Centers for Environmental Prediction declared a "Critical Weather Day" from their station in Milwaukee/Sullivan. In the affected area their offices are not to make any equipment of software changes that might affect the work flow, i.e., do nothing that will cause the system to fail in this critical time. It is also routinely put into effect during Presidential elections and inaugurations.
     Take care, friends and readers, if you are traveling the next few days!

Wednesday, December 18, 2013

Europa, emission from oxygen and hydrogen, and inferred jets of water

In the blue areas near the south pole of Europa, a satellite of Jupiter,
aural emissions from oxygen and hydrogen have been
detected by the Hubble Space Telescope. NASA image.
Just as we have aurora at the north pole because charged particles enter Earth's magnetic field, Europa has an aurora at its south pole because it is in the intense magnetic field of Jupiter. When atomic oxygen and hydrogen are excited by the magnetic field, they produce an aural glow that can be detected spectroscopically. The oxygen and hydrogen have been interpreted as being the products of water molecules torn apart by electrons along the magnetic field lines.
Top row: Images of the hemispheres
of Europa; other rows: combined images of
the hydrogen and oxygen emissions. This is
Figure 1 in the Science Express paper

The measurements were made from Hubble Space Telescope in December 2012, nearly a year before reported this week in Science Express and summarized in this NASA press release. The scientists involved (Lorenz Roth et al.) have stressed the need for caution because the Hubble Space Telescope was "pushed to its limits to see this very faint emission." Scientists are excited about this for two reasons. First, if confirmed, it would mean that Europa becomes the second moon spewing out water plumes (Enceladus is the other). Second, because there is good evidence that an ocean of liquid water exists under the surface of Europa, the plumes would be a way to sample its composition without having to drill through a thick crust. (The evidence for subsurface water is in the surface morphology and magnetometer measurements.)
     The plumes vary in intensity with the orbital position of Europa, but not in a way that is easily explained. They are active only when the moon is the farthest from Jupiter, instead of the more logical position closest to Jupiter.  The scientists postulate that the cracks that emit the water are closed when Europa is closest to Jupiter, and open when it is farthest away. The plumes extend up to about 125 miles altitude and the erupted "water" falls back onto the surface rather than escaping into space.  In the figure to the right, the detected "jets" in December 2012 are compared with 1999 and November 2012 images when the particles were not detected. In December 2012 the plume was near apocenter, and the other two times, close to pericenter, lending support to predictions of tidal modeling.

Wednesday, November 27, 2013

How do elk swim? I think he walked over a bridge! His name is "Bruiser."

The Whidbey Island male elk
Image credit: Sasha Castaneda Whidbey News Times here
OK, it's definitely a fluid dynamics problem to figure out how a lone elk can land our elk-less island. Don't get ants in your pants, this is not post about how humans got to Easter Island or about genetic evolution. It's just a story about one lonesome male elk.
     I live on an island. There are three ways to get here: (1) drive over a bridge; (2) take a ferry; or (3) swim. It's 100% unlikely that this moose did not ride a ferry to our island, probably not quite so certain that he walked over the bridge.
     So, the common assumption in our local media is that he swam. But, if that's true, why didn't he swim back during rutting season? My hypothesis below is that he's actually not a good swimmer, that he didn't get here by swimming, and that he walked here. If that's true or even likely, we should shoo him back over the bridge so that he can not be so lonely! Having worked in Yellowstone National Park for many years, I can attest that (a) bull elk are not happy during mating season, and (b) that they will great distances for you-know-what.
     Here's the story: This handsome guy appeared on Whidbey Island in September of 2012, and is the only elk on Whidbey. He is probably a healthy bull in a mainland herd that no longer tolerated him. The common pattern would have been for him to find new land with a few accompanying females and start a new herd. But, here is now, alone on Whidbey. But, one year later during rutting season, he's still here?  According to the Washington Department of Fish and Wildlife, "the animal decided to stay put." But, is that realistic? If Bruiser could get back to the land of bountious females, would he actually "decide" to stay put? Not a chance in my experience with elk.
    So, what is going on? A healthy male elk lives about 15 years in the wild, and can weaight up to a half-ton. Like Bruiser in the photo, they can sport great racks (which everyone on Whidbey hopes will NOT become a target of illegal hunting--beware: there' a great island-watch on this guy....) How far would he have to swim?Elk are strong swimmers, aided by hollow hairs that keep them buoyant. During mating season, they "buggle" a mating noise that carries very long distances. You can see videos of them swimming, but if you Google "elk swim distances", there's no world record for an elk swim. They can definitely ford rivers, but is it an "easy swim" from the mainland to Whidbey as the Washington Department of Fish and Wildlife is saying?
   At best, this guy started in a herd in Skagit Bay on the mainland as Fish and Wildlife believes, he would have swum 4-5 miles direct from the Skagit tributaries to here. Not likely? At the very best, he'd have wandered up to Deception Pass (by himself, without his mistresses?) to Deception Pass where he had a narrow passage, but harrowing waters. If he got that far, why not walk across the bridge? On those autumnal days when there are few tourists, long dark nights, why would an elk near the bridge not just take a walk? It would certainly explain why he can't find his way home! What if Bruiser's females are just out of reach on the other side?
     It's clearly a fluid dynamics problem (Aside: traffic flow is a fluid dynamics problem) to reunite Bruiser with his herd! It's also an environmental problem because the Skagit Valley herd of 1700 elk have been driving Skagit Valley (mainland) farmers crazy over decades eating their crops. Fertile male elk are being culled from the herd by Federal, state, and tribal hunters, and they are authorized to kill 15 at the moment. Maybe Bruiser is a very clever elk.

Monday, November 25, 2013

To storm or not on this Thanksgiving?

The GFS model forecast by the National Weather Service
for 4:00 p.m. Thursday PST
taken from Cliff Mass's blog discussed in text
Hmmmmm...who to believe? If you read CNN.com here, you get the impression that Thanksgiving is going to be a mess. In fact, that article is on the front page of CNN.com with titles "Massive storm for Thanksgiving" and "A side of weather with your story." I was feeling smug that I am staying local for Thanksgiving, and so I turned for a local forecast to my favorite northwest meteorologist Cliff Mass's blog, which is particularly funny today and, as usual, educational.
    And, what did I find?An essay on the "lack of storminess and ill-weather" in the Thanksgiving prediction! Cliff usually takes on the Seattle Times, but he missed a chance to take on CNN today! If you read the text of the CNN article, you can see that they are talking about yesterday, today and Tuesday mostly, not about Wednesday through Friday, but the headlines are certainly misleading.
        The only place on the mainland to see significant precipitation is far NW Washington State and, Cliff says, "not many folks live there and most of those watch Canadian TV. In other words, they don't count!" (The comments posted today reflects that he has a tolerant readership up in that area of Washington!) He really is in good form in this post. High pressure dominates most of the nation, there are no low pressure systems influencing the mainland (there is one noticeable one off the coast of southern California). He also points out that today (Nov. 25th) is the 6th straight day without rain in the Seattle area, when the normal chance of rain at this time of year is 65%. It looks like we could squeek by through Wednesday without rain, with some moving in on Thanksgiving. That would be 8 straight days without rain, and according to him, the chance of that is about 3%.
       But there's more to the story. According to the National Weather Service Weather Prediction Center, Wednesday could be messy in the midwest and east coast. Temperatures will be 10-20 degrees below average in the central east coast and upper midwest regions, and a front over the Great Lakes will produce lake effect snow over the Great Lakes through Wednesday (this does bring back memories of Thanksgiving storms where I grew up in Northwester Pennsylvania, where we got the lake effect snow from Lake Erie). A storm developing over the Central gulf coast will move toward this Great Lakes disturbance to produce moderate to heavy rain that will move from the central Gulf Coast into the Appalachians by Tuesday morning. This system of rain will then move east to the Mid-Atlantic on Tuesday and expand into Northern New England by Wednesday morning. Snow will expand into the Lower Great Lakes Tuesday evening and Wednesday. So, in detail, it's complicated and worth reading the various forecasts/news articles carefully.
        As, Cliff also pointed out, Thanksgiving and the first day of Chanukah coincide this year, the first time since 1888, and the next time may be 77,000 years from now! Compounded with the fact that Comet Ison will be the closest to the sun and brightest that same day, as Cliff says , "Happy Thanksgivukkah", or maybe better, "Happy IsThanksgivukkah!"

Sunday, November 10, 2013

Typhoon Haiyan may have killed 10,000. 3D structure of typhoons; Carnot engine theory

Boat in debris in Tacloban on November 10
Photo by Aaron Favila/AP from here
Although confirmed estimates of deaths due to Typhoon Haiyan remain around 1200, there are now credible speculations that there may be as many as 10,000 dead in just one village. My condolences to the people of the Philippines, and best wishes that supplies reach you quickly.
       According to this Reuters.com article, 70-80% of the structures in the path of the typhoon were destroyed. Most of the deaths appear to have been caused by a debris-laden storm surge that swept away whole villages. The capital of Leyte province, Tacloban, lies in a narrow cove where storm surges can be focused toward the city. The storm surge appears to have surged at least a half mile inland.
Tacloban location

November 9, 2013 Super Typhoon Haiyan imaged by NASA Astronaut Karen Nyberg on NASA's ISS.
The country was not unprepared for this event, and it is sobering that so much damage could still occur.  A question not often addressed is: Are there storms simply too strong for even modern engineering to provide safety?  The heartbreaking scenes from this storm are so similar to those of the tsunami damage from the 2011 Tohoku tsunami that it appears the answer may be "yes."  Could people have survived if all buildings had been made of concrete, and made so tall that people could take refuge above the 15' high storm surge reported? Can concrete buildings be designed to withstand 250 kilometer per hour (155 mph) winds?
       What determines the intensity of a tropical cyclone? Remember: typhoon, hurricane, cyclone are just different words for the same phenomenon.  Tropical intensity is usually measured by the value of the maximum wind speed.  Here's a table of cyclone wind speeds from The Guardian:
From TheGuardian.com November 9, 2013
Haiyan, although the strongest cyclone to make landfall is the fourth strongest in terms of measured wind speeds.
       Kerry Emanuel, Professor of Atmospheric Science at MIT, specializes in hurricane physics (see several references to his work at ** below). A tropical cyclone is driven principally by heat transfer from the ocean. They generally develop over water whose surface temperature exceeds 26 C. They occur in three main belts generally within 5 degrees latitude. The cyclones then move westward and poleward at speeds on the order of a few meters per second. Cold water kills them as can unfavorable atmospheric winds.
       Emanuel is famous for, amongst other things, his analysis of hurricanes as a Carnot heat engine. The Carnot cycle is a basic concept in thermodynamics. A thermodynamic cycle is the set of thermodynamic conditions (such as pressure, temperature, entropy, enthalpy) reached in a system as energy is transferred from warm to cool regions. In the process, some of the energy is converted to mechanical work.
The Carnot heat engine of Emmanuel
Taken from the Physics Today article referenced at **

In the cross-section diagram to the left, the horizontal axis shows distance from the center of a cyclone, and the vertical axis shows altitude. The colors, from deep blue to dark red represent entropy, with the cooler colors indicating lower entropy. Evaporating sea water transfers energy and entropy from sea to air, and this causes air to spiral inward from A to B.  As it moves, the temperature of the air is nearly constant (an isothermal process), its volume increases as it flows toward the low-pressure core of the cyclone, and its entropy increases. The air then rises rapidly upward (in the eyewall) and outward, from B to C, so rapidly that the process can be considered adiabatic and isentropic (note how the path B-C lies within the constant yellow color). Once away from the storm center at C, the air generally mixes with other storms and is lost from the system, but in idealized models, the air radiates in the infrared wavelengths into space, a process Emanuel considers nearly isothermal, and so it loses entropy. The air then sinks again (D-A) and warms through (nearly) adiabatic compression (in the deep blues of constant entropy). This closes the Carnot cycle.
       Emanuel then shows that the velocity of the surface winds is proportional to the difference in temperature between the ocean surface and the high-level outflow (conveniently, 100 C in the figure shown) and the thermodynamic disequilibrium between the ocean and atmosphere, E, which is the difference between the enthalpy of air near the surface and of air in contact with the ocean.  Using these concepts, Kerry then showed (in a 2003) paper, that a limit on maximum sustained wind speeds is about 85 m/s or 195 mph. (He did not comment on the possibility of higher winds as shown in the table above.) He also showed that the average cyclone dissipates about 3E12 watts, equal to the total electrical power consumption in the US in 2000, and that an exceptionally large storm can generate an order of magnitude more power.

**K. Emanuel, Tropical Cyclones, Annual Reviews of Earth and Planetary Sciences, 31, 75, 2003.
**K. Emanuel, Divine Wind: The History and Science of Hurricanes, Oxford U. Press, New York, 2005.
**K. Emanuel, Hurricanes: Tempests in a greenhouse, pp. 74-75, Physics Today, August 2006.