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


Wednesday, June 14, 2017

New coronal hole in the solar atmosphere, alert for aurora possibilities

Just saw a notice on Spaceweather.com that a large hole in the solar atmosphere is turning toward Earth. It is expected to blast us with a very high-velocity (700 km/second!!) stream of solar wind, arriving on June 16th, and possibly sparking G1-class geomagnetic storms. Could be interesting auroras particularly in the southern hemisphere because of the autumn darkness.

Friday, April 21, 2017

Spectacular video of a 400' wide waterfall in the Antarctic

There is a very well-written summary of two new papers in Nature in this weather.com article. Take a look at the video of the meltwater pouring off the surface of the ice sheet over a 400' wide waterfall. Scary!

Thursday, April 6, 2017

Planet Jupiter Opposition from sunset April 7 to sunrise on April 8, 2017

(No, there is not a video link to the left, but read on and you'll get one.) The following from NASA press release.

Tomorrow night, Jupiter makes its closest approach to Earth in 2017 so it'll be big and bright. This only happens every 13 months, and you can spend all night watching it, weather permitting. Opposition means that Jupiter will be opposite the sun so, as the sun sets in the west, Jupiter rises in the east. It'll be straight overhead at midnight, and will be near Spica, the brightest star in the constellation Virgo. And, if it's cloudy you can still catch nearly the same view for nearly a month after opposition.

So, what are those stripes across Jupiter? They are ammonia  (NH3) clouds in its upper atmosphere bounded by powerful winds like our own terrestrial jet stream. The dark bands are called "belts" and the light ones are called "zones." Gas rises in the light bands, and sinks down in the dark bands. The colors arise from slightly different temperatures and chemicals in the bands. Adjacent bands have winds in opposite directions. There is quite a bit of uncertainty about what actually gives the bands their colors (blue, orange, brown bands, and the "red" great spot (not visible in this photo). At the cool cloud temperatures, the chemicals in the atmosphere should be colorless, so some have suggested that hydrogen compounds tint the cloud tops.  Or, maybe there's sulfur.  The clouds do indicate the altitude of the clouds--blue is the lowest, red is the highest. The colors of the clouds are ever changing! There's a cool video of the belts and zones here.

Jupiter has 67 known moons! The four largest ones (Io, Europa, Ganymede, and Callisto) were first discovered by Galileo in 1610, and they are the first objects found in the Solar System to orbit another planet. They are called the Galilean satellites. Ganymede is the largest moon in the Solar System, bigger than the planet Mercury. Europa is the smallest, slightly smaller than our own Moon. It's got a smooth bright surface covered with ice, and perhaps liquid water 100 km deep. It's a favorite of the astrobiologists in their hunt for life elsewhere in the universe.  Callisto is the second largest of the Galilean satellites and is believed to be composed of about equal amounts of rock and ices. It's a candidate for a base for a human base if we ever get that far out and explore the Jupiter system because it's the furthest from the intense radiation of Jupiter. Finally, Io, the moon that looks like a pizza, is the most active moon in the solar system, with geysers and volcanoes erupting constantly to spew sulfurous compounds into its atmosphere and across its surface.

With a reasonable telescope, you'll be able to see these moons during the opposition!


Wednesday, March 22, 2017

Warm Gjulf Stream may portend energetic spring-time storms in the midwest

From Washington Post Capital Weather Gang on 3/22/17.
Weather in the Midwest is a fight between the receding Arctic cold air and the encrouching warm air from the Gulf of Mexico. The battle scars of this fight are the tornadoes of the Midwest. Today the Washingto Post summarized the current situation: "freakisly warm" waters in the Gulf of Mexico. Houston to Miami have had historically warm days (while we in the Pacific Northwest have had unusually cold and rainy times). Please see source in the figure caption for details and credits.
     The average sea surface temperature in the Gulf never fell below 73 degrees for the first time ever. Galvaston Texas broke 33 temperature records since November 1, and Houston had the warmest winter on record. Gads, I go there in a couple of weeks, and afternoon temperatures in Houston are projected to be in the 80's. Overnight temperatures have also remained high, a concern for health officials. Sea surface temperature in the Gulf is loosely correlated to tornado activity.  Additional requisites are: mixing layer with hot dry air at altitude that flows into the southern and central US to interact with this warm moist Gulf air. Another favorable ingredient is that there is a warm pool off the coast of Peru, and a cold pool of of the U.S. West coast, a pattern that correlates with high tornado activity.
    This report quotes: "A vigorous jet stream disturbance, originating from the Pacific Ocean, will crash into the southwestern United States around March 28. Once it enters the Plains around March 29 and March 30, it is likely to tap into the warm Gulf water and encounter the elevated mixed layer. Then severe storms may erupt." Not a great time to plan a cross-country trip, which is exactly what I've been doing! Will bring camera.....

Thursday, March 2, 2017

Origin of the Moon--redux!

Ever since Harold Urey proposed his theory for the origin of the Moon in 1952, it's origin has been the topic of debate, a debate that has not yet been settled.  One of the goals of the manned space program to the Moon was to get samples that would solve this debate but, because the Moon has undergone differentiation and a complicated geological history, we know a lot about the evolution of the Moon, but not about its origin.  In Nature Geoscience (v. 10, pp. 89-94, 2017) Rufu, Aharonson and Perets advance a theory that the Moon was formed, not by a single impact of a Mars-sized planetesimal as in the current paradigm, but by a series of smaller impacts.
     Some of the constraints that must be satisfied by a theory of origin are as follows.  The Moon is massive relative to its planet compared to Moons around other bodies in the Solar System.  The Earth-Moon system exhibits an unusually large amount of angular momentum. The Moon is depleted in volatile elements compared to carbonaceous chondrites which are taken as representative of undifferentiated planetary material.  This depletion is taken to indicate that some highly energetic process heated the moon. In contrast, rarefactory elements, such as Ca, Al, Ti, Ba, Sr,..., are enhanced. Iron is depleted relative to its abundance in the earth. The oxygen isotope compositions for the earth and Moon are similar, a fact that suggests that they were formed from the same material and their relative values compared to other bodies in the Solar System suggests that they were formed in the same vicinity.
     A major problem with single-impact scenarios is that a single impact cannot provide the observed angular momentum.  Rufu et al. argue that the largest impactor is also not necessarily the last one, and that multiple impacts are needed to provide both the observed angular momentum and observed mass. 
     Rufu et al. point out that computer simulations of impacts show that the projectile contributes more than 70% the the mass of the Earth-orbiting disk in which the ejecta land to later accrete into a single Moon. This so-called "skewed mass" contribution of the impactor is a problem because it is unlikely that the impactor and the proto-earth would have the same composition.  How can the Earth and Moon be isotopically similar in oxygen, titanium, tungsten?? In the multi-impact scenario proposed by these authors the proto-Earth experiences a number of collisions by bodies ranging in mass from 0.01 to 0.1 times the mass of the proto-Earth as shown in this figure from the paper:


Multi-impact scenario for
     Figure caption: Each impact by one of the small bodies generates a disk of material from which a small satellite forms.  These small satellites migrate outward under the influence of tidal interactions, and end up at their "Hill radii" to eventually coalesce to form the final Moon. The Hill radius for the Earth is the region in which the Earth dominates the attraction of satellites. 
    
Using computer simulations of multiple impacts in which parameters for the impactor mass ratio, speed, direction angle, and planetary rotation were varied, they examined whether or not the earth gained or lost material due to the impact. They found that lower impact angles favored planetary erosion over planetary accretion for the earth. They also found that it was difficult to make a Moon of the current mass from an impact, and that it was easier to create a number of sub-lunar mass disks sequentially, from which the Moon formed by the merger of multiple moonlets as shown in the figure.








    

Wednesday, December 14, 2016

Large Rogue Wave Detected by a Buoy

The Great Wave of Kanagawa by Katsushika Hokusai
One of the most popular chapters in my book "The Dynamics of Disaster" is the chapter on rogue waves. BBC.com reported that the World Meteorological Organization reported a 19-meter (62.3 ft) wave that occurred on Feb. 4, 2013. The wave was driven by 50.4 mph winds. It was, according to the WMO, higher than the previous record of 18.275 meeters (59.96 ft). Both of these waves were in the North Atlantic.
      (Contrary to popular belief, the Great Wave of Kanagawa pictured to the left is not a tsunami, but a rogue wave.)
     I don't know if it's the WMO or CNN, but the claims that these are record breaking waves recorded by buoys seems erroneous. As I discussed in my book, waves near to or greater than 100' in height were recorded from the 1990's onward as more and more instruments were deployed in the oceans.  One wave of 100.7 feet height, and the struggle of a fishing boat, the Andrea Gail, with these waves became the basis for "The Perfect Storm" by Sebastian Junger and a 2000 box hit movie by Warner Brothers.
    Although not recorded by a buoy, but by a laser on a drilling platform in the North Sea, the famous Draupner Wave reached a trough-to-crest height of 86 feet. On most days, waves around the Draupner platform on which the laser device was mounted averaged 10 feet. On that day, the so-called significant wave height was 36-40 feet. From statistics, the maximum height for these conditions would have been about 66 feet, so the 86' high wave was quite the exception.
     In 2000, the European Space Agency (ESA0 tried to quantify the frequency and size of rogue waves. Within a year of the start of the effort, two boats, the Bremen and the Caledonian Star, were hit by waves at least 100' in height, and over three weeks around this time, the satellites spoted ten waves higher than 80'. Waves up to 100 feet tall are most commonly found in the North Atlantic, North Pacific, and in the Pacific Ocean southwest of Australia and near Cape Horn. The average likelihood of encountering waves exceeding 36' in height along the main shipping routes in the North Atlantic is about 1%/day!

Monday, November 14, 2016

If you don't think that life can change in a second, dig this!

Cows stranded by earthquake/landslide New Zealand from NPR
AP wrote a story about these stranded cows and called it "Nowhere to Moove." At this time, it's not clear what the fate of these cows is/will be.
   I won't try to summarize the science of the November 14 New Zealand earthquake, but recommend Temblor by David Jacobson and Ross Stein. There were 2 deaths and a 6-8' high tsunami on the east coast of the South Island. The earthquake was about 60 miles north of Christchurch. Temblor reports that it was not one fault that ruptured, but four, including one that had not previously been recognized in Waipipi Bay. Displacement reached 33 feet. See the Temblor site for some spectacular pictures.

UPDATE on 11/15: Cows have been rescued!! 

Thursday, October 27, 2016

Bubbles in Beer, Dust in Air, and Why they Matter


I'm giving a talk this weekend at a meeting of the Jefferson Land Trust in Port Townsend. One of the points of the talk is that fluids of interest in geological processes can have some very unusual and unexpected properties. One example relates to the speed of sound in a liquid or gas.  The speed of sound in liquid water is about 1400 meters per second, basically a mile per second. That's fast compared to geological processes which typically have speeds less than a few hundred meters per second. But, if the liquid has gas bubbles, for example boiling water, the sound speed is dramatically depressed. Why? Consider first a simpler fluid than boiling water: beer. The sound speed (squared) is defined as the inverse of the compressibility*density.  Compressibility is "squishiness." Water isn't very squishy (as anyone who has done a belly flop off of a diving board knows), but if you add bubbles, things change (there's a reason that Olympic high-divers plunge into an aerated part of the pool). The density isn't affect much at all by the presence of small bubbles, but the squishiness is dramatically changed--the bubbly beer has almost got the squishiness of the bubbles. So, since the squishiness is in the denominator, the sound speed dramatically decreases--down to about 10 m/s. If the bubbles are steam in water, instead of air, there are other processes (condensation and evaporation of the steam as sound waves pass) the sound speed can be even lower, as low as 1 m/s. That means that if we walk at a pace of ~20 minutes per mile, and could walk through boiling water, we would be walking at Mach 2!!
     There's another situation in which low sound speeds can occur in geologic processes: dusty gases. The sound speed of a pure gas is inversely proportional to its molecular weight. The higher the molecular weight, the lower the sound speed: Helium ~ 970 m/s; Air ~340 m/s; Freon 12 ~150 m/s. I haven't done a lot of research on particle concentrations in dust storms, but in one study in Australia, concentrations of 10 mg/m3 for just the breathable particles were reported. If anyone wants to help convert this to mass fraction (mass ratio solids:vapor), help is welcomed!
     It is very difficult to determine particle loading in volcanic eruptions. Any sensors in the path of advancing gas/particle clouds are destroyed, but remote sensing techniques are improving.  The bottom line is that particle loading in destructive emissions are high compared to even desert dust storms, thus their destructiveness. These flows can be "internally supersonic," that is, supersonic inside themselves, but subsonic compared to atmospheric sound speeds (~340 m/s). Thus, they don't generate shock waves. The lateral blast at Mount St. Helens did not generate atmospheric shock waves. It did generate compression waves as the blast pushed on the atmosphere, and due to the complex structure of the atmosphere, these waves steepened into audible acoustic waves to the north, e.g., hear in Vancouver B.C.
     Bottom line: there are shocks and there are shocks. Some are inside these wierd geological flows, and others are in the domain of atmospheric sciences.

Tuesday, October 4, 2016

Anatomy of a hurricane

Added October 6: Here's a nice site to track the projected path of the hurricane.

Here's a nice graphic from AccuWeather on the anatomy of a hurricane showing conditions likely to occur in the four quadrants. There is speculation that this may be one of the rare hurricanes that loops around back on its earlier track, but the models are changing very rapidly.
     As Hurricane Matthew bears down on Haiti, it is worth reflecting on why Haiti seems to suffer so badly from hurricanes and floods. It may or may not see a disproportionately large number of hurricanes. Prior to 2008, only six major Category 3 or stronger hurricanes had struck Haiti since 1851. Cleo in 1964 killed 192 people; Flora in 1963 killed 8000. But in 2008, four storms (Fay, Gustav, Hanna and Ike) struck.
     However, given these storms, Haiti suffers a disproportionate amount of flooding (see Jeff Masters article here).  Charcoal from burnt trees had provided more than 85% of the energy in Haiti for decades and at present it's something like 60%.  This has resulted in denuded mountain slopes that cannot absorb and hold back the deluges of rainwater. For an interesting take (and references) on whether or not Haiti is as heavily deforested as popularly believed, or less so, see the interesting post in Envirosociety.org here.

Monday, September 19, 2016

Massive sinkhole in Florida

Just a short post to call attention to this spectacular and potentially dangerous sinkhole in Florida that is putting toxic water into an aquifer.

Sunday, August 14, 2016

Louisana floods of August, 2016

Photo from KOMONEWS.COM, Scott Sistek blog





Residing in Seattle, I know how much rain we get in the winter--southeastern Seattle got all of that rain in 48 hours from a stalled area of low pressure that tapped into tropical moisture. This post is largely a summary of Scott Sistek's blog post here.  Several thousand people have been rescued from flooded areas and the governor (who had to evacuate the Governor's Mansion in Baton Rouge) said that they "haven't been rescuing people. We've been rescuing subdivisions."
     The town of Lafayette in the wettest part of the storm reported 10.39" of rain on Friday, a record that toppled in one day when they reported 10.40" on Saturday. This combined total of 20.79" for two days is about what we get in Seattle in an average november+December+January+February (20.99"). The record had been 10.38" and it went from first place to third place in just two days! Baton Rouge had 16.71" in the same 48 hours. 
Radar showing estimated 20"+ in purple. From same source as above.
     The moisture was dragged moisture from the Gulf over the region as it drifted very slowly to the west. While these regions typically experience heavy rains, it is unusual for a storm to stall like this. When I looked at weather.com weather forecast, there is another week of rain and thunderstorms (though the rainfall amounts should be less) and 85-87 degree temperatures. 
     According to weather.com, the storm is heading north and will bring heavy rain into the midwest--St. Louis (5-8" there and in central-eastern Illinois), Indianapolis, Cincinnati, Columbus, Cleveland and northwestern Pennsylvania (1"). A number of weather systems are colliding--the stalled low pressure region, moisture heading north out of the Gulf of Mexico, and cool, dry air from Canada heading south.The same pattern is staying in place for a few days. Hot, humid, rainy conditions are also predicted for my University of Illinois friends in Champaign, IL, with a flash flood watch in place as I write this (Sunday afternoon). 
     I hope that all of those affected by this storm take care of themselves and others, and wish you a speedy recovery.

Monday, July 25, 2016

The Environmental Fall of the Roman Empire: Review of an article

The Roman Empire at its height, 117 A.D. From Huffington Post Oct. 12, 2015






In Daedalus, the Journal of the American Academy of Arts and Sciences, v. 145(2), pp. 101-112, Spring, 2016, I found an interesting article by Kyle Harper, a Historian and Professor of Classics and Letters at Univ. of Oklahoma, also Senior Vice President and Provost. The article is titled "The Environmental Fall of the Roman Empire." Since this publication isn't easily available, and I wanted to review the article, I'll summarize it here.

ALERT: I find this article very interesting, but also have some question about the facts, e.g., on p. 108 he refers to a "massive volcanic eruption in AD 169" for which I cannot find any documentation in the volcanology literature. In a reference (Sigl et al., Nature 523, p. 543-549, 2015, there is an "unattributed event" in AD 169.

The article begins with a description of festivites in 248 AD, the thousandth anniversary of Rome. The emperor at the time was Marcus Julius Philippus, "Philip the Arab," who hailed from the southern reaches of Syria. Harper's thesis is that these festivities hid the fact that Rome was already in decline and that, within the space of the next generation when Aurelius would be emperor, the decline was set in. Harper then comments that Gibbon's famous "Decline and Fall of the Roman Empire" of the late 18th century was written from the perspective of its time, when the role of environmental change was not thorougly explored. Data provided from ice cores, tree rings, marine deposits and cave minerals allow historians to reconstruct climate history on "civilizational time-scales with razor precision."
     Accumulated evidence suggests that Romans were short in stature, the average man standing 5'5" tall. Harper takes this as a measure that the resources that contribute to human health were already stressed. Human health is a function of both genes and the environment, the environment being critical to providing nutrition. The short stature, he hypothesizes, was due to a heavy burden of infectious disease that "drained their bodies' metabolic resources and stunted their growth." The environment, in this view, contributed to ill health (he discusses, but discards, Gibbon's thesis that the problems were either endogenous or exogenous but due to the "inevitable effect of immoderate greatness," i.e., overexpansion.
     Rome grew from a collection of small huts along the Tiber River rather slowly and fairly locally through many centuries until roughly the second century BC, e.g., as possibly defined by the Battle of Carthage in 149 BC. After the Romans razed Carthage, they controlled the Mediterranean, referring to it as mare nostrum, "our sea." The built an agrarian tributary empire that extended north to the 56th parallel down to the 24th parallel, from mid-latitudes to the edges of the tropics. This environment, particularly close to the Mediterranean, is a delicate and complex ecosystem, consisting of a patchwork of microclimates. The western territories are under the influence of Atlantic Ocean patterns, whereas the Eastern Mediterranean is influenced by this but also by other systems that influenced winter precipitation. Egypt, "the breadbasket of the Empire" was yet another climate regime. Movement of food over this huge area was expedited by the huge road system and control of shipping lanes in the Mediterranean. Malthus's "gigantic inevitable famine" hit the Romans only through times of relatively high prices. (Malthus, BTW, published just a decade after Gibbons.) Just as innovations in agricultural fertilization in the 20th century avoided the Malthusian consequences of soaring planetary population, trade and technological improvements forestalled limits on the productivity of land controlled by the Romans. And, just as we have been in a period of climate hospitality at present, there was a period called the "Roman climate optimum" in the late Holocene for the Mediterranean climate. Climate, commerce and technical progress allowed enormous population growth. Though, signs of stress were present in the short stature and low life expectancy (even by ancient standards). Summers were characterized by gastroenteric illnesses, autumns by malaria. "The Romans were rich, but sick."
     In the 160's A.D., smallpox struck, probably brought in along the trade routes from the Red Sea.It was the so-called Antonine Plague, perhaps the world's first pandemic.The benign climate that had blessed the Empire for a long time came to an end, perhaps with the mysterious AD 169 eruption that I mentioned above, but whatever the cause, for the next few centuries the climate began a descent into the "late antique little ice age." In AD 244 and 246, the Nile waters failed to rise. The price of wheat rose, and the food crisis in Egypt was felt throughout the Empire. One purpose of the millenium AD 248 games was to "ward off the evils of pestilence." The Plague of Cyprian (a bishop of Carthage who described the disease) ravaged the empire from AD249 for about 20 years. Alexandria, where it started, lost 62% of its urban population, 5000 corpses per day were wheeled out of Rome. Barbarians, who had previously been repelled rampaged, and the Empire started dissolving.The fabled Roman coinage collapsed and inflation ran rampant until gold was brought back as coinage. Later in the late third century, a very different empire arose.
     Harper concludes by pointing out that historians have mountains of new knowledge about ancient environments due to scientific advances. Earlier historians tried to explain the events of the first centuries AD without knowing the evidence about climate change and disease. "The proud urban people who cheered in the circus, or sang in the processions of the ludi saeculares in AD 248, could little have imagined that dynamic cycles in our proximate star, or the chance mutation of a virus in a far-off forest, would rattle the foundations of the familiar world they inhabited."...."an occasional and wary glimpse to the present?????

P.S. Note that there is also a literature on the role of lead poisoning, but it has become increasingly controversial, e.g., this article.

Sunday, May 22, 2016

Deadly Mount Sinabung eruption, May 21, 2016

Sinabung as viewed from the east.
Photo by Tom Casadevall, U.S.G.S., 1987
Mount Sinabung in the North Sumatra province of Indonesia, erupted on Saturday killing seven people in a village.  The village, Gembar, is one of four villages inside a 2.5 mile danger zone from which 5,000 residents were evacuated at the time. Villagers still enter the zone intermittently to tend to property. A video showing parts of the eruption and its ashy aftermath is available from The Guardian here.
     Sinabung is a highly active stratovolcano that rises to an elevation of 2460 meters. It is part of a subduction zone setting where the continental crust is >25 kilometers thick. The major products are andesite, basaltic andesite and dacite. There are four active craters at the summit. All four craters discharge sulfurous gases and form sulfur deposits which are mined by the local people.
    There are unconfirmed reports of an eruption in 1881, and solfataric activity was noted high on the volcano in 1912. It appeared to be dormant from this date until an explosive eruptions (VEI 2) in the summer of 2010. The eruption of August 27th was phreatic, with the initial emission of a grayish white plume followed by black plumes that reached 2000 m above the crater. The rocks and ash erupted came from altered rock in the crater and its deeper hydrothermal system.
    The events of 2010 were followed by a lava dome-forming eruption accompanied by explosive eruptions in September, 2013. Lava extrusion continued through 2014 at a rate of about 3.5 cubic meters per second, reaching about 0.1 cubic kilometer in volume. Sixteen people were killed in February 2014, and 30,000 local residents had to be evacuated. Magma mixing before the eruption is indicated by the presence of magic blobs and "plagioclase microlites more calcic than the phenocryst rims," and absence of a reaction rim on hornblende phenocrysts (Nakada et al., AGU abstract, 2014).
     As of the date of this post, the area remains under high alert and efforts are being made to evacuate any people in the danger zone.

Wednesday, May 18, 2016

A call for upgrading America's infrastructure and, in particular, aging dams

Hoover Dam, photo by Mike Blake, Reuters
Image from the article cited in text
I'm not going to summarize the article linked here, but having worked around dams, I truly believe the conclusions of this writer: major investment required to date infrastructure that dates back to the end of WWII, or even before.

Monday, May 16, 2016

Lightning strikes kill 65 people in four days

Rickshaw drivers in rain in Dhaka. Image from CNN article referenced.   


CNN reports that the number of people being killed by lightning strikes in Bangladesh has increased dramatically: last Thursday 34 died, 21 on Friday, 7 on Saturday and 3 on Sunday. Officials say that deforestation has "exacerbated the problem" with farmers working in open fields now where they are targets for lightning strikes. For comparison, five people have been killed so far this year in the U.S. despite our population being double that of Bangladesh.
     According to UCAR, there are more than 3 million lightning flashes worldwide per day. That equates to >30 flashes per second. The majority of lightning flashes are within clouds or between clouds. These outnumber cloud-to-ground strikes by about a factor of six in tropical storms, by a factor of two in midlatitudes. (I strongly recommend this UCAR link for well-explained snippets of interesting information about lightning!)
     What purpose does lightning serve on the earth? The earth's crust is negatively charged but the ionosphere (a layer in the atmosphere above 50 kilometers) is positively charged. The atmosphere between these two regions is slightly conductive which allows current to flow between these two regions. The earth-atmosphere potential "would disappear in a mere five minutes" were it not for lightning which, on a global scale, acts to separate charges on atoms.
NOAA image
     This mechanism overrides the fact that on the scale of a single thunderstorm, lightning releases electrical energy built up by the storm. Thunderstorms contain a lot of ice crystals and hailstones. Meteorologists believe, though the reasons are not well understood, that millions of collisions among these small solid particles cause the storms to evolve with a positive charge near their tops and a negative charge lower down. In a typical cloud-to-ground lightning strike, negative charge descends to the ground and the objects struck release a positive charge upward. The net effect keeps the charge of the earths crust negative.
    One of the more fascinating explanations on this page tells how a cloud-to-ground flash evolves. A series of "stepped leaders" move a bundle of charge a distance of only about one city block. Each step takes about a microsecond, followed by a pause of about 50 microseconds, and then another step.  At each step, the evolving bolt may change direction toward a stronger electric field area, resulting in a final flash that is full of zigs and zags. On the ground, there may be several regions of opposite charge, causing the bolt to split into several branches as it nears the ground. Just before reaching the ground, the leading step induces an electric potential of some 10 million volts. This is sufficient to bring up surges of positive charge from sharp objects or irregularities near the ground. Once the negative tip of the bolt and the rising surge of positive charges meet, typically a few tens of meters above the ground, the connection between the cloud and ground is established. The return stroke "zips upward at a rate much faster than the stepped leaders descent." It is this return stroke that produces the visible flash.  Air surrounding the bolt is heated to about 30,000 C (54,000 F), creating the shock wave that we register as thunder.
     Finally, I can't do better than to print the whole UCAR instruction on how to avoid being struck by lightning:

"How can I avoid being struck by lightning?

Going indoors during a thunderstorm is by far the best way to avoid lightning. New guidelines recommend taking shelter as soon as you notice thunder arriving less than 30 seconds after a lightning flash. Since it takes five seconds for thunder to travel one mile, the 30-second interval means a flash is less than six miles away. This, in turn, means that the next flash might strike your area soon. Outdoor activities such as baseball or football games should be interrupted for shelter as soon as the 30-second rule is met. (An entire football team of 11 players was killed by a lightning strike in Africa in the fall of 1998.)
Shelter is not failsafe. Lightning can strike though telephones, except for the cellular variety. You should avoid taking showers or standing by windows, screen doors, or patios. To protect household appliances, unplug them before (but not during!) electrical storms.
Outdoors, the idea is to avoid being near--or being--the highest object around. Get away from isolated trees, metal fences, wire clotheslines, and the like, and avoid standing in an exposed area or near water. If you are the tallest thing around, or in a boat on open water, crouch down to reduce your height (but don't lie flat). Lay down metal sports equipment and dismount bicycles. Take especially swift action if your hair stands on end, as that means charged particles are starting to use your body as a pathway. The safest form of vehicle is one with a fully enclosed, all-metal body, which helps to channel electricity around the interior. Make sure the car's windows and doors are completely closed.
Finally, remember that lightning can, and often does, strike the same spot more than once--even the same person. U.S. park ranger Roy Sullivan reportedly was struck seven times between 1942 and 1977."


Sunday, March 27, 2016

New model for the Ries impact crater, Germany

I haven't worked much on meteorite impact craters for about 20 years, and have been delighted to find how much the concepts have changed since Chuck Simonds and I published our ideas about the role of volatiles and lithology in impacts back in 1980. The dramatic increase in our understanding results from two factors: over a half century of detailed work by (mostly) German geologists documenting the Ries in detail at all scales, and the dramatic increase in computational capacity since the 1980's. I reproduce here a figure from Stoffler et al. (2013) and a brief description of the five phases of an impact that they discuss. Strongly recommend the original papers. The impact scenario is for formation of the 24-kilometer Ries Crater in Germany, about 14.5 million years ago.  It's a favorite spot for meteorite enthusiasts, not the least because in the village of Nordlingen, a church is constructed from one of the impact products, suevite!


·      Phase 1, panel a: Impact phase, about 2 milliseconds after impact;
·      Phase 2, panel b: Primary ejecta plume and final shape of the transient cavity; ejecta curtain and clast-laden impact melt layer, about 10 seconds after impact;
·      Phase 3, panel c: fully developed primary ejecta plume, crater shape after collapse of transient cavity; formation of central uplift, and innermost ejecta blanket, the Bunte Breccia from deposition by the ejecta curtaint; about 40 seconds after impact, and
     Phase 3, panel d: buoyant primary ejecta plume begins collapsing,  deposition of Bunte     Breccia; slumping of volatile-containing sediments into the hot melt pool begins; about 2 minutes after impact
·      Phase 4, panel e: Secondary plume(s) formed by reaction of the hot melt pool with water for a fuel-coolant-interaction (FCI) process is fully developed, time = days to months;
·      Phase 4, panel f: Collapse of the FCI-induced secondary plume(s) and early phase deposition of outer suevite and part of crater suevite. Time = minutes to tens of minutes after start of FCI
·      Phase 4, panel g: late phase of secondary plume(s) and deposition of the main mass of crater suevite-time scale of months to years
·      Phase 5, panel h: final crater with all units in place, before formation of a crater lake if that happens. Time – months to years after impact.


References:


    Kieffer,  S. and Simonds, C., The role of volatiles and lithology in the impact cratering process, Reviews of Geophysics and Space Physics, 18(1), 143-181, 1980.

    Stoffler, D., et al., Ries crater and suevite revisited--Observations and modeling Part I: Observations, Meteoritics and Planetary Science 48 (4), 515-589, 2013.

    Artemieva, N.A., Ries crater and suevite revisited--Observations and modeling Part II: Modeling, Meteoritics and Planetary Science 48(4), 590-627, 2013.





Tuesday, January 19, 2016

Gullies and debris flows on Mars: Liquid water or dry ice phenomena???

Dark spots attributed to dry ice along gullies in Lyell crater.
In the January 2016 issue of Nature Geoscience, there is one paper and one News and Views commentary that take on the currently popular idea that gullies and debris flows on Mars are caused by liquid water. These two papers advocate a major role for dry ice, CO2. (Unfortunately, neither article references an important paper by Troy Shinbrot and colleagues in 2004 in which the title says a lot: "Dry granular flows can generate surface features resembling those seen in Martian gullies," PNAS, 101(23), 5 pages. This model appears relevant to the mechanism in part (b) of the cartoon below.)
      The commentary by Colin Dundas (Nature Geoscience 9, pp. 10-11, 2016) sets the stage by summarizing the context. Although the gullies look like terrestrial landforms caused by running water, there is a real problem finding the source of the putative water. Groundwater discharge is frequently cited, but this is inconsistent with the occurrence of gullies on sand dunes and isolated peaks. "Whatever the water source, wet models imply the repeated occurrence of thousands of cubic meters of liquid water at each gully, which would have profound implications for both climate and possible biology on Mars." Over the past two decades photographs of the surface have documented channel erosion and the deposition of debris flows in locations where the present climate is too cold for substantial liquid water. However, many (most?) of these locations occur where seasonal CO2 frost occurs, and gully activity occurs mainly in the winter and spring when CO2 frost is observed on the slopes and is available for participating in gully formation.
    
      In the major article, Pilorget and Forget (Nature Geoscience, 9, 65-69, 2016) develop the model with numerical simulations. Referring to the second figure here, the model is as follows: (a) At the end of winter, the H2O-ice cemented soil (dark blue) is overlain by a regolith and a mantle of CO2 ice (light blue) that is ~1 m thick at the poles and thinner toward mid-latitudes. As the solar intensity increases solar rays penetrate through the CO2 ice and are absorbed by the regolith. This leads to a pressure and temperature increase in the regolith, and the formation of CO2 ice in the pores (light blue circles) of the regolith. (b) When the pressure in the regolith reaches and slightly exceeds the cryostatic pressure of the CO2 ice layer, it rises and cracks, releasing the pressurized CO2. Any remaining CO2 ice in the pores quickly sublimates, and the now-mostly-dry regolith destabilizes and flows out forming viscous granular debris flows because the cryostatic pressure is sufficient to mobilize the grains. (c) Flow of the material thins the regolith, destabilizing the H2O ice underneath and it loses the H2O through sublimation. (d) The process results in the local ice table moving deeper into the crust and the formation of incisions that become, or enhance the formation of, gullies.
     The model used is one-dimensional and examines the evolution of a column that consists of a regolith underlying a CO2 ice layer and an atmosphere. The atmosphere is in radiative-convective equilibrium and the incident radiation on slopes of varying angles is computed. In the CO2 ice layer and the regolith, heat conduction and radiative transfer through the ice are calculated, as well as diffusion, condensation and sublimation of CO2 and the latent heat exchanges (all described in the Methods section). CO2 is predicted to condense above 50 degrees latitude on flat surfaces and down to ~30 degrees latitude on pole-facing slopes.  In such locations, subsurface H2O-ice in equilibrium with the atmospheric water vapor is expected to be present below a layer of dry regolith ranging up to several centimeters thickness. This justified treating the model regolith as a dry porous layer lying above an impermeable, ice-cemented soil.




Monday, December 21, 2015

Horrific landslide slams industrial park in Shenzhen, China

Building after hit by landslide, from CNN.com here        

On Sunday, noon local time, a landslide (mudflow?) slammed into an industrial park burying, according to recent CNN reports, 22 buildings according to the CNN report, 33 buildings according to a NYTimes.com report. The site appears to be fairly close to Hong Kong on the north side, and in an area of steep hills. Accounts are obviously very preliminary at this time. Three buildings housed workers. 1500 rescue workers are on site combing through rubble. A section of a major pipeline carrying natural gas exploded when hit by the slide. A video of one building collapsing is available here (from CNN.com), but it doesn't show anything of the slide/flow itself.  I will update this if more information becomes available, and I recommend keeping an eye out for a post on AGU's Landslide Blog. Dave Petley hasn't posted anything as of the time I'm writing (approximately midnight, US west coast time), but he will likely have a thorough report in the near future.

The Twitter account of the official People's Daily, citing the Ministry of Land and Resources, reports that the material that flowed was a huge pile of construction debris.

Tuesday, November 3, 2015

Great meteor fireball over Bangkok

From BBC.
I don't know if the link below will work, but if it does, it's a great video of a meteor in the sky over Bangkok. I've never seen a fireball trail that "bursts" several times as this one does. In the image at the left, the thin tail in the upper right is the remnant of at the first burst at high altitude, the center one is stye second, and the left one is just appearing. The meteor appears to have burned up shortly after the third burst appears. Easier to see on the video than to describe!

http://www.bbc.com

If the link doesn't work, Google "Fireball meteor lights up Bangkok skies" on BBC.com.

I guess that I should speculate on what is causing this (though I suspect that there's a literature out there somewhere that I can't find.)  As the meteor enters the atmosphere, friction causes it to heat up and glow brighter and brighter.  If the part of the crust that is heated spalls off, it would perhaps cause the rapid brightening burst as well as expose a cold interior. That cold interior is then exposed to the atmosphere, friction heats it up, and it spalls off again to form the second burst.  The cold nucleus then heats up to form the third, and final, burst.

Rule of thumb is that "shooting stars" are about the size of a pea. So, maybe this meteor that caused the triple burst was the size of a....golf ball?? Input welcome!

Friday, October 23, 2015

Hurricane Patricia --Category 5 aiming for Mexico

Hurricane Patricia on Friday morning 10/23/2015, from Weather.com

As I write this, Hurricane Patricia is less than 100 miles off shore of Mexico, aiming for landfall south of Puerto Vallarta and north of Manzanillo.  Evacuations have been underway. Mexico's second largest city Guadalajara lies inland fortunately south of the projected path that will take it into southern Texas. It is expected to make landfall Friday afternoon or evening, and to fizzle out near Monterrey on Sunday.
     Patricia is a Category 5 with sustained winds of 200 miles per hour in a small area about 15 miles across near the center. For comparison, the definition of a Category 5 hurricane is one with sustained winds of 157 miles per hour, so Patricia is a strong Category 5. Individual gusts can reach strengths of 50% greater than sustained winds**, implying gusts of 300 mph or 133 meters per second.  Since the speed of sound in air is ~340 meters per second, these winds have a Mach number of nearly 0.4! Mike Smith of Accuweather has drawn the analogy that Patricia is like a 15-20 mile wide EF-4 to EF-5 tornado. Since a mile-diameter tornado is huge, this gives a feel for the size of the dangerous region of this hurricane.
     Patricia has taken the record for the lowest pressure in any hurricane ever recorded with a pressure in the eye of 880 millibars. Hurricane Wilma set the record at 882 millibars ten years ago. Patricia is the strongest hurricane ever recorded in the eastern Pacific. Rainfall amounts of 8-12" are projected with isolated instances of 20". Wave heights near shore have increased already and a dangerous storm surge is expected at the landfall site. Fortunately the inland terrain is mountainous and shear between the storm and the mountains will cause the hurricane to weaken within about 36 ours.
     Category 5 storms tend to cluster into El Nino years because warmer sea surface temperatures and reduced wind shear favor their formation, though there are exceptions.  Since this is the year of the so-called "Godzilla' El Nino, it'll be interesting to follow this season.

     For comparison, here's a link to a post that I did on Super Typhoon Haiyan two years ago, and here's a link to a list of Category 5 Pacific hurricanes.
________________________
 
**Landsea, Christopher W. "Tropical Cyclone FAQ Subject: D4) What does "maximum sustained wind" mean? How does it relate to gusts in tropical cyclones?"Atlantic Oceanographic and Meteorological Laboratory. National Oceanic and Atmospheric Administration. Retrieved 2006-03-16.

Various weather sites, however, are projecting maximum winds of the order of 250 miles per hour.

Wednesday, October 14, 2015

Jupiter's Red Spot is shrinking!!

Comparison of Jupiter's Red Spot
with Earth. Image from
http://startswithabang.com/?p=1553
After a 2-month hiatus, I'm going to work my way back into regular posting. But will start in a very lazy way by referring you to a really cool video here, a new NASA time-lapse portrait of Jupiter!
      Jupiter is the largest planet in the Solar System with an equatorial radius of about 11 times that of the Earth, and about 1/10 of the radius of the sun.  It is a gassy planet, and it's upper atmosphere consists of about 75% hydrogen and 24% helium by mass, with a trace of methane, water, ammonia, .... It's atmosphere spans 5,000 km (3100 miles) in altitude, though since Jupiter has no solid surface of rocks like the earth, the base is rather arbitrarily defined as the point where atmospheric pressure is about 10 times the surface pressure on Earth.
     The Great Red Spot is a vortex, an anticyclonic (rotating counterclockwise) storm that is known to have existed since 1831, and possibly since 1665 where it was reported in the very first volume of the Philosophical Transactions (of England)  that a small spot in the biggest of the three observed belts had been spotted with a twelve foot telescope. The Great Red Spot is about three times the diameter of the earth as shown in the image to the left. It "sticks out" above the surrounding cloud tops by 8 kilometers.
      For a technical paper on the topic, see Asay-Davis et al., Icarus, 203(1), pp. 164-188, September 2009, in which they show that "between 1996 and 2006, the area circumscribed by the high-speed collar of the Great Red Spot (GRS) shrunk by 15%...."


Saturday, August 15, 2015

Glacial outburst floods at Mount Rainier

From National Park Service
A glacial outburst flood is a large sudden release of water from a glacier. These are common in Iceland where they are known as Jokulhlaups (o with an umlaut that I can't do in a blog). Here is a link to an impressive video of one in 2010 during the active phase of Eyjafjallajokull.

From The Olympian
On Thursday afternoon, August 14, about a half acre of the South Tahoma Glacier on Mount Rainier broke off, triggering a series of outburst floods. The Rainier outbursts were very very small by Icelandic standards, but at least one was fortunately captured on video. A park volunteer heard a "loud roaring sound, followed by the sounds of water moving boulders and the cracks of breaking trees." Fortunately, that volunteer and another nearby were able to get to high ground, from which they observed the outburst stages. Debris flows were reported at 9:40 a.m., 10:30 a.m., 11:30 a.m., and 12:40 p.m. The 11:30 event generated a debris flow that reached the Westside Road at noon. The road was sufficiently damaged that it will be closed for the weekend. In total, seven waves of debris were recorded.  The debris ended up in Tahoma Creek valley. The Nisqually River saw a 0.5 foot rise during the afternoon. Since 1980 more than 30 debris flows have been recorded from the South Tahoma Glacier. Hot dry weather and/or heavy rainfall trigger the events.

Friday, July 24, 2015

#PacificWarmBlobMustDie--a fun article by Scott Sistek on our warm and dry Northwest

Photo from Scott Sistek article
July 23, 2015 Komonews.com

I don't usually just reference a news article, but this one today by Scott Sistek in KOMONEWS.COM is a great read, and explains the # in the title of this post:

http://www.komonews.com/weather/blogs/scott/Why-has-it-been-so-warm-so-long-This-picture-says-1000-words-318245281.html




Thursday, July 23, 2015

Kepler spots potentially habitable planet like our Earth

Temperature of the Earth under present
conditions with a solar flux of 341 W/m2,
and just before the runaway greenhouse is triggered
for a mean solar flux of 375 W/m2.
From the Leconte et al. article referenced in text.
NASA has just released an announcement this morning that the Kepler spacecraft has spotted a planet about 60% bigger than our Earth in a habitable zone of a star "similar to our sun."  The planet is dubbed Kepler-452b, and it's about 1400 light years from Earth in the constellation Cygnus. It's gravity would be about twice that of the Earth's. The star around which it orbits is a G2-type star like our sun, has the same temperature, is 20% brighter, and has a diameter about 10% larger.
Cover of Science in 2014
     Aside: Todays announcement is  a bit confusing because a year ago the Kepler team had the cover photo and a report in Science (v. 344, no. 6181, pp. 277-280, 2014) titled "An Earth-Sized Planet in the Habitable Zone of a Cool Star." This star has a radius of about 1/2 that of our sun, but the planet, Kepler 186f, is in the habitable zone and could support liquid water if it has an earth-like atmosphere and water at the surface. It appears that the difference between these two announcements is that the star around which Kepler-452b orbits is more similar to our sun than the Kepler 186f star.

      In 2013, Sid Perkins wrote a piece in Nature (December 11, 2013) discussing the habitable zone and summarizing the work of Jeremy Leconte at the Pierre Simon Laplace Institute in Paris (Leconte et al., Nature, 504, 268, 2013).  Leconte ran the first fully three dimensional model of hot, very moist planetary atmospheres (and thus the work only applies to planets that have abundant water like the Earth; there is no evidence yet whether the newly discovered planet in Cygnus has water). Previous models had been one-dimensional and considered only how the atmospheric conditions changed in the vertical direction, ignoring horizontal transport effects, whereas this model can take account of the Hadley circulation. Leconte et al. conclude that the runaway greenhouse will take effect at a mean solar insolation of about 375 W/m2. In this model, warming of the planet causes the formation of cirrus clouds at high altitudes. Such clouds trap heat, and the heating leads to more evaporation, which leads to more clouds and thus the feedback to a greenhouse effect. The model also suggests that the large-scale circulation (not possible in 1-D models) creates cloud-free areas in the mid-latitudes that allow heat to radiate back to space. The conclusion is that the inner edge of the Solar System's habitable zone is about 142 million kilometers from the sun.  Earth is at 149,600,000 kilometers so we are close to the inner edge of the habitable zone. Other authors, however, have concluded that the inner boundary could be considerably closer especially for planets that have much less water to feed the greenhouse effect (Petigura, et. al., Proc. Natl. Acad. Sci. USA 110, 19723, 2013).
     Wiki has a good summary of habitable zone thermodynamics here.

Monday, July 20, 2015

Recommended Readings!

From this web site
I don't usually post reviews or recommended readings, but at the behest of a couple of valued readers, here are two that are highly recommended:

On the scale of future disasters in the Pacific Northwest, Kathyryn Schulz "The Really Big One," is eloquent, accurate, and incredibly readable:

http://www.newyorker.com/magazine/2015/07/20/the-really-big-one

And, a moving tribute to Claudia Alexandra, a prominent African American planetary scientist/engineer, who tragically died at age 56:


http://www.latimes.com/local/obituaries/la-me-0719-claudia-alexander-20150718-story.html