Monday, September 19, 2016
Sunday, August 14, 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.
Posted by Susan W. Kieffer at 4:24 PM
Monday, July 25, 2016
|The Roman Empire at its height, 117 A.D. From Huffington Post Oct. 12, 2015|
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.
Posted by Susan W. Kieffer at 1:01 PM
Sunday, May 22, 2016
|Sinabung as viewed from the east.|
Photo by Tom Casadevall, U.S.G.S., 1987
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
|Hoover Dam, photo by Mike Blake, Reuters|
Image from the article cited in text
Posted by Susan W. Kieffer at 9:57 AM
Monday, May 16, 2016
|Rickshaw drivers in rain in Dhaka. Image from CNN article referenced.|
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.
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:
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."
Posted by Susan W. Kieffer at 12:02 PM
Sunday, March 27, 2016
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 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.
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.
Posted by Susan W. Kieffer at 7:38 PM
Tuesday, January 19, 2016
|Dark spots attributed to dry ice along gullies in Lyell crater.|
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.
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.
Posted by Susan W. Kieffer at 2:00 PM
Monday, December 21, 2015
|Building after hit by landslide, from CNN.com here|
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.
Posted by Susan W. Kieffer at 12:55 AM
Tuesday, November 3, 2015
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!
Posted by Susan W. Kieffer at 12:47 PM
Friday, October 23, 2015
|Hurricane Patricia on Friday morning 10/23/2015, from Weather.com|
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.
Posted by Susan W. Kieffer at 12:48 PM
Wednesday, October 14, 2015
|Comparison of Jupiter's Red Spot|
with Earth. Image from
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%...."
Posted by Susan W. Kieffer at 4:45 PM
Saturday, August 15, 2015
|From National Park Service|
|From The Olympian|
Posted by Susan W. Kieffer at 1:42 PM
Friday, July 24, 2015
|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:
Posted by Susan W. Kieffer at 1:20 PM
Thursday, July 23, 2015
|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.
|Cover of Science in 2014|
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.
Posted by Susan W. Kieffer at 2:03 PM
Monday, July 20, 2015
|From this web site|
On the scale of future disasters in the Pacific Northwest, Kathyryn Schulz "The Really Big One," is eloquent, accurate, and incredibly readable:
And, a moving tribute to Claudia Alexandra, a prominent African American planetary scientist/engineer, who tragically died at age 56:
Posted by Susan W. Kieffer at 8:32 PM
Tuesday, July 14, 2015
|The last photo of Pluto for a bit, hopefully more soon.|
New Horizons' should reestablish contact with earth
Tuesday night (7/14/2015) and begin sending 10 years
worth of data back to earth, a process that will take 16 months.
"New Horizons' almost 10-year, three-billion-mile journey to closest approach at Pluto took about one minute less than predicted when the craft was launched in January 2006. The spacecraft threaded the needle through a 36 by 57 mile (60 by 90 kilometers) window in space--the equivalent of a commercial airliner arriving no more off target than the width of a tennis ball."
Pluto was discovered only 85 years ago by Clyde Tombaugh, an astronomer at the Lowell Observatory in Flagstaff. Tombaugh was doing a systematic search for a planet, dubbed "Planet X" at the time, beyond the orbit of Neptune. He would take photographs of the sky several nights apart and compare the images using a "blink comparator," an image that allowed rapid comparison of images. With this technique, astronomers can distinguish between stars, which do not move, and moving objects such as asteroids, comets and, in Tombaugh's case, a planet. It showed up very close to the place that Lowell had predicted.
|Kuiper Belt (blue dots). Attribution:|
WilyD at English Wikipedia
The yellow dot is the sun.
J,S,U,N are Jupiter, Saturn, Uranus, and Neptune.
Pluto resides in a region of the Solar System known as the Kuiper belt, shown in the image here. It was believed, until the 1990's, that Pluto was uniquely large and the Kuiper belt objects were unknown. Hence, Pluto was called a planet. The Kuiper belt was discovered in the 1990's, causing some to call Pluto's status as a planet into question, and with the discovery of Eris in 2005, a body 27% more massive than pluto, Pluto's status was sealed. The International Astronomical Union had to define the term "planet" for the first time because there was the possibility of "too many" planets!! To the dismay of some (many?) Pluto was demoted to a "dwarf planet" category.
So, what are the basics known or believed to be known at this point? The size of Pluto had been uncertain, and one result already from New Horizons is a new diameter--2370 km, up from an earlier value of 2302 km. This diameter is only about 2/3 of the diameter of the Moon. It's acceleration of gravity is 0.067 g, escape velocity is 1.23 km/s. The surface temperature varies between 33-55 K, with a mean of 44 K, truly a frigid planet. It's atmosphere consists of nitrogen, methane, and carbon monoxide at a maximum summer pressure of 0.30 Pa. The surface is 98% nitrogen ice. The color varies from black to dark orange to white--being similar to that of Io (the satellite of Jupiter that looks like a pizza).
Is there the possibility that tectonic or "volcanic/geyser" activity will be discovered on Pluto? The interior is believed to have a dense rocky core of approximately 1700 km diameter, and if radioactive heating is still significant today, it's been speculated that there could be a subsurface ocean 100-180 km thick at the core-mantle boundary. Here's a New Horizon's blurb that summarizes some of the facts and possibilities. We've been surprised before (Io, Triton, Enceladus) so here's hoping for some action!!
Go New Horizons Team, and thank you!!
Posted by Susan W. Kieffer at 2:01 PM
Monday, July 13, 2015
|A sun without any sunspots, photo taken on July 17, 2014|
Photo from here.
Here is the reference for the press release.
The sun's activity varies over a solar cycle of roughly 11 years (22 years if the polarity of sunspots is considered). To date, the cycle has been analyzed the phenomenon in terms of a dynamo driven by fluids convecting deep within the sun. A dynamo is a fluid dynamic condition of convection within a body that moves a convecting, rotating, and electrically charged fluid around within a body. Traditionally, solar physicists attempt to explain the measured properties of the sun and their variability with a single dynamo within the sun. We had a prolonged drought of sunspots over the past two years, but there are a few now and they emit strong enough particles to cause some concerns about telecommunications.
|Sun configuration on July 13, 2015|
From space weather.com
Valentina Zharkova is presenting a paper at the National Astronomy Meeting in Llandudno that proposes two dynamos: the traditional one deep in the sun, and another close to the surface. Each dynamo gives a periodicity of about 11 years, but they are slightly different and offset in time. The idea is that if they coincide appropriately, the effects will be large. The data are based on observations from 1976-2008. Running the model into the future, the model predicts that during Cycle 25, which peaks in 2022, and into cycle 26 (2030-2040) the waves due to the two dynamos will become exactly out of synch. This would result in a reduction in solar activity equivalent to the Maunder minimum of the 1600's, 370 years ago.
It will be interesting to follow this because the implications are enormous for global stability and economics. I recommend the great website space weather.com to follow solar events.
For a bit of prehistory, and my interest in the sun, my first published paper was a documentation of the evolution of sunspot groups, in the inaugural edition of a new journal Solar Physics: Zirin, Harold and Werner, Susan, Detailed analysis of flares, magnetic fields and activity in the sunspot group of Sept. 13-26, 1963, Solar Physics, 1, pp. 66-100, 1967,
Posted by Susan W. Kieffer at 8:48 PM
Thursday, June 25, 2015
|Jim Westphal (1930-2004)|
Posted by Susan W. Kieffer at 6:51 PM
Wednesday, June 10, 2015
|Scenary of the Wind River area illustrating that the|
surface is covered with sedimentary rocks and
supporting the observation that there is no
active volcanism within about 200 km. From the BBC
article by Matt Walker cited in the text.
The (very mathematical) analysis in this paper constrains the depth of the earthquake to 75 km (plus or minus 8 km), and makes it the second deepest earthquake now identified under a stable continental region. The depth of the Moho in this area is well constrained to be between 42-50 km, so the earthquake occurred well within the mantle, probably >20 km below the base of the crust. The only two other comparable earthquakes that the authors know of are the 1979 Randolphe, Utah, quake at 90 km, and the 2000 Arafura Sea earthquake at 61 km.
What caused this earthquake? The authors mention the possibility that the quake may result from the migration of fluids within the mantle. Such activity is known to cause microseismic activity at great depths in volcanic regions. However, the Wind River range is more than 200 km from the nearest volcanic region, the hot spot of Yellowstone. They also argue that since the Wind River earthquake ruptured an area of about 1,000,000 square meters, this area is much larger than would be expected from fluid-related origin. They cannot rule out this possibility, but prefer an explanation that the earthquake resulted from brittle fracture due to tectonically-derived stresses.
Posted by Susan W. Kieffer at 12:15 PM
Sunday, May 24, 2015
|The jet stream patterns that have set up the current|
wet situation in Texas. From Weather.com here
on May 24.
Lake Texoma is the 12th largest US Army Corps of Engineers lake, behind the Denison Dam on the Red River. It spans both Bryan County, Oklahoma, and Grayson County, Texas at the confluence of the Red and Washita Rivers. The dam site is 5 miles northwest of Denison, Texas. It is a popular lake, attracting about 6 million visitors per year. Water is pouring over the
|Lake Texoma Spillway the morning of Sunday,|
May 24. From TKKToday here. This is an excellent
site to see current and forecasted conditions as well
as helicopter footage of the flooding.
|U.S. Severe weather map as of 12:26 a.m. GMT (7:26 p.m.|
CDT) on May 25 from www.wunderground.com here
As the severe weather map shows, much of the central U.S. is experiencing severe weather in the form of flood warnings and watches, tornado warnings (red), and high wind advisories (blue and pale green near Chicago).
Saturday, April 25, 2015
|Location of earthquake and initial aftershocks|
Map added on 4/26 at bottom showing avalanche problems on Mount Everest.
A strong earthquake occurred in Nepal about 14 hours ago, and as I write this the death toll from the earthquake has risen to 1,457, with more deaths expected. The people face a cold night without shelter, water or electricity in many regions. The world's thoughts are focused on the people of Nepal with hopes that rescue efforts proceed smoothly an rapidly.
Max Wyss, Switzerland, runs a research program WAPMERR, in which he combines geographic data with seismic models to predict the injured and dead, with results sent to authorities and emergency people to aid in the planning of rescue and recovery (Note: you can subscribe to his service on the home page of WAPMERR). Unfortunately, his estimates are for 2000-10,000 fatalities, and 20,000-70,000 injuries. (Wyss's estimates have been updated to the numbers that I cite here just in the time it has taken to write this post, so check back with his site if you want updated information.)
According to the USGS, large earthquakes in this region have been relatively rare with only four events of M6 or larger known to have occurred within 250 km of this earthquake site. Two of these were a M6.9 earthquake in 1988, that caused about 1500 casualties and a M8.0 event in 1934 at roughly the same location of this 1988 event that severely damaged Katmandu and caused around 10,600 casualties.
|Image from Dave's Landslide Blog showing the|
location of the earthquake according to USGS model
Image from Blog as cited in the text
The Indian and Eurasian plates are converging at a rate of 45 mm/year, one of the fastest rates on the planet. This motion drives the uplift of the Himalayas. India is thrust under Eurasia, and the motion between the two plates makes this one of the seismically most hazardous regions in the world. The surface expression of the fault (along the red line in the figure below) in the vicinity of Nepal is marked by the east-west trending Himalaya Front in the north of India and Nepal sits within this belt. To the north is the high Plateau of Tibet. An excellent detailed summary of the regional tectonic setting is available on the USGS events page reporting the current earthquake found here.
|The tectonic boundary between the Indian plate (bottom)|
and Eurasian plate (top) with the red line showing
the surface location of the collision of these
two plates. USGS map as published today in USAToday.com
|The situation on Mount Everest as|
shown in NYTimes.com
News is trickling in that devastating avalanches have killed approximately 20 people on Mount Everest. Sadly, the best time to climb Mount Everest from a weather perspective is now, April and May. Sadly, on April 18, 2014, thirteen people were killed in an avalanche, at a site well known for its danger. There is a dangerous ice fall, known as the Khumbu Icefall, where seracs (unstable blocks of ice separated by cracks in an ice field) loom large over the route. Climbers usually try to pass quickly through here in the early morning before rising day temperatures amplify the hazard. According to Wiki, citing Russell Brice who runs a guide company called Himalayan Experience, ice falling from the serac narrowly missed climbers in 2012, and according to another mountaineer/writer, Jon Krakauer, the 2014 avalanche was triggered when a large block of ice broke off from the bulge. The Khumbu Icefall and the location of the 2014 avalanche are shown on the adjacent figure. It will be very interesting to see if the present large avalanche originated at the same site, but travelled much further all the way down the ice fall to cause so much damage in the Base Camp.
Remember that Nepal is landlocked. Tom Robinson of the University of Canterbury has done a preliminary analysis of the roads likely to be affected by landslides; that analysis is available on Dave's Landslide Blog here. The rescue situation w is dreadfully complicated with the airport closed and most access roads damaged by landslides. (Correction: The airport is open and India and China are flying in relief.) The monsoons are less than two months away, and since it is likely that many rivers are blocked by landslides, air and satellite photography of the landslide settings is essential to analyze future flooding due to blocked rivers.
Posted by Susan W. Kieffer at 1:31 PM