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

Saturday, June 29, 2013

What's up with the weather in the Pacific Northwest?

500 hPa contours for Monday, 5:00 p.m.
From Cliff Mass blog referenced in text
Note the N-S alignment of the contours
as discussed in the text. The low is the red
area offshore of the northwest; the high
is the blue region centered over Idaho. This
system has been migrating from east to west
over the past week.
    CliffMass.blogspot.com" and again refer you to it regarding the nation's weather--particularly the weather in the Northwest. Mass is a professor at the University of Washington in Seattle; here is his home page. His posts of Wednesday and Friday, June 26-28, discuss the upcoming heat wave in detail. Note: this heat wave follows a cold and wet spring, and is only a week before the infamous July 4 date when "summer comes to the Northwest."
 I have several times referred to one of my favorite blogs "
     Briefly, the whole west coast is heating up, with the highest temperatures off the coast in the interiors of Washington and Oregon, with somewhat lower, but still high temperatures, in eastern California and western Nevada (Death Valley could be interesting). Last week (which was wet and cool here) there was a VERY deep low (italicization same as Mass) over the eastern Pacific, and a high-pressure ridge over the Rockies and western Plains. This setup (at the 500 hPa height) allowed moist air to flow in from the southwest. Yesterday (Friday) the low center and the high pressure ridge moved westward, the high-pressure ridge intensified, and the Northwest dried out. By Monday, the high pressure will intensify and will be located west of the Rockies. The low and high regions are getting "squashed" from east to west, aligning the pressure contours in a north-south configuration. Since the winds follow the contours, warm air will flow into the Northwest from the south. This pattern will continue into Tuesday, bringing dry hot air up from the south into the Northwest. The highest temperatures will be east of the Cascades, but they will not be record breaking. To have new records in western Washington, the ridge would have to be further westward than it currently is, essentially sitting on top of Seattle. Mass predicts that on Monday there is a chance of a record high at SeaTac airport; the current high for that date is 87 F.
CAPE index for Monday and Tuesday
From the Cliff Mass blog referenced in the text
     I have now moved to the Northwest from the Midwest, thinking that I left thunderstorms behind me. WRONG! In a very unusual situation for the Northwest, it is possible that there could be some severe thunderstorms in the region, largely along the Cascades in Oregon. There is a measure of thunderstorm potential called CAPE (Convective Available Potential Energy). Typical high values of the CAPE are a few hundred in this region; it is projected to reach 2500-3000 Monday and Tuesday. However, countering the tendency for massive convection that would cause thunderstorms, is a sinking motion of the high pressure ridge and a lack of strong upward convective motion that would release the energy. Mass says, however, that "the models would not have to be very wrong for something very interesting and very severe to happen. Need to watch this."

Friday, June 14, 2013

The Great Pacific Garbage Patch and ??The Great Lakes Garbage Patches???

Add caption
NOAA has, over the past few years, made a rather big deal of a stagnant zone in the East Pacific Ocean where garbage, including plastics, are accumulating. For example, on the left is a photo from the NOAA Marine Debris Program showing garbage (though this garbage is on a beach, not in the Pacific), including "microplastics", plastic pieces less than 5 mm long. Plastics in the ocean do not fully degrade, but weather into smaller and smaller pieces. These, in turn, are dangerous to marine life. Here is an excellent summary and fact-file related to this problem.

Several myths have grown up about the "garbage patch," worth clarifying here:

(1) It's not really a "garbage patch," e.g., a floating landfill. Rather, the debris consists mostly of small bits of plastic suspended throughout the water column. A good analogy is that it is more like flecks of pepper floating throughout a bowl of soup, than a skim of fat that sits on the surface. There are three major garbage patches stretching to the west from the coast of southern California and Baja: the Eastern Garbage Patch, the Western Garbage Patch out near the Kuroshio current, and, further north between these two, a subtropical convergence zone.
Graphic is from Tomczak, M., and Godfrey, J.S., 2002,
Regional Oceanography: an Introduction, online version.
A is a convergence zone; E is a coastal upwelling
divergence zone. Black arrows are winds; green arrows
indicate water movement. This graphic from
this WWW site
        (2) There is not just one, but many garbage patches. They form at "convergence zones" in the ocean. A convergence zone is a place where water, and plastic, accumulate in the center of rotating winds. An example is shown in the graphic to the right.  When there is a high pressure weather system in the North Pacific, air moves from high pressure to low pressure, deviation continuously to the right because of the Coriolis Force, which causes the wind to blow in a clockwise circle around high-pressure weather systems. The water curls to the right of the wind. Together they create a zone of convergence in the center, A in the graphic. As new water is brought into the system by the winds, water that was there sinks. However, the plastic doesn't sink with it and gets left behind, accumulating in the upper part of the water column. The process works in reverse in the adjacent low pressure system--water diverges away from the rotating winds. Plastic accumulates in the convergence zones.
     In an interesting post on May 16 by the NOAA Office of Response and Restoration, the question "Is there a garbage patch in the Great Lakes?" is asked. In an understatement, NOAA points out that "The Great Lakes are no mere group of puddles. They contain nearly 20% of the world's surface freshwater and have a coastline longer than the East Coast of the United States."
Average summer water circulation in the Great Lakes.
From Beletsky et al., 1999 as posted by NOAA here.

In the Great Lakes system, water flows from the big Lakes Superior and Michigan in the west into Lake Huron, through Lake St. Clair (not shown**) and the Detroit River into Lake Erie. It exits through Niagara Falls and Lake Ontario into the Saint Lawrence River and then out to the Atlantic Ocean. Within each Lake, the "current" breaks down into numerous eddies (convergence zones similar to those discussed above) whose geometry is determined by the elevation differences (highest in the west, lowest in the east), the geometry of the Lake beds, wind, solar energy, differences in density in the water column due mostly to the temperature differences, and the shorelines. There is now a project based at the University of Waterloo in Canada, partnered with COM DEV (a designer and manufacturer of space and remote sensing technology) to develop and test remote sensing methods for detecting plastics in the Great Lakes. Here's Sarah Opfer's blog on this topic for more information.

**Lake St. Claire is the small nearly-circular feature shown on this map between Lake Huron and Lake Erie.

Wednesday, June 5, 2013

A "shocking" start for life on Earth?

A schematic of the synthesis of nonbiological hydrocarbons
during impact of simple icy comets on the early Earth
Image from DOE/Lawrence Livermore National Laboratory
as published in ScienceDaily.com 
ScienceDaily.com has reported on a paper in press for the  January 20, 2013 Journal of Physical Chemistry A. The authors are from Lawrence Livermore Berkeley Laboratory (LLBL) (Nir Goldman) and the University of Ontario Institute of Technology (Isaac Tamblyn, who is a former LLNL postdoc). The exciting conclusion of the work is that it is possible that during the short duration of a comet impact, shock waves could have provided the necessary conditions (pressure and temperature) and energy (heat) to allow chemical reactions that would have produced prebiotic hydrocarbons such as nitrogen-containing heterocycles. These are believed to be the prebiotic precursors to DNA and RNA base pairs.
The structure of pyridine, C5H5N
Wiki image by Calvero
       What are "nitrogen-containing heterocycles"? A heterocyclic compound is a ring-structured compound, with the "hetero-" meaning that there are atoms of at least two different elements in the ring (the opposite of a homocyclic compound that has only one element in the ring). They can be inorganic, but the ones of interest contain at least one carbon. In the case here, the second element is nitrogen.
     The conclusions result from a computationally intensive calculation of conditions produced in shock waves produced by a comet impact on the earth. The comet is described as a CO2-rich icy body; the source of nitrogen isn't specified in the ScienceDaily article, but it implies that the nitrogen is contained within the comet and was not from our own atmosphere. Comets typically contain ammonia (NH3), carbon dioxide and monoxide, and methane, so perhaps the nitrogen is from the ammonia.
    I've posted a bit about impacts on the Moon, and meteor over Russia here. Here's a bit more on what happens. A typical comet impact velocity is about 50 kilometers a second (112,000 miles per hour!). Comets have a fairly low density (somewhere between porous ice and rocky ice), and they react ("burn") as they descend into our nitrogen-rich atmosphere.  They generate a strong shock wave in the atmosphere, creating a high-temperature, high-pressure blanket ahead of them as they soar to earth.
     Upon crashing to earth, two shock waves are generated. One spreads out into the ground telling the earth, so to speak, that the comet has arrived. The other spreads back into the comet, telling it, so to speak, that it has just run into an obstacle (the comet was already alerted that something had changed by shock waves sent into it during its descent through the atmosphere). A set of conservation equations, known as the Rankine-Hugoniot equations, govern the mass, momentum and energy conditions during the impact. When these shock waves arrive at free surfaces (the rear-end and sides of the comet, the surface of the earth), they reflect as expansion ("rarefaction") waves and these waves eventually reduce the pressures back to ambient.  However, energy is irreversibly deposited in the ground in the form of heat. To first order, the comet is entirely vaporized in the event.
     Goldman and Tamblyn used huge supercomputers at LLBL to solve not only the equations of motion, but equations for chemical reactions during the shock process, to arrive at their conclusions.  These computers calculate reactions at time steps of picoseconds.  Previously computers could only capture 10-30 picoseconds of reactions, not enough time for equilbrium, but with more efficient codes, they were able to run the computations for hundreds of picoseconds, time enough to allow approach to chemical equilibrium. Comets impacting rock at these velocities typically generate peak pressures in the megabar (Mb) range, millions of times our own atmospheric pressure. At these peak pressures, everything vaporizes.
     Of more interest are the chemical reactions in the range of 480-600 kilobars (480,000-600,000 times atmospheric pressure). At these pressures temperatures reach 6,200-8,180 F, and methane and formaldehyde are synthesized. These are known precursors of amino acids and complex organic compounds. As pressure decays in the rarefaction wave, significan quantities of simple, carbon-nitrogen bonded compunds that are known prebiotic precursors are produced.
     At lower pressures, in the range of 360 kb and 4,600 F, nitrogen-containing heterocycles, which can dissociate to form "functionalized aromatic hydrocarbons" in the rarefaction are produced. These are thought to be prebiotic precursors to DNA and RNA base pairs.
     The bottom line is that the "special conditions," such as UV radiation or the presence of catalysts, in many existing models for the origin of life on earth are not needed in this model. It's a simple physical model of chemistry during the impact process.  Some aspects of this may be amenable to experimental testing, and it will be interesting to see the full paper in a few weeks.