One of the key assumptions in applying metamorphic petrology to tectonics (among other fields) is the assumption that the pressure of a metamorphic reaction is the same as the weight of the rock above that reaction. This makes things reasonably straightforward in interpreting the presence of certain minerals: if you see coesite, for instance, in a rock, you should be at a pressure of 28 kbar (2.8 GPa) or higher (a depth of about 100 km if the average density above is 2850 kg/m3). Discovery of very tiny diamonds and other ultra-high pressure minerals have suggested over the past decade that pieces of continental rock make it to great depths in the earth, far below the deepest continental crust.
Lurking in the shadows for several decades has been the specter that the assumption of equivalent pressures is wrong; that is, the existence of differential stresses at a point means that you can grow minerals that “belong” at a different depth (and also that stress concentrations within a polymineralic material could also affect the minerals that are stable). (Differential stress means that the stress in different orientations is different, unlike in a fluid like water, where the pressure in all orientations is the same. Move a balloon up and down in water and you will see it expand or contract; put it in a vice and its shape will change). A new paper in Geology (accompanied by a nice overview article) brings this problem to a head by explicitly describing how, in a rock with multiple minerals, application of a differential stress can generate new minerals seemingly requiring a different pressure.
GG was in Yosemite recently and checked out some of the museums and got to thinking, how is the reinventing of museums working out?
Consider the old Happy Isles Nature Center. It was for a long time the classic old building filled with stuffed critters with tags with the common name and Latin name and so on, and some bones and fur you could touch. The materials had gotten ratty in places and it seemed somewhat dingy and old-fashioned. The park service decided some time ago that an update was in order and they transformed the space into an inviting large room with big pictures and a diorama. Many visitors are pleased with the new experience. It feels much more modern, but is it better?
It kind of seemed like you could have taken all the text on the displays and it might have filled a four page pamphlet. Hmm, yes, bears destroy cars–check. That’s a squirrel, that’s a mountain lion, ok, got it. Perfect for a five minute tour through the museum. Go through the main visitor center museum and the information feels even less dense. To be fair, some of this is because GG is very familiar with a lot of this material, but really it just seems very big for the material being presented.
Museums used to be one of the places you would go to learn about a place or event or some class of things. A lot of what museums used to offer is now available through the internet or mobile device apps. What is their role going forward? Why go in a museum?
Last fall, Boulder Colorado and environs experienced a rather dramatic event, experiencing 9 inches of rain in 24 hours (the monthly record prior to this event was only 9.6″). The usual analysis of how often we might expect such tremendous rainfall suggests an event like this should occur in a given year with a probability below one in a thousand (thus this might be termed a thousand-year rain). There are questions out there about just exactly how you derive such probabilities (unless you observe a thousand years of weather, you are extrapolating from a smaller subset of observations and to do that, you have to assume some kind of probability distribution). Basically, when you plot the probability of an event versus the magnitude of the event, you get some big lump (or lumps) where most things happen and these trail off into long, thin “tails”. So, for instance, the rainfall record from Boulder is shown below; you can’t even see much beyond 1″.
(If you are wondering, Boulder has had 344 days with 1″ or more of precipitation out of the 38404 days where records were kept, or just under 1% of the time. 2″ or more has occurred only 49 times, 3″ or more 12 times. Note that these include snowfalls–three of the 12 3″+ events were associated with heavy snowfall as were 9 of the 49 2″+ events).
Set aside for the moment the statistical issues and consider the geological impact of the weather on those 38,404 days. Read More…
In reading a post on how the children’s classic, “Goodnight Moon” follows some unexpected tangents, making it a richer and more literary tale, GG was reminded of choices made in making lectures over the years.
Is a better lecture one that is crystal clear, well signposted and free of distractions? Or one that meanders, allows for sidetracks and elements that perhaps aren’t anticipated or even strictly relevant? Students often plead for the former, but is that really the best?
Consider people who tell stories (as opposed to those who write them). We don’t have many left; one of the more prominent is Garrison Keillor. One of his monologues will often start in one direction, suddenly veer off in another, often introducing new characters, perhaps slam on the brakes and return to the first plot line before discovering a third, seemingly irrelevant happening. Many times these multiple lines collide at the end, revealing connections and insights that were unanticipated. So why does he do that? Wouldn’t a more straightforward telling be better?
Came across an article about how the threat of coastal land being declared undevelopable seems to drive a number of people towards “climate change denial.” This is a bit of a misreading of the response, I think (it seems this is partially a response based on fear of an asset suddenly becoming worthless, partially a response of hoping for the better end of an uncertain future, and partially a distrust of government intervention as much as any disagreement over science). Anyways, the response has caused the state to mandate that they cannot plan long term for any sea level rise, which is unfortunate in a state where serious economic harm might come about from such an event.
This is not the first time that an attempt at a science-based warning upset a real estate market, which came back to curtail the scientific warning. In the early 1980s, the USGS was prepared to issue a volcano advisory for Mammoth Lakes, California. This was leaked to the L.A. Times and among other effects led to a change in the procedures for issuing such advisories. Real estate prices suffered for awhile before rebounding some years later. (The good news–aside from there being no eruption–was that the town of Mammoth Lakes was forced to make an all-season evacuation route, termed, with the best Chamber of Commerce whitewash, the Mammoth Scenic Loop). The lesson was that you simply don’t just toss out a warning that a bunch of land might be unlivable without anticipating how to mitigate the harm.
So what could be done here? People today in coastal areas are heavily invested in their land, which is presently quite valuable. That asset is expect to decline in value to zero sometime in the future. You know what, we already have a means of dealing with an asset that will decrease in value over time: it is called depreciation. If your business uses a car, you can deduct part of the car’s price over a fixed amount of time. It isn’t as though we are certain the car will fail at the end of that time; it is an estimate with considerable uncertainty, just as the inundation of parts of the coast carries uncertainty. Why not have a coastal depreciation allowance? Each year over, say, the next 100 years the owner of the land gets to claim some credit equal to 1/100th the present value of the land. So if in 50 years the owner sells the land but of course cannot get a 2010 price, they have already been compensated for that loss. This allows for more sensible planning, rights an economic wrong (those coastal residents did no more than those of us well above sea level in causing sea level to rise), and removes an incentive to put on blinders to the future. Real legislation would probably look a bit different (you might, for instance, revisit the values and times allowed every 5 or 10 years to see if the outlook used before made sense, and you might make the depreciation accelerate towards the time of expected inundation as, for instance, a beach property expected to stay above sea level for 70 years might command the same price as one that will be around 100 years), but you get the idea.
Of course that money comes out of everybody else’s pocket; is that fair? GG isn’t fond of making coastal landowners whole when their beach abode gets obliterated by hurricanes in places like barrier islands where we know (and have known for a long time) that such obliteration was only a matter of time. But in this case, where recognition that sea level rise from human activity is a new risk, one we all have shared in creating, it makes sense for all of us to share in the cost.
One thing this would do is make extremely apparent the cost of not addressing climate change (and mind, there are other potential losers out there who might also want some aid, from farmers who may face heat-stressed crops to vacation destinations that will no longer be attractive). And as there is evidence that we will see sea level rise from the destabilized parts of the Antarctic ice sheet regardless of our ability to rein in global warming, this might be an effect we cannot hope to avoid but can only adapt to.
Its been a busy week or so for earthquakes and the oil and gas industry. In Colorado, a wastewater well was shut down after the Colorado Oil and Gas Commission requested that they do so while the cause of a series of small earthquakes is investigated. In Kansas, in contrast, a strong increase in seismicity in an area with extensive oil and gas activity remains controversial as progress on a commission set up by the governor last February remains slow. And in Oklahoma, things are hopping as residents of Edmond, Oklahoma, met to consider banning industry activity producing earthquakes in the area. [We’ll leave Texas to the side for now; it is a separate challenge].
There are some priceless comments justifying the continued use of the injection wells coming from the Oklahoma meeting. GG’s fav:
[Oklahoma Geological Survey seismologist Austin] Holland said stopping the use of injection wells, which pump water deep underground, would not be recommended from a scientific standpoint because that would rob researchers of valuation data that could help them figure out how to prevent earthquakes.
One can only hope he said “valuable data”. Anyways, this is silly as stopping injection would also produce valuable data (arguably, seeing the seismicity die off or continue would be pretty diagnostic–this was pretty clear in the case of the seismicity from the Rocky Mountain Arsenal in the 1960s). Pretending that continued injection is a valuable scientific experiment instead of an expensive commercial activity is ridiculous and casts real doubt on the professionalism of the Oklahoma Geological Survey. One can hope the media quote was sufficiently out of context that this wasn’t as silly as it sounds.
How do we make technical decisions as a society? Very poorly, which saddens the Grumpy Geophysicist. Join GG in the way-back machine to revisit one of those strange moments when geology and public policy came together to make a lot of people spend a lot of time producing nothing (when, in fact, a lot of something was needed). As we shall see, there are oodles of blame and silliness to go around.
It has been noted for a long time that we need a secure place for nuclear waste. It is kind of dangerous stuff, and you don’t want to be finding it in your dumpster or in the air or, well, anywhere you want to be. So long ago Congress decided to tax nuclear power in order to pay to find a place to put the waste.
Fine so far, good idea. But what to do? Well, of course, we call it waste and so we should dump it, no? This means putting it somewhere out of sight and out of mind. Let’s pause for a moment to consider that this waste represents a bunch of heavy elements that are really really rare and occasionally have other uses than making power or blowing things up and so just sweeping this under the rug may not be the best long term solution.
Enjoyed the pause? Ok, back to reality. Being waste, you need to put it somewhere really safe, preferably bury it somewhere. Being Congress, they heard this stuff could be hazardous for a long time, so they mandated that material could not somehow escape for 10,000 years (technically they mandated that the National Academy of Science determine if this was possible).