Recently the libraries of the University of California system finally pulled the plug on the predatory pricing policies of Elsevier. All GG can say is, finally! [Note: GG has not reviewed or published with Elsevier as a matter of principle, only making the mistake of agreeing once to a review by accident]. What does this mean?
According to Marcus Banks, writing at Undark.org, it means that pure open access is the way out of this. His text implies that the costs of publication are so low that it is ridiculous to have such expenses, and he implies that prestige publications are really a sham for fleecing the scientific public. The sooner that academics realize that the open access journals are just as good, the sooner all will be right in the publishing world.
OK, now maybe GG has read a bit more into this essay than is really there, but there is this sense that all publishers really do is collect money off the backs of funding agencies for no good reason. And this logic can lead to a terrible decay in journal quality.
Long ago the United States decided that public education was good. Students gained skills. Employers had bigger, better labor pools to draw on. And the country had voters engaged in helping to run the country, from voting in national elections to populating everything from school boards to Congress. And recognizing that educating those students was helping everybody, the nation agreed to have everybody help pay for education–in essence, recognizing that public education was a public good.
The current debate over proposals to make college free essentially boils down to this: is higher education a private good–benefiting only the student–or a public good?
We’ve discussed isostasy a few times here, but today let’s stand back and ask the question, how do we determine what has led to the creation of isostatically supported topography? We will for today put aside the discussions of dynamic topography and just concern ourselves with isostatically supported topography, which seems likely to describe much of the US Cordillera. For this post, we’ll just focus on the crustal part of the problem, leaving the mantle for another day.
OK, first up is that isostasy means that the integral of density from the surface to some depth of compensation (usually somewhere in the asthenosphere) is constant. So how do we get at density at such great depths? At first blush you might think “gravity” as that is the geophysical observable produced by mass. The problem is that gravity is non-unique: you can recreate any gravity field by having a thin surface layer varying in density. Gravity gradients tell you of the maximum depth an anomaly can lie, and the integral over a broad region tells you of the total mass surplus or deficit relative to some reference. Those integrals support isostasy, but the gradients are tough to work with because isostasy is only thought to work well at long enough wavelengths that the strength of the lithosphere becomes irrelevant. So in essence you need to smooth gravity out to appropriate wavelengths–and once you do that, the depth limits in the raw gravity are pretty much gone.
So with gravity being relatively useless, where do we go? Keep in mind that we’ll be wanting to compare two columns to be able to discern what happened at one column relative to the other to produce a difference in elevation.
Consider for a moment the geoid, which is the difference in elevation between a reference spheroid and an equipotential. The geoid has lots of neat properties, among them being directly related to the gravitational potential energy in the lithosphere. It is sensitive to density variations at great depths and so can give us insight into deep earth processes. But there are some issues that casual readers of papers using geoid might want to be aware of.
Geoid has long been recognized as having a sensitivity to greater depths than gravity, but this is a mixed blessing as density variations far below the asthenosphere can affect the geoid, complicating a lithospheric interpretation. The most common approach is to filter the geoid to eliminate long wavelengths that are most sensitive to deep structure–but these same wavelengths are also sensitive to the difference between continents and oceans. In the western U.S., the look you get from the geoid depends on how you filter it. For instance, these are two images of the geoid, one as published in Jones et al., Nature, 1996, and the other with a different filter.
The clearest difference is at the right, where the solid zero line has moved a lot, but also note that the scale of the color bar has changed. It can be a bit hard to compare these, so another way of looking at it is to plot some points from each against each other:
The diagonal line would be where points would plot if both filters yielded the same values. Clearly the southern Rockies (SRM) pick up a lot of power in the degree and order 7-10 range compared with, say, the Sierra Nevada (SN). If interpreting this for potential energy, at D&O >7 taper to 11 the western Great Plains (GP) would have a positive GPE and would be expected to have normal faulting, but at D&O >10 taper to 15 it would be quite negative and you would expect to have compressional stresses and possible reverse faulting.
(Beyond the issues with the edge of the filter is the nature of the taper–a brute force cutoff can produce some artifacts you might not want to interpret.)
Anyways, what is the appropriate filter? There is no simple answer for three reasons. One is that the maximum depth you might care about probably varies across the region so a filter that cuts off in the asthenosphere in one place might also cut off the lower lithosphere in another. Another is that there is significant shallow power in the longer wavelengths/lower orders: continent/ocean boundaries have some real power in low degrees and orders. So when you filter out the long wavelengths, you can be removing shallow signal as well as deep signal. The third is that the sensitivity with depth is gradational, so a filter won’t fully cut off greater depths unless there is reduction in power from shallower ones.
(If you are wondering, in the paper we chose D&O 7-11 as the most appropriate filter for our purposes).
So be cautious when a filtered geoid is presented as a purely lithospheric signal, for it could be contaminated with deep sources or cutting off shallow ones.
Recently NSF’s EarthScope program office put out a media announcement with the top ten discoveries they attributed to the soon-to-end program. (EarthScope, for those unfamiliar with the program, originally had three main legs: the Transportable Array (TA) + Flex Array collection of seismometers, the Plate Boundary Observatory (PBO) network of GPS stations, and the San Andreas Fault Observatory at Depth (SAFOD), a drill hole through the fault). What struck GG about this collection was just how little we learned about tectonics, which was a selling point of sorts for the program prior to its start.
Now some of the “discoveries” are not discoveries at all–one listed is that there is a lot of open data. Folks, that was a *design*, not a discovery. A couple are so vague as to be pointless–North America is “under pressure” and there are “ups and downs” in drought–stuff we knew well before EarthScope, so these bullets give little insight to what refinements arose from EarthScope. And then the use of LIDAR to look at displacements of the El Mayor-Cucapah earthquake was hardly a core EarthScope tool or goal even as the program might have contributed funds. So the more substantive stuff might amount to 5 or 6 points.
Arguably PBO has more than delivered and SAFOD disappointed, but GG would like to consider the TA’s accomplishments–or non-accomplishments. TA-related “discoveries” in this list are actually a single imaging result and two technique developments (ambient noise tomography, which emerged largely by happy coincidence, and source back projection for earthquake slip, which is largely a continued growth of preexisting techniques). So in terms of learning about the earth, we are really looking at one result worthy of inclusion.
The New York Times has swung its spotlight on Boulder once again, but this time with the somewhat implausible notion that CU is leading the way to end college football. The motivation for the piece is a pair of votes by two regents against approving the contract for a new football coach–not because of any objection to the coach himself, but to protest supporting a game that damages the brains of its players.
This arguably is the third strike against football here at CU, but don’t expect any changes. There was first a series of recruiting scandals that took out most of the university administration, then there continues to be an uproar over the amount of money collected and spent on football and how little goes to benefit players, and now we are recognizing the incongruity of higher education being the site for systematic brain damage leading to early death or suicide. Add them all up you’d think this would be the death knell for the sport at CU. Don’t hold your breath, (though it would probably end college admissions scams we’ve heard so much about recently)….
…is death on a class trip. Going to places with unstable footing and exposure is often part of seeing geology that clarifies understanding, but it carries real risks. For GG, the most terrifying site is Toroweap Point in Grand Canyon National Park where, every time he visits, he breathes a sign of relief when the same number of students pile back into vehicles that had piled out of them. That site has 3000′ of vertical cliff to punish the unwary, but it doesn’t take that much for a fatality, as an environmental studies class from Briar Cliff University found out when they lost a classmate to a 100′ fall.
While family and friends grieve, another discussion is probably going on, if not now then soon. Should the school curtail field expeditions? Given the growing number of deaths by selfie, what is the role (and responsibility) of the instructor who takes students to places with hazards? Should the school dictate what is and is not an acceptable risk? Should students sign waivers, and if so, are they really enforceable?
Geoscience education benefits immensely from seeing what you are studying in the field. And the greatest hazard in field trips is generally the drive to the field or working on roadcuts near highways. But the drama of a fatal fall is more damning in some ways. GG hopes that future students will get to experience the field safely, hopefully mainly by recognizing and avoiding hazardous situations on their own and with the guidance of an instructor rather than by being blocked from accessing important or memorable sites by fearful administrators.