As papers come through my RSS reader, I flag anything that looks interesting, with the vague intention of getting back to it later.
Ha, ha. Very few of the articles I flag actually make it through my periodic purging of the to-read list. Since Berkeley has finally figured out that I'm no longer a student and they should stop providing me with library access to journals, the barrier between "hm, looks interesting" and "I'm actually going to read this" has gotten even higher.
Below the fold: 5 papers that haven't quite made the hurdle.
- Dating kimberlites in Kansas - Kimberlite pipes are famous for hosting diamonds. They're interesting to non-gem-people, too, because they come from unusually deep in the mantle and are erupted very violently; I didn't know there were any in Kansas. But based on the abstract, this paper sounds like a story about fancy new radiometric dating methods, with only a very minor subplot about the kimberlites themselves. T BLACKBURN, D STOCKLI, R CARLSON, P BERENDSEN (2008). (U-Th)/He dating of kimberlites--A case study from north-eastern Kansas Earth and Planetary Science Letters DOI: 10.1016/j.epsl.2008.08.006
- Microbial communities in aquifers - Even in aquifers with fairly uniform conditions, the microbial inhabitants will be very different from place to place. Apparently the microbes set this up this by fighting with each other for some kind of biochemical control of their environment. Craig M. Bethke, Dong Ding, Qusheng Jin, Robert A. Sanford (2008). Origin of microbiological zoning in groundwater flows Geology, 36 (9) DOI: 10.1130/G24859A.1
- Frictional strength of the Chelungpu Fault - This is the fault responsible for the 1999 M7.3 earthquake in Taiwan, and the site of one of a couple major drilling projects (another is on the San Andreas, near Parkfield, California) designed to give us an up-close look at what real active faults look like and do. The clay gouge that lines this fault has a coefficient of friction of 0.3, which is twice as slippery as vulcanized rubber on cement, but half as slippery as wet waxed hickory wood and 1/3 as slippery as ebonite on ice. (I'm getting these numbers from my 1959-1960 edition of the CRC handbook; 50s engineers had interesting priorities...) K MIZOGUCHI, M TAKAHASHI, W TANIKAWA, K MASUDA, S SONG, W SOH (2008). Frictional strength of fault gouge in Taiwan Chelungpu fault obtained from TCDP Hole B Tectonophysics DOI: 10.1016/j.tecto.2008.08.009
- Smearing clay on faults - Oddly, the authors of this paper modeling the development of fault gouge found their motivation in hydrogeology, rather than earthquake physics. It's true that this clay lining can prevent water from flowing through a fault zone, which means that it's important to understand how the gouge develops... but the role of heterogeneity in determining the course of an earthquake is a popular topic in seismology, why didn't they capitalize on that? D.L. Egholm, O.R. Clausen, M. Sandiford, M.B. Kristensen, J.A. KorstgÃ¥rd (2008). The mechanics of clay smearing along faults Geology, 36 (10) DOI: 10.1130/G24975A.1
- How clay minerals control landslides - According to the abstract, potassium-rich clays are more prone to debris flows than sodium-rich clays. So the chemical whimsy of a magma chamber hundreds of millions years ago could determine whether or not your house falls down tomorrow. Robert H. Webb, Peter G. Griffiths, Lawrence P. Rudd (2008). Holocene debris flows on the Colorado Plateau: The influence of clay mineralogy and chemistry Geological Society of America Bulletin, 120 (7) DOI: 10.1130/B26055.1
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Are kimberlite eruptions really best described as erupting "very violently." On one hand, they're certainly explosive, and definitely more violent than a basalt flood or a lava fountain, such as you might see in Hawaii or Iceland. On the other hand, the average reader will conjure up images of Pinatubo, Krakatau, and Pliny when hearing a volcano described as "very violent." But don't kimberlite eruptions leave behind mostly just a moderate-sized tuff ring and a relatively unimpressive dent in the ground?
So, if we restrict the discussion to volcanoes that go "bang" instead of "gush," aren't kimberlite eruptions mostly towards the lamer end of the bang range?
I understand, though, that while kimberlite eruptions aren't particularly big, they are in one sense rather quick. Kimberlite diamonds are of course formed very deep where the pressure is high enough, but they would erode away to nothing if they were slowly transported to the surface. The fact that the diamonds survive means the magma speed must be fairly zippy, by magma-speed standards.
Some folks model kimberlites as erupting supersonically, so they'll kill you before you hear the bang.
However, the eruptive volume is very small, compared to caldera-forming arc volcanoes.
As for the last item, isn't the alkali content of the clay determined by the weathering regime, not the igneous precursor?
Kansas? Why Kansas? (I admint I know only enough about geology and plate tectonics to hurt myself...) I thought most of the kimberlites came from passing over hotspots like the Bermuda hotspot.