Underlinings (#67)

What Challenger did:

… Only a word by way of epilogue. It is of course well known that the effect of the experiment was a world-wide one. It is true that nowhere did the injured planet emit such a howl as at the actual point of penetration, but she showed that she was indeed one entity by her conduct elsewhere. Through every vent and every volcano she voiced her indignation. Hecla bellowed until the Icelanders feared a cataclysm. Vesuvius blew its head off. Etna spewed up a quantity of lava, and a suit of half-a-million lira damages has been decided against Challenger in the Italian Courts for the destruction of vineyards. Even in Mexico and in the belt of Central America there were signs of intense Plutonic indignation, and the howls of Stromboli filled the whole Eastern Mediterranean. It has been the common ambition of mankind to set the whole world talking. To set the whole world screaming was the privilege of Challenger alone.

Underlinings (#53)

On the K/T-missile and its impact:

In one of the greatest titled books ever, T. rex and the Crater of Doom, Walter Alvarez told the story of how he and his nobel prize-winning physicist father Luis revolutionised our understanding of the end of the dinosaurs. [Walter] … discovered that the boundary layer in rocks found at Gubbio in Italy contained ten times the normal levels of the metal iridium. […] … Luis had the insight that such a high concentration of the metal in one layer of rock meant it must have arrived in one huge asteroid impact. The team then confirmed another iridium spike in a Cretaceous-Paleogene boundary rock section at Stevns Klint in Denmark. […] They reasoned that the spikes implied there had been an asteroid impact so big that it threw enough dust (including tiny particles of iridium) into the atmosphere to black out the sun around the globe. This would have prevented plants from photosynthesising and, as was later suggested, caused global freezing for a short time, leading to the mass extinction of many species. They worked out that such an asteroid would have weighed at least 34 billion tonnes and measured around 7km in diameter, producing a crater around 100–200km across. […] … However, it still took a while to locate the Chicxulub crater because it had been completely covered by sediments deposited in the previous 66m years. And while half of it lies under dense tropical rainforest, the other half is beneath the Caribbean seabed. Hildebrand used evidence from boreholes made by Mexican oil company Pemex in the 1960s to prove the crater’s existence. Subsequent geophysical surveys that can scan below the surface have established the exact size and shape of the structure, which is roughly circular with three concentric rings, as you would expect from a massive impact.

Cthelll Vortex

‘Planetary gyre, time-dependent eddies, torsional waves, and equatorial jets at the Earth’s core surface’, N Gillet, D Jault, C. C. Finlay (Submitted on 29 Feb 2016), abstract:

We report a calculation of time-dependent quasi-geostrophic core flows for 1940-2010. Inverting recursively for an ensemble of solutions, we evaluate the main source of uncertainties, namely the model errors arising from interactions between unresolved core surface motions and magnetic fields. Temporal correlations of these uncertainties are accounted for. The covariance matrix for the flow coefficients is also obtained recursively from the dispersion of an ensemble of solutions. Maps of the flow at the core surface show, upon a planetary-scale gyre, time-dependent large-scale eddies at mid-latitudes and vigorous azimuthal jets in the equatorial belt. The stationary part of the flow predominates on all the spatial scales that we can resolve. We retrieve torsional waves that explain the length-of-day changes at 4 to 9.5 years periods. These waves may be triggered by the nonlinear interaction between the magnetic field and sub-decadal non-zonal motions within the fluid outer core. Both the zonal and the more energetic non-zonal interannual motions were particularly intense close to the equator (below 10 degrees latitude) between 1995 and 2010. We revise down the amplitude of the decade fluctuations of the planetary scale circulation and find that electromagnetic core-mantle coupling is not the main mechanism for angular momentum exchanges on decadal time scales if mantle conductance is 3 10 8 S or lower.