7 May, 2012,
Click here for a review by Don Anderson of the book "The Eruptions That Shook the World".–WM

4 May, 2012
Dear WM, Please add a link to my web page on the Ethiopian Rift Valley in my mantleplumes webpage. –Giacomo Corti

30 April, 2012
Dear WM, I would like to draw your attention to this article "A hotspot alternative" recently posted on about.com.–Phil Gibbard

31 March, 2012
Dear WM, I think it would be a good idea to post the classical paper by Roeder & Emslie (1970) which, for the first time, defined the correlation of Mg/Fe between olivines crystallizing from basaltic melts. It is a very old paper, but all Tp estimates are based on this paper. Considering that the alleged higher Tp of mantle-plume-derived melts are based on the presence of high-Mg olivines, interpreted as an evidence for high-Mg liquids, and, consequently, higher than "usual" temperatures (to extract more Mg from peridotites) it would be instructive to have such a paper posted on the site.–Michele Lustrino

29 March, 2012,
Dear WM, We have two hard constraints on the temperature of the mantle, the P and T of melt extraction at Hawaii and at ridges. These constraints require that the geotherm at ridges must graze the volatile-free lherzolite solidus at about 60 km depth. The standard complaint against this hard constraint is that we are missing this or that component. But at these low pressures, we now have data in 6-space (CaO-MgO-Al2O3-SiO2-Na20-FeO) and 98% of the composition of basalts so it is unlikely that any unmodeled component or other will change the conclusion much. At Hawaii, there is one published trend of olivine-controlled crystallization (Clague), which requires melt extraction at much higher pressures. The olivine-rich end of thIs trend intersects the experimentally-determined trend of pressure vs initial melt composition at about 5 GPa. So for this trend, the melts come from about 150 km depth, and the geotherm at Hawaii must graze the geotherm at about this depth. In my recent J. Pet. paper, for higher pressures, I assumed a 1500 C adiabat at Hawaii. For ridges, I connected the 60 km point on the geotherm at about 1.3 GPa with what I assumed was a fairly uniform temperature (a 1500 C adiabat) at great depths. Except for the temperature constraint at ~1.3 GPa. My guess that temperatures at great depth are fairly uniform could easily be wrong. But I feel very secure about the two different P-T ranges for melt-extraction at Hawaii and MORBs.–Dean Presnall