Comments by g-21-lto

Comment #277969 by g-21-lto on November 4, 2008 at 10:06 am

I voted absentee last week. That's one vote for Obama in Virginia, and a vote for the democratic senate candidate, Warner, who seems to have a nice grasp on reality when it comes to energy policy and taxes.

2. World's oldest rocks discovered in Canada

Comment #254963 by g-21-lto on September 26, 2008 at 1:52 pm

Eamonn: the particular dating method they were using is based on the decay of samarium-146, which has a relatively short half-life of 103 million years. Any samarium-146 extant at the dawn of the solar system would have been basically extinct any later than ~4.1 billion years before the present day, so any heterogeneities in the distribution of its daughter isotope, neodymium-142, must have been formed pre-4.1 Gyr. Hence the age limits on the technique.

3. The Passion of 'Anonymous'

Comment #124440 by g-21-lto on February 9, 2008 at 12:54 pm

I must say the part of this I find most interesting is Anonymous pursuing what appears to be a serious cause. Almost paradoxical. But more power to him.

4. Sea floor records ancient Earth

Comment #27463 by g-21-lto on March 24, 2007 at 6:06 pm

BicycleRepairMan -- there are several good lines of evidence for subduction occuring. One would be the existence of Wadati-Benioff Zones, which are dipping, ~planar zones of deep earthquakes (too deep to be explained by much other than unusually cold material, given the heat and relative lack of rigidity of material normally found at those depths), are best explained by the subduction of slabs of cold, rigid oceanic lithosphere. Wiki has a page on Wadati-Benioff zones if you want to check it out.

Also, the volcanic arcs associated with supposed subduction zones erupt lavas that have chemical signatures best explained by the presence of water at depth during the melting process. This water is most easily supplied by the loss of water from a subducting oceanic slab as it descends and heats up.