The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. Now, 2015, the blog/podcast is on a 3 or 4 per month schedule with diverse topics.

Wednesday, February 25, 2015

The Ordovician Episodes





Running time 2 hours 15 minutes

This episode is the third monthly package of the History of the Earth calendar. It combines the daily episodes for March 2014, covering the Ordovician Period of the Paleozoic Era.

You’ll find that I’ve left the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.

As the year continues, there will be occasional new episodes in addition to these monthly assemblies.
If you have questions or comments, please let me know, either here on the blog – there’s a page for asking questions tabbed above – or contact me by email at rigibson at earthlink.net. I’ll try to respond. You can of course also leave a review on iTunes. I really do appreciate your feedback.


—Richard I. Gibson

Saturday, February 14, 2015

Episode 369: Gallium



On my What Things Are Made of blog, by far the most popular post is one on the element gallium. I don’t know why this is so, unless there are a lot of middle schools assigning homework on gallium. So I thought I’d update that post here for the podcast.

Gallium is an element isolated in 1875 by French chemist Paul Lecoq de Boisbaudran, who named it for his native France or Gaul, Gallia in Latin. It proved the predictive validity of Mendeleyev’s then new Periodic Table of the Elements, in which Mendeleyev had predicted the element in 1870. Gallium is extremely rare in terms of gallium minerals. There’s one, gallite, a copper gallium sulfide, but most gallium occurs as traces in other minerals, and most of it is recovered during processing of aluminum and zinc ores, bauxite and sphalerite, where it can occur at up to 50 parts per million. Not much, but enough to be economically recoverable.

So what? Well, virtually every American uses gallium virtually every day. Not much, but it’s critical in things like semi-conductors and integrated circuits in computers and televisions, cell phones, LEDs in street lights, solar panels, and more. About three-quarters of the gallium used in the United States goes to integrated circuits in the forms of gallium arsenide and gallium nitride. Most of the rest is in devices such as lasers, LEDs, telecommunications, and solar cells. Gallium has also been used as an additive to ski wax, where it helps reduce friction on the surface.

The United States hasn’t produced gallium since 1987, so it’s entirely dependent on imports. As with many mineral products, China is the world leader in gallium production with about 80% of the total, and they’ve really ramped up their production in recent years, leading to a decline in the price of gallium from almost $700 per kilogram in 2011 to $240 per kilogram in September 2014. Even though supply increased by 26% in 2014 over 2013, so did demand, especially as Asia increases its electronics usage. An increasing use for gallium is in thin-film solar cells, made with copper-indium-gallium diselenide, an alloy with photoelectric properties.

About a third of U.S. imports come from metal refineries in Germany, with another quarter from the U.K. and the same amount from China. Ukraine provides about 6% of U.S. gallium. Total U.S. consumption is about 40,000 kilograms a year, or about 88,000 pounds. Not much compared to, say, almost a million tons of zinc the U.S. consumes annually – but as I suggested earlier, gallium is pretty critical to the modern American lifestyle.

—Richard I. Gibson

Resource: USGS Mineral Commodities Summary – Gallium

Sunday, February 1, 2015

The Cambrian Episodes





Running time 2 hours 10 minutes

For 2014, the podcast consisted of daily productions averaging about 5 minutes each. The individual episodes for each month are now being assembled into packages for each month, representing various spans of time in the history of the earth. 

This episode is the second package, which combines the daily episodes for February, covering the Cambrian Period of the Paleozoic Era. This includes all the individual daily episodes from February 2014.

There is variable audio quality in some of the individual recordings, which are conversations between me and other geologists – the nerds in a bar episodes. And I’m leaving the references to specific dates in the podcast so that you can, if you want, go to the specific blog post that has links and illustrations for that episode. They are all indexed on the right-hand side of the blog.


As the year continues, there will be new episodes, maybe every week or two, in addition to these monthly assemblies.

If you have questions or comments, please let me know, either here on the blog on the ask a question page, or contact me by email at rigibson at earthlink.net. I’ll try to respond.

—Richard I. Gibson