EGU Blogs

Matt Herod

Matt Herod is a Ph.D Candidate in the Department of Earth Sciences at the University of Ottawa in Ontario, Canada. His research focuses on the geochemistry of iodine and the radioactive isotope iodine-129. His work involves characterizing the cycle and sources of 129I in the Canadian Arctic and applying this to long term radioactive waste disposal and the effect of Fukushima fallout. His project includes field work and lab work at the André E. Lalonde 3MV AMS Laboratory. Matt blogs about any topic in geology that interests him, and attempts to make these topics understandable to everyone. Tweets as @GeoHerod.

My DEFENCE! Follow live tweets with #129I @ 2:30pm ET

My PhD defence is this week (Wednesday) at 2:30pm ET. I am feeling pretty good about the whole thing but at the same time nervous. I just don’t know exactly what to expect. I have a sort of idea of what the questions might cover and where my assumptions or conclusions might be challenged. However, the uncertainty of all this is what is making me nervous.

Credit: XKCD

I have gotten lots of good advice from people such as “you are the real expert on the material” and “be confident and prepare a great talk”. All of this is great advice, however it doesn’t really help assuage the feeling that this is the most important talk I have ever given and the nerves that accompany that. Furthermore, despite the fact that I am now an expert on 129I I still have to convince four very smart people that I what I did was worthwhile and good science.

As far as my preparations go I have read lots of articles from fellow bloggers about how to prepare and what to think about and talked to postdocs in the lab. These have all been very helpful things to do, but at the end of the day I know that I will be the one standing at the front of the room and facing the steely gaze of the examiners (not really, they are all nice people). I have read over my thesis several times, prepared a list of possible questions, re-read key articles and reviewed the basic principles of the models I used and the statistical tests. I still feel unprepared and I doubt that feeling will go away until I start my talk. Plus, thesis committees are still scary!

Credit: PhD Comics

Anyway, in the interest of distracting myself yet also being sort of productive I am preparing to live-tweet my defence. I am pre-scheduling about 20-30 tweets for the time during my talk so you can view these key points of my thesis as I talk about them at uOttawa. Follow the feed with #129I. Interact with the tweets, ask questions, etc. I won’t get to them until later in the day…or maybe the next day, but I will eventually.

Wish me luck and remember, follow #129I!!!! Tweets start at 2:30pm ET.

Also, I’m using a new presentation program called SlideDog. I mean why not try something new for the most important talk of my life. Stay tuned for this:

Credit: PhD Comics

Photo of the Week #50

This week’s photo is brought to you from outer space! Indeed, this a beautiful cut section of a meteorite that fell in northwest Australia and was found in 1892 (ignore the label behind it). It is an iron-nickel meteorite and is composed entirely of metal. This crazy cross-hatching, which is most commonly found in such iron-nickel meteorites, is called a Widmanstätten pattern.

Widmanstätten patterns, also known as Thomson patterns, are revealed only when the meteorite is cut, polished and acid etched. The patterns formed when the meteorite cooled and only do so if the meteorite cooled very slowly i.e. over millions of years.

First, when the meteorite is hot the entire thing is mono-crystalline and is formed of an Fe-Ni phase called taenite. However, as a it cools another phase develops called kamacite (low Ni) which grows within the existing taneite (high Ni) lattice resulting in the Widmanstätten pattern.

Iron meteorite found in Roeburne, Hammersley Range, NW Australia. This piece is exhibited in the Museum Reich der Kristalle, Munich, Konstantinos Kourtidis

Iron meteorite found in Roeburne, Hammersley Range, NW Australia. This piece is exhibited in the Museum Reich der Kristalle, Munich, Germany by Konstantinos Kourtidis

From the GeoSphere Archives: The Wooden Wall

It is once again time to write about geology and classics and the incredibly important impact the geosciences had on the ancients and their way of life. My previous post on this topic can be found at my old blog location as the post: The Odyssey and Geology. I’ll begin by relating a story:


Themistocles (Wikimedia Commons)

The two fleets, the Persians the the Greeks, which was composed of the navies of all the city states, but mainly Athens, met in the narrow Strait of Salamis for a final and deciding battle. The Persian king, Xerxes, was so certain of victory that he set up a throne in nearby Athens to watch the battle. The true architect of the battle though was not Xerxes, but the Athenian Themistocles, a politician and general. Indeed, it had been Themistocles who had convinced the Athenians to build a navy of over 200 additional ships in the years prior to the war and it was he who stationed the Greek navy in the Strait of Salamis, which was advantageous for the smaller Greek navy. The battle proceeded according to Themistocles’ plan and the Greeks were able to out-maneuver the Persians in the narrow strait and succeeded in decimating the Persian navy. This was a great blow to Xerxes who fled back to Persia with much of his army. The next year the Greeks were able to defeat the remainder of the Persian army driving them out of Greece and winning the war. Salamis was the turning point of the war and saved Greece from certain doom.In 480 BC the ancient Greeks were faced with their biggest threat in history: the invasion of the Persian king, Xerxes and his armies. The Greeks, despite being horribly outnumbered had fought bravely but been defeated in the Battle of Thermopylae. The Persians then advanced through Greece nearly unchecked and conquered Athens.  However, the Persians knew that to fully conquer Greece they would have to do so at sea as well as on land. Things were looking pretty grim for the future of ancient Greece at this point.

File:Battle of salamis.png
Source: Wikimedia Commons

The hero of Salamis, Themistocles was a very persuasive politician as well as tactician. In fact, it was he who convinced the Athenians to build the 200 triremes (ships) that made of up the bulk of the Greek navy and can be credited with saving Greece. The credit cannot be only given to Themistocles though. In fact, the idea came from the Oracle of Delphi. The Greeks were very worried about the impending Persian invasion and decided to consult the oracle for advice on how to win the war. The oracle cryptically answered along the lines of the “wooden wall will save you”. Clearly, this answer could not refer to the building of an actual wooden wall since that would be stupid and obviously could burn down. Themistocles interpreted the oracles advice to mean build a navy. Unfortunately, the ancient Greeks had the same problem with national defence requisitions as governments do today and money for such a venture was not easily at hand. However, geology was going to come to the Greeks rescue in the form of a major silver discovery at Laurium, a small mining community just south of Athens, providing the Athenians with enough money to afford a new navy. Without the discovery at Laurium it is possible the navy would never have been built and ancient Greece would have fallen into Xerxes hands. Ergo, geology saved ancient Greece from total domination by the Persian empire.

So now what about Laurium?

File:Mineurs grecs 2.jpg
Miners in Laurium. They were all slaves. (Source: Wikimedia Commons)
Google Maps

The Laurium silver mines are located just south of Athens and are world renowned for the excellent mineral samples the area still produces in addition to its storied past. The mineralization is of lead, zinc and silver and is associated with the emplacement of an igneous body within metamorphosed sediments. The ore occurs mainly within marble especially at the contact with other metamorphic or igneous rocks ( The list of minerals found in the Laurium mining district is a mile long and it is actually the type locality for about a dozen minerals as well, making it a world class mineralogical site. The mineral Laurionite is named in honour of the location. In addition to the minerals occurring in the mines there are a host of others that occur in the ancient slag piles left by the Greeks. The slag has reacted with the sea water used in processing the ore in ancient times to produce a suite of new and unusual minerals there as well.

Agardite, Laurium, Greece (Source: – Used with permission)
Diaboleite, Laurium, Greece (Source: – Used with permission)
Conichalite, Laurium, Greece (Source: – Used with permission)
Nealite, Laurium, Greece (Source: – Used with permission)
Annabergite. Larrium, Greece. (Source: – Used with permission)

The ancient ore processing techniques of the Greeks were obviously primitive relative to today’s, however, they were still able to extract both lead and silver from the ore. The process essentially involved numerous washes with water in a sloped basin. The heaviest material was collected and smelted, and the resulting slag was carted away and dumped. Since then the slag has had a few thousand years to oxidize and this process has resulted in the growth of all sorts of interesting minerals like the ones pictured above. Laurium is still geologically relevant today from the perspective of the mineralogist or mineral collector as the area still produces some world class specimens.

It has always amazed me how deeply geology is integrated with our lives today, what with our dependence on natural resources for nearly everything. However, it would appear that this is not a new phenomenon and that geology always has been and will always be a crucial part of our lives.

Thanks for reading!


Photo of the Week #49

This week’s photo is from my personal research and shows a precipitate that I generated in the lab one day of AgI (silver iodide) for analysis of 129I by accelerator mass spectrometry.

I felt though that I wanted to verify the purity of the AgI so I quickly threw in on our scanning electron microscope to a) check the chemistry and b) take a picture. The image below shows an amalgam of AgI crystals with a scale of 20 microns at 600 times magnification.


By the way, to any fellow Canadians reading this post. Please go vote today and be a part of our democracy!!