EGU Blogs

Geology Photo of the Week #30

April 17, 2013 Photo of the Week 5 Comments

The photo for this week was taken in Quebec near the town of Thetford. These are a really beautiful example of pillow basalts. Pillow basalts form during underwater volcanic eruptions and have the unusual quality of appearing bulbous and rounded. The ones pictured below have had their tops shorn off and are therefore visible in plane view. e.g. You’re looking down at them from above after they have had the tops cut off. As I mentioned above these particular pillows are located in Thetford Mines, which is a mining town (obviously). The principle commodity of Thetford Mines is the extremely dangerous and controversial mineral asbestos.

Here is a fantastic video showing pillow basalts forming today.

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Cheers,

Matt

 

By
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.


5 Comments

  1. Your photo also does an awesome job of illustrating how pillows can give sense of stratigraphic “up.” The bottoms of younger/higher pillows conform to the tops of older/lower pillows. So in this case, stratigraphic up is toward the top of the photo.

    • Great point Lockwood! I forgot to mention that. Thanks for the comment.

  2. I live in Thetford mines and I have seen these pillows and they are really great. Its not shown in this picture but in some cases there are quartz cores in them. It’s a great representation of miniature magma chambers. These can be found a little bit everywhere around the city (pillow basalts). Great pic!!!

    • Thanks for the comment! I’d love to see some more pictures of Thetford Mines geology, especially the ones with the quartz cores. That is pretty cool. Obviously the mine is also pretty impressive.

      • No problem. I have a few already on hand and soon I was thinking of getting going around to take some new pics. Where can i send them to you ?

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