Columns in an ignimbrite on the east side of Santa Maria volcano in Guatemala. (A drive-by, unfortunately. I would have loved a close-up look at these!)
Some of the oldest volcanics in the Vulsini volcanic district, Italy: a jointed trachyte from the Bolsena caldera complex. (The tree at the top of the cliff is about 3 m tall.) This is one of my favorite photos, because you can see multiple cooling sets divided by fractures - and it really emphasizes how columns form from inward-directed cooling.
And, finally, an actual example of columnar jointing in basalt, which is probably much more common than jointing in an any of the other stuff I've mentioned: a lava flow near St. George, Utah. (Wish I could figure out where, but Google Earth isn't helping today. Has anyone seen this abandoned water tank?)
Perhaps we should submit a request for a Columnar Jointing Week to someone in Washington. As far as I can tell, we're sadly lacking in geological observances anyway...
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I really like the picture of the jointed trachyte. Is that the name for such a radial cooling pattern (if that makes sense)? There's an outcrop in the Columbia River Gorge that exhibits the same pattern. I never knew what it was called though.
(Wish I could figure out where, but Google Earth isn't helping today. Has anyone seen this abandoned water tank?)
This picture is of a scene just north of St. George -- people drive right by it on I-15 all the time (between exits 13 and 16 from I-15), but only we select few know how cool it really is....
From Dave Tucker at Northwest Geology Field Trips:
Dear Tuff Cookie and friends of columnar jointing,
I took Jessica’s comment about someone in Washington declaraing ‘Columnar Jointing Week’ literally and decided it would be quicker and easier to post pics of columns in Washington State rather than wait ‘for someone in Washington’ to declare National Columnar Jointing Week.
The post and pictures can be found at http://nwgeology.wordpress.com/2010/09/29/columnar-jointing-in-washington/
Got you the coordinates of the St. George basalt on Google Earth: 37°09'29.64"N, 113°28'22.11"W.
Hi Jessica! My Volcanology Group runs a Volcano blog (deliberately in Hungarian language). Following your announcement to have a Columnar Jointing week I posted selected photos from the exceptional nice columnar jointed volcanic rocks of the Carpathian-Pannonian region, eastern-central Europe. Visit: http://tuzhanyo.blogspot.com/2010/10/oszlopos-lavakozetek-kiveteles.html
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