Sunday, April 18, 2010

Volcanoes -- modern and ancient

The recent eruption of the Eyjafjallajökull Volcano in Iceland made a lot of press lately and captured the interest of scientists and non-technical folks alike.  In this post I want to compare and contrast the modern volcanism in Iceland with the Neogene-Quaternary volcanic setting in Romania and, in doing so, to briefly review two different tectonic settings in which volcanic activity may take place.

Iceland is located at a divergent plate boundary over the Mid-Atlantic Ridge, along which the North American Plate and Eurasian Plate are being pushed apart by newly formed crust (diagram below from USGS Credit: U.S. Geological Survey Department of the Interior/USGS)

A deep-seated mantle plume is also present in the area and interacts with the North American Plate.  This plume (or hotspot) and the active spreading axes are producing the volcanism of present day Iceland. The map below (from R.G. Trønnes, Nordic volcanological Institute, University of Iceland) shows both the active and old spreading axes as well as the position of the mantle plume between present day and 40 million years ago.

The ash cloud from the icelandic volcanic eruption was observed in the Northern part of Romania on April 16 and 17, but Romania had ash produced from its own volcanoes as recently as 10,000 years ago.  In contrast to Iceland, the Romanian volcanoes were active at a convergent plate margin.  The resulting volcanic arc deposits are Neogene to Quaternary in age and are located in the Northern part of the Eastern Carpathian mountains.  The map below (from A. Szakracs,I. Seghedi, 1995) shows the volcanic cones and the associated deposits in Calimani-Gurghiu-Hargita mountains.

The Eastern Carpathians volcanic arc is 160km long, the longest in the entire Carpathian mountain belt.  It formed as a result of the convergence between two plate fragments, the Transylvanian micro-plate and the Eurasian plate.  The volcanic activity spanned from ~15 Ma to 0.01 Ma ago.  The area is interesting not only from the geological point of view, but also for its natural beauty, but about this in another post.

Wednesday, April 14, 2010

Free books and ... geology of course

I was driving back home from the office today listening to NPR, and Andrei Codrescu's commentary "Getting From Here to There"  inspired me in many ways.  His story also pointed me to an iPhone app "FreeBooks", which I immediately searched for and downloaded when I arrived home.  The app is advertised as "23,469 classics for less than a cup of coffee" and I can tell that it will become one of my favorite apps.  It will take me a while to read all of this good stuff, but for sure among the first will be the "geology-flavored" books.  Here are some of them, now accessible anytime from my trusty iPhone (if I would only have more than 24h in a day):

  • The Student's Elements of Geology - by Charles Lyell (1870)
  • Geological Observations on South America - by Charles Darwin (1846)
  • Geological Observations of Volcanic Islands - by Charles Darwin (1844)
  • Geological Contemporaneity and Persistent Types of life - by Thomas H. Huxley (1862)
  • The Economic Aspects of Geology - by C.K. Leith (1921)
  • Discourses: Biological and Geological Essays - by Thomas Henry Huxley (1894)
  • Town Geology - by Charles Kingsley (1871)
  • The Boy Scouts of the Geological Survey - by Robert Shaler
So, drink one less cup of coffee, relax with a good ole book and be happy!

Thursday, April 8, 2010

Geoscience metaphors (or geo-puns) #2 - "Rock solid"

Oh! parent, parent! send no son to California except he be rock-solid adamant to all vice.  Be her mountains pure gold, let them stand; send no kith or kin of thine to dig them, nor thyself turn towards them, unless armed like an old knight, cap-a-pie, for a desperate conflict, not with revolver and bowie knife, -lead and steel are of small worth, - but with manly principle, a moral coat of mail, light and easy, but impervious.
This is the oldest reference I could find of rock-solid being used as a geoscience metaphor. It is an excerpt from the letter "Straws from the Gold Coast" written on June 26, 1849 in San Francisco and published in the "Daily Southern Cross".  The article also offers an interesting account of what San Francisco was like not even one year after the official start of the Gold Rush:
A timeline from Google News Archive for this geo-pun looks like this:

just follow the link above and chose your favorite rock-solid reference.

In a more recent reference of this metaphor, Joshua Greenman describes his iPad experience with the words "Zippy web browsing, rock-solid feel: New Apple iPad is perfect down to the last micrometer".

One of most famous Romanian rock-solid geo-puns is "tare ca piatra, iute ca sageata", translated as "rock solid and fast as the arrow"; it is part of an ancient Romanian New Year's custom, when kids go around with a stick adorned with flowers and wish the loved ones all the best in the new year.  One can find more info on this custom, which is known as "Sorcova", here.
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