I came across a report on the new year eve of an old problem concerning the fantastic pattern formation and columnar jointing in nature resolved. This particular problem has been close to my heart as I elaborate in the paragraph below hence it was fun to read about it.
A Childhood Story: When I was in grade 2, my pappa got me a set of Childcraft Worldbook. It had some very interesting pictures. I was too young to understand the text completely but I used to love looking at the pictures. There was a very nice picture and a short accompanying article on the Giant’s Causeway in Volume 6 – Our World, on page 31 . However, I enjoyed reading this particular article as it had a story of the kind that kids are attracted to. It said that a lot of people before the turn of the century thought it was made by a giant, Fionn Mac Cumhail, to travel from Ireland to Scotland, and that this explained why the mostly regular hexagonal blocks that made up the Giant’s Causeway were so huge. I was fascinated by the story, but there was a short note at the end – It is believed that these columns were made by volcanic activity. I think fascination is fundamental to most science and art, when talking of science it has to be coupled with its seemingly opposite characteristic – skepticism. I think the line on volcanic activity making the structure did just that. Over the years whenever I saw a picture of the Causeway, I used to wonder how it (specifically the shapes) might have formed. And a PhD student has answered that question now!
The Giant’s Causeway: On the coast of northern Ireland, there is an area of about 40,000 interlocking basalt columns extending into the sea. Most of the columns are hexagonal and fit very neatly, the neatness of this structure inspired a number of legends of an “intelligent designer”.
[A view of the Giant's Causeway on the northern Irish Coast : Image Source]
Click to Enlarge
A structure similar somewhat to the Giant’s Causeway is the Devil’s Postpile in California.
What is known is that in the Paleogene period, there was intense volcanic activity in the region (Antrim), and that it is what formed the structures. However, what was not known was how was it that such specific forms, shapes were formed.
Research: PhD student Lucas Goehring and his adviser Dr Stephen Morris of the department of Physics of the University of Toronto have been working on the problem above. They found out that the size of the columns that varies from one site to another varies as according to the speed of cooling of the lava from an eruption/flow. Using a combination (as required for such a task) of solid mathematical theory provided by Harvard Prof L Mahadevan, good experimentation and field work at the actual sites the researchers solved the problem of what determines the size of the columns.The field work involved making measurements in-situ i.e on the columns to determine at what rate had the lava cooled to form them.
The key to understanding and confirming their ideas was reproducing the phenomenon in the lab, that they did using simple materials. The idea was to use water and corn- starch, which cracks when dried and forms very similar columns as the ones talked about. Controlling the drying rate, a relationship between the size of the columns and the cooling rate was worked out.
The above is the experimental setup for the one just described above. According to Goehring : “The columns are formed as a sharp front of cooling moves into the lava flow, assisted by the boiling of groundwater, As the front advances, it leaves behind a crack network which evolves into an almost hexagonal arrangement. This network carves out the columns.”. They found out that the slower the cooling the much larger the columns.
For more detailed information on the research carried out in this regard, I’d direct you to pages from Goehring’s website.
>> Field Work
He in the above pages gives a quite accessible picture of their findings and their work. Perfect, especially for somebody like me who is not trained in the field in which this research has been carried out, but are very interested in how it was done.
The findings of this work appeared in the December issue of the proceedings of the national academy of sciences.