So of course I wasn’t going to write about primary igneous structures and Ireland with out covering the Giant’s Causeway.
This is probably Ireland’s most famous geologic feature and a place I’ve wanted to visit ever since I was just a wee intro student.
These columns, located in Northern Ireland, are part of a cenozoic aged tholeittic basalt unit which erupted on the surface about 60 million years ago.
Photo by Aaron B.
Here are some of my fellow field students, probably discussing something like how they were going to pull off recreating a man-sized version of the famous Led Zeppelin shot from the album cover to Houses of the Holy. ( no, really)
These columns form as the basalt cools and contracts creating the hexagonal shape. I wrote about some columnar basalt in the Blue Ridge Province of Virginia last spring, which are much older. But of course they really cant compare to the Giant’s Causeway.
Most of these have 5 or 6 sides, although I have been told there are 7 or even 8-siders to be found. I spotted only a few 7-siders, but nothing greater.
Like this one.
And this one.
Here is a view of the columns from the side along with myself proudly displaying my shirt from Citizen Chain, my good friends and the very best bike shop in San Francisco, maybe even the world.
Another student, making his way across the columns.
Maybe this is something that can be explained by weathering, or maybe is the result of a varied cooling front.
For more on cooling fronts and such, here is a link to my former structural geology professor Callan Bentley’s great post on cooling fronts and column formation.
Here is one more shot of Ireland’s iconic igneous structures.