Iceland revisited

I'm well into my travels in France (1 month now) but as I promised in an earlier blog, I wanted to share with you what I've learned about tectonic plates, in particular, the two significant plates that meet in Iceland. Try to stay awake.

As you will remember from high school geology, the earth's crust is a bunch of adjoining plates, much like the shell of a turtle. Unlike the turtle shell, these plates are in constant motion in all different directions. Most of the major earthquakes and volcanoes occur where these tectonic plates meet and each seam exhibits one of three types of motion.

Transform Slide slipping – where the plates grid past each other as we have in California. Friction causes pressure to build until there is a sudden slip or earthquake.

Convergent boundaries - occur when two plates move towards each other resulting in mountain ranges like the Andes in South America.

Divergent boundaries - are those that move apart, which is what you find in Iceland. What is most unique about Iceland is that it is the only place on earth where a divergent boundary is above sea level and thusly more easily observed.

The boundary, called the Mid-Atlantic Ridge, passes from the southwest to the northeast corners of Iceland. The plate to the west is the North American Plate while the other is the European Plate – and these two plates are moving apart at the astonishingly rapid rate of 3 inches per year. "Astonishingly" is a relative geological term.

At one location in the southwest corner of Iceland, there is a very pronounced valley that clearly shows this line of separation. The valley is only 50 meters wide, maybe 10 meters deep and a half-mile long. A small footbridge has been built there and spans this gap and the two ends of the bridge are not permanently attached. In the middle of the bridge is a sign with a line showing the exact location of the two plates.

Because of this divergent movement, the earth's crust is thinner in Iceland which gives rise to lots of volcanoes and geysers in Iceland. In fact, there is a town in Iceland named "Geyser" which is the generic name used all over the world. This thin crust also means that thermal wells are easily accessed and the steam from those wells generates 90% of the country's electricity.

 

Most of the geology in Iceland is relatively new, quite jagged with little erosion except in the valleys where glaciers have eroded the terrain.  

Class dismissed.