Tuesday, June 2, 2015
Note: This program first aired May 23, 2015.
This week, for you, a travelogue. Just two days ago I returned from a trip that people keep telling me is on their bucket list. My husband and I spent a week in Iceland, traveling around the countryside experiencing fjords, glaciers, lava rocks, birds and sheep. We soaked in thermal pools, saw mountainsides steaming, and smelled the overpoweringly rank sulfurous odor of boiling mud. Iceland holds a powerful spot in our imaginations, an isolated high latitude island, rife with volcanoes, short on humans, it’s a place we imagine magic can happen. I don’t know about magic, but the landscape is as weird and otherworldly as you think it is, with good reason.
Iceland sits right atop the mid Atlantic Ridge, a mountain chain that results from the Earth’s tectonic activity. 200 million years ago when the continents were bunched together in the super continent Pangea, North America and Europe began to move away from each other, a rift that would eventually form the Atlantic Ocean. As the continents part, new material rises from within the earth to fill in the seam between them. That seam is the mid Atlantic Ridge and as the continents continue to move apart, active volcanism along that seam continues to build sea floor and underwater mountains. Iceland however, isn’t an underwater mountain, it is above the surface and has been since about 15 million years ago. At that time the mid Atlantic ridge drifted over an existing hot spot, which is simply an anomalous plume of ultra hot material from the mantle that circulates up to the crust. Before the seam between Europe and North America drifted over it, this hot spot had been erupting and producing the huge volumes of basalt that make up much of Eastern Greenland, and the northern British Isles. This hot spot, in conjunction with the volcanism of the mid Atlantic Ridge has created enough volcanic material to produce an island, an island that is getting wider by centimeters each year as Europe and North America continue to move away from each other.
On the ground in Iceland what you see relating to all this volcanism is igneous basaltic rock, cooled lava, and ash. Driving along the southern coast you cross wide expanses of what is called sandhur, bleak and desolate outwash plains that result from floods that occur when a volcano and a glacier get together. All the material on this plane is volcanic gravel and sand, which is dark gray or black. Looking in one direction the featureless flatness stretches all the way to the uninviting North Atlantic, in the other direction are steep cliffs or glaciers. Other stretches of road run through lava fields, expanses of rock formed from liquid lava pouring over the landscape and cooled in place. These rounded bubbly formations host a thin skin of green moss, and the effect is a lumpy velvet covered wonderland.
The rock in Iceland is mostly volcanic, and much of that is basalt, a rock type that makes up most of the sea floor. When basalt cools from a liquid to a solid in the right circumstances, it will form columns, usually hexagonal but sometimes other shapes as well. Those columns are embedded in bed rock, so they don’t mean much to us until erosion happens and they are exposed. Iceland has lots of exposed basalt columns, columns with waterfalls going over them, columns in beachside cliffs, columns visible virtually anywhere rock is exposed.
All this volcanic activity and thin crust means that there is a lot of heat around, heat from inside the Earth. Iceland also has a lot of water, both in the form of precipitation and held in glaciers. And heat coming out of cracks in the earth, plus ample water equals one of my favorite things, hot springs. The island is criss crossed with pipes carrying hot water for municipal purposes, home heating and domestic use, electricity generation and most importantly for this traveler, geothermal pools.
Lava fields, desolate black sand beaches, columnar basalt, geothermal pools-it’s a landscape very different from my normal one but that is what traveling is for-to take us out of our normal experience and engage us in what is novel. The best travel stimulates reflection and forces you to rectify what you know with what you are seeing. I’ll share more of what I was seeing in Iceland next week.
General reference on Icelandic geology, from the University of Rhode Island http://www.gso.uri.edu/lava/Iceland/Iceland.html
Hot spring smell, explained: http://hotspringsguide.net/why-do-some-hot-springs-smell/
Icelandic Institute of Natural History http://en.ni.is/
Great well kept up blog of current events in Iceland geology: http://www.jonfr.com/volcano/
A student project on the geology of Iceland, nice images and references: http://academic.emporia.edu/aberjame/student/brown3/iceland.htm
Nice overview of Icelandic geologic history, including funky translation: https://www.extremeiceland.is/en/information/about-iceland/history-of-iceland
On columnar jointing in basalt http://volcano.oregonstate.edu/columnar-jointing