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.
References:
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
