Constant quakes: Life on the edge (of a divergent plate boundary)

The image at left represents all of the earthquakes in Iceland in the last 48 hours as of the writing of this article. Can you guess how many there were? 15? 37? 111. Icelandic Seismicity While that may seem incredible, for contrast there were nearly twice as many in California in the same time span. USGS Earthquake tracker Most of these quakes are very small, less than magnitude 1, and are not dangerous. But the Earth's surface is in a constant state of change. Earthquakes are our evidence of this. In a place like Iceland, where a tectonic plate boundary is a defining feature (really THE defining feature in Iceland) nothing less than constant seismic activity can be expected. The reassuring news for the people of Iceland is that a divergent plate boundary is the least likely to produce a lethal earthquake.

 (at left: Image of ground movement in a strike-slip fault)

In a strike-slip fault where two plates slide past each other, like the San Andreas in California, energy is built up over decades or centuries as  the two plates attempt to move past each other. In a divergent plate boundary, (like the one under Iceland) the plates moving away from each other are less capable of storing energy before releasing it in earthquakes. This isn't to say that Iceland goes unprepared. University of Iceland: earthquake research projects They have an extensive emergency response network, trained and ready to deal with earthquakes as well as volcanic eruptions. Icelandic civil protection bureau Iceland as a nation also has one of the strictest building codes in regards to their resistance to seismic motion. Details on Icelandic earthquake-proofing I think it's safe to say the Icelandic people have a very real understanding of, and practical and extensive approach to, the natural hazards of their island.

 

 Iceland: A country divided...

Iceland is being pulled apart! Literally! Not to worry though. These tensional forces are what gave birth to the island in the first place. Iceland sits directly astride a divergent plate boundary. Divergent boundary definition. This type of tectonic boundary is where two plates are pulling apart from each other. We call the one that Iceland is on top of the Mid Atlantic ridge. The gap left by the spreading crust at a divergent boundary allows magma to rise closer to the surface and burst forth as lava much more easily, and more frequently. This is the reason for Iceland's frequent volcanic eruptions. It also accounts for why Iceland experiences mostly fissure eruptions, which are eruptions along a linear opening, rather than the cone shaped volcanoes we think of from childhood. The most recent eruption on the island was of this type. Fissure eruption in late 2014.

    At left; The blue line represents where the Mid-Atlantic ridge passes through Iceland. The red dot represents the area of the most recent volcanic activity.

Iceland is a country that makes very efficient use of it's limited natural resources. In 2013, 99% of it's electricity for example, was produced by a combination of hydroelectric and geothermal plants.
Icelandic Power Authority: Icelandic generation of electricity
It's mineral resources however, are almost negligible. While Iceland has begun producing aluminum in recent years, with several large-scale smelting factories being built in the last two decades, The bauxite (ore that aluminum comes from) is not mined in Iceland. Foreign metal companies (one of the largest being Century aluminum co, of Monterey California) have been attracted here by the cheap electricity costs due to the abundant sources of hydroelectric and geothermal power. The icelandic people are not entirely pleased about this foreign investment however. Read the LA times article here:Iceland divided over foreign aluminum companies. Iceland does produce some cement and pumice USGS: Iceland's mineral production from it's igneous rock, but the country's only native mineral resource is something called diatomite.
Diatomite is an organic mineral formed by algae called diatoms. It is actually the silica-based exoskeletons of these tiny creatures. While microscopic individually, they form substantial deposits when they collect over many generations. (think of coral reefs!) Diatomite has many and quite varied uses. Everything from a mild abrasive in toothpastes and soaps to a natural insecticide. (feed some to your pets to keep them pest free, no kidding!) All Icelandic diatomite comes from only one source, a lake called Lake Myvatn. This lake provides the perfect habitat for these diatoms to live and thrive due to it's proximity to volcanic heat sources.






above: a sample of diatomite
Right: a diatom under magnification

Iceland is a country in which geologic processes play a large part in daily life. The most common natural hazard is volcanic eruptions. These are a very regular occurrence here, almost constant when looked at in geologic time scale. There was a major eruption going on as recent as late 2014, beginning in August and lasting through september. Read the Newsweek article Here. Balanced against Iceland's volatile geologic activity is it's relatively small population. The island, which is roughly the size of Massachusetts, boasts a population of just over one quarter of a million people. The population has only risen even to these modest numbers in the last half of a century. On top of this, most of the population is concentrated in a small area near the capital city. This is a key factor in how generally harmless Iceland's natural hazards are. A natural hazard is a natural occurrence which threatens the lives or property of humans. There are generally no people, and is no property, around to be damaged. A striking exception to this general rule was the eruption in the Vestmannaeyjar islands off the coast of the main island in 1973. A fairly dense population on the island of Heimay led to over 400 homes being destroyed when that island's volcano opened lava fissures and spewed hundreds of tons of lava onto the island's one village. This eruption left over 700 people homeless, making it one of the worst natural disasters in the country of Iceland's history. A natural disaster is how we classify a natural hazard that has caused significant disruption of human activity, or loss of life. If a natural disaster reaches a certain scale, in terms of damage and loss of life, it becomes classified as a natural catastrophe. To Iceland's credit, the danger of experiencing a natural catastrophe is fairly low. There is simply not a large enough population density in any of the danger areas of the island.

Welcome to Thingvellir, the ancient meeting place of the Icelandic people. It is itself an incredibly interesting geologic feature, endemic of Iceland's tortured geologic history, present and future. The area known as Thingvellir is a large flat plain with steep walls on either side. Unbeknownst to the ancient Icelandics who choose this spot for it's natural beauty, Thingvellir is actually the inside of a tectonic fissure. The plain is increasing in size as Iceland is gradually pulled apart across the European and North American tectonic plates.