Iceland's comprehensive hazard report
Iceland is a land of extremes. Perched atop a divergent plate boundary, lying at the edge of the arctic circle, and isolated in the north Atlantic, Iceland is a perfect summary of our world in motion. A land in a constant state of flux. A place where geologic time becomes understandable, even evident, to the human mind. Iceland is not THE most dangerous place to live. Statistically speaking, you are much more likely to suffer misfortune due to natural events in Japan, or in many parts of the United States. Iceland is, however, a very volatile and potentially dangerous island. There are hazards here which must be taken into account if a human population is to continue on the island. Much of this is due to forces beyond human control, the location and nature of faults, geographical position, etc. But much is also due to the nature of human settlement. The most dangerous areas also tend to be the most beautiful, and so humans put themselves in danger. Iceland's greatest hazards come from both it's geological position (it's proximity to a fault) and it's geographic location (near the arctic circle). Specifically, The greatest threats to the human presence on the island are volcanic eruption, and avalanche.Volcanic Eruption
A volcanic eruption creates multiple distinct dangers. In this report I will discuss each facet as a separate issue, and then discuss mitigation strategies for an eruptive event as a whole.Tephra-
The material ejected from an erupting volcano is collectively known as tephra. This includes volcanic ash, pieces of existing rock pulverized in the explosion of the initial blast, and lava bombs (magma that cools as it is in the air and often explodes upon contact with the ground). Tephra can be extremely dangerous for humans. Larger pieces of tephra can be fatal when they crush either homes or individuals. Volcanic ash can also bury entire cities, as happened to the Italian city of Pompeii. A large percentage of Iceland's volcanoes are rhyolitic or andesitic stratovolcanoes with the potential for extensive ejection of tephra at significant distances (40+ km). Any humans predicted to be within the fallout zone of such an eruption should heed the warning to evacuate. In three of the historically recorded eruptions of one of Iceland's most notorious stratovolcanoes, Hekla, tephra from the eruption covered 80% of Iceland. holocene eruption history as evidenced by tephra layers The last of these significant eruptions occurred in 1104 B.C. If a similar event were to happen in the future (as it is bound to) there would be significant loss of life and damage to property without drastic evacuation programs.Lava/Pyroclastic Flows-
A lava flow is a downslope movement of molten rock produced in a volcanic eruption. Most eruptions do produce a lava flow to some degree, though to what degree can vary greatly based on the viscosity and composition of the lava being erupted. The most recent eruption in Iceland which began in August of 2014 and ended in February of 2015 produced a new lava field larger than 85km/sq, (33sq mi). Holuhraun eruption aftermath. The only thing which can prevent damage from a lava flow is the absence of human settlement in the area, which luckily was the case here. The fact that most areas in danger of being inundated by a lava flow are uninhabitable is a blessing for Iceland. A pyroclastic flow is slightly more complex than a lava flow, though may contain lava as well. A pyroclastic flow occurs when the volume of tephra ejected by an eruption supersaturates the air, or a large volume cools and coalesces to the point that it can no longer remain aloft. The end result is the same, and a cloud of volcanic material collapses to the ground and continues downslope, picking up anything in it's way, including ash, lava, lava bombs, and rocks up to boulder sized. Needless to say this is one of the most spectacular and devastating dangers of a volcanic eruption. It generally takes a large and violent eruption to produce a pyroclastic flow, so is not very common. However, pyroclastic flows create a particular type of rock, called ignimbrite, when they form. ignimbrite near Katla in Iceland These rock formations are present in the tephra records of several of the most volatile volcanoes in Iceland, so it can be deduced that these events have happened before, and will again.Toxic gasses-
Largely overlooked in our imaginations, toxic gasses are actually one of the most consistently lethal consequence of a volcanic eruption. Capable of spreading clouds of SO2 (sulphur dioxide) and other gasses over areas of thousands of miles. In the eruption of the volcano Laki in 1783, most of Europe and some of North America were covered by a sulphuric haze which weakened the sun for around 5 months. Thousands died, both in Iceland and in mainland Europe from acute sulphur poisoning as well as from famine caused by the death of crops and livestock affected by the gases. This danger is unavoidable if an eruption of this scale happens again, which it almost certainly will. SO2 output from Laki, 1783Mitigation-
Iceland is already on the right track. As a nation, they realize how precarious their position is on this volatile island. I agree with them that living there is worth the risk. This ruggedly beautiful land is more fascinating than any I could imagine. the key is to minimize the danger presented to the people living there while maintaining a normal standard of living. My recommendation is to continue to staff a well funded and extremely competent geological survey, which is already in place. iceland geosurvey. Volcanoes are slightly more predictable than some other natural hazards such as tsunami, violent storms, cyclones, etc. This allows for a longer than average preparation time as long as rigorous scientific measurements of active volcanoes are kept. Iceland also has a world class meteorology office. Iceland Met office This is the main channel for disseminating disaster information. They have gone into action before, and performed phenomenally. This office shares information about sulphur clouds and magma chamber swell the way other nation's weather services talk about the day's temperatures or rainfall. All of these can help to alert people in danger areas, and for 90% of eruptions will be more than sufficient. But, in the event of a lethal and sustained SO2 emission, or an eruption with significant ash fall, total evacuation is the only solution. Iceland's volcanoes, relative to their magma chamber and cone sizes, have the potential to be lethal to most life on the island. An eruption of this scale is not in the lithological record, but it is nonetheless possible. I believe an agreement with another nation to take in the entire island's population as refugees is the only way to guarantee the safety of every Icelander. Iceland has close cultural ties with many of the Scandinavian nation's, in particular an almost 1000 year history with denmark that could be taken advantage of in this instance.Avalanche
From a statistical standpoint, avalanche are the second deadliest natural hazard on Iceland. There are some hazards with the potential for much greater damage and loss of life, such as glacial floods. However, the location of such events far from people and their rarity makes them much less practical to plan for. An avalanche is any downslope movement of snow and ice. Resting between 20-35 degrees of inclination, captive snow has a great potential to begin moving with even a very slight change in atmospheric conditions, temperature, or humidity. Given Iceland's position at the edge of the arctic circle, snow has an extremely long season, particularly at higher elevations. The island also has extremely mountainous terrain. These features combine to make Iceland's remote mountain villages particularly susceptible to avalanche. In the 20th century alone, 193 persons in Iceland died from avalanche.avalanche deaths Many of the remote yet habitable area in Iceland lie in valleys between volcanic mountain ranges. This presents an immediate problem because there is little space in these valleys, and all of it has the danger of being covered by an avalanche, if one of a certain size happened.Avalanche danger mitigation-
The most sure way to avoid the danger of an avalanche is simple. Do not build in the shadow of mountains. This same rule applies for all mass wasting. Material eventually moves downslope, whether it be snow, soil, rock, or anything that happens to be on top of the slope. All material is affected by gravity and is trying to bring itself to rest on a flat surface. Being realistic though, it is understandable why a mountain valley is a desirable place to build a home. Stunning beauty surrounded by mountains, ample recreational opportunities on ski slopes and in mountain lakes, and the fertile soils brought down from the mountains are all reasons why humans are unlikely to cease building in danger zones anytime soon. So, the best mitigation strategies involve diversion or prevention of movement. Material moves downslope along the path of least resistance. If you can engineer a pathway for such material away from any settlements, such as by digging trenches or valleys into a mountainside, you can direct material safely away from danger zones while making as limited of an impact on the natural processes of the area as possible. This sort of project is incredibly costly, and is a serious engineering undertaking, making it somewhat prohibitive in modern economic terms. The more feasible option are snow dams, barriers constructed parallel to a slope that allow snow (any any other material for that matter) to fall a certain distance but no further. As with all manmade attempts to defeat nature, these systems are not 100% effective. If an event of a certain size occurs, your barriers become ineffective as the volume of snow is larger than they can contain, or such force is released that the barriers themsleves are breached. However, several of these systems are already in place in Iceland, and have been used to satisfactory effect.One such barrier exists near the town of Engihlíð and stopped a major slide in 2012. avalanche barrierpictured below is the avalanche dam system mentioned in the story, with the horizontal black lines representing the dams, and the extent of the slide outlined in red.
Building site
One of the most important considerations taking into account the geology of an area is answering the question "where is it safe to build a home?" In Iceland, there are not many clear answers. The island is largely covered by volcanic mountains, which represent danger on their slopes from volcanic eruptions, as well as in the valleys, from landslides and avalanches. The flat, low lying areas of the island are generally washout plains of glacial floods and volcanic material. Curiously, the capital city, Reykjavik, is situated in one of the safest areas on the island. It stands well outside of the volcanic zone, and is a safe distance from any mountainous areas. The only danger that it will face in the near future is from inundation, as Reykjavik is a coastal city, and stands more or less at sea level. For these reasons I would build my home in the northern section of the island, far enough from the sea to avoid the danger of rising sea level, outside of the volcanic danger zone, and upwind of most of the historically violent volcanoes. There is a semi-permanent low pressure area off of Iceland's southeast shore which draws air in a southeasterly direction. When toxic gases are emitted from volcanic eruptions, they generally travel southeast with these winds and travel to mainland Europe. While building here is no guarantee of safety, I believe building a home in this area is the most likely place to be safe for my lifetime, and more importantly, be safe for future generations.
