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, 1783

Mitigation-

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 barrier 
pictured 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.

Coastal Processes in Iceland

Iceland, as a whole, is growing. The near constant vulcanism on the island adds more and more land, almost every year.
The existing land is also uplifting. Pressure from large ice sheets is being removed as glaciers here recede due to global warming. The crust is rebounding, like a sponge that is compressed and then released. This uplift is outpacing sea level rise. In some areas there is 35mm/yr of uplift vs. 3.2mm/yr sea level rise.    
Iceland's rebound  vs. sea level increase. This change in height is having a dramatic effect on the erosion of these areas of Iceland's shores. Contrary to what you might think, the rate of erosion is decreasing due to the uplift. There is a mathematical rule, known as The Brunn Rule of Erosion (Brunn, 1983) which states that if sea-level rises by (a) there will be coastal erosion (s) equal to:
   s = la/h . (h) equals the maximum depth of exchange of material between the nearshore and offshore, and (l) is the length of the profile of exchange. Iceland's rebound is equal in effect to a decrease in the sea level. In areas of the southeast coast of the island, which are experiencing the most dramatic uplift, erosion has equaled approx. 8m/yr over the last century. in other areas which are not being uplifted, the erosion is closer to 10m/yr. Coastal Erosion Near Jökulsá River.

Despite this small bright spot, the changes brought about by the melting glaciers are not positive. An increase in the flow of the rivers which carry glacial melt to the sea is causing those rivers to erode more of the coast. River deltas are being pushed further and further inland as more powerful currents remove sediments more rapidly. The main component of these deltas is clastic material washed down the glaciers from past eruptions.





Near the town of VÍk the last major eruption, that of the volcano Katla, happened in 1918. The washout from this eruption extended the coastline by approx. 5-6 hundred meters, from 1918 until 1971. Since that time the shore has re-eroded 350-450 meters (an average of 11.25m/yr), and is as about the same as it was before the eruption.
 (at right: VÍk's shoreline from 1904-present)
Sediment transport off Iceland's shore.

The Icelandic people are not sitting idly waiting for calamity to strike. There are seawalls, dykes, and beach replenishment projects going on all over the island. coast adapt report They have established what they call a "defense line", sea defense structures in an area still inland enough that several decades of predicted erosion will pass before the sea will be in contact with this "line".

Extreme Weather In Iceland: 

Wind Storms- 

Wind storms are common in Iceland. Storms there can often reach speeds in excess of 60 m/s. Extreme weather in Iceland. These storms rarely cause any significant damage on their own. Some secondary effects of these storms however are sea flooding and avalanches.

Iceland is kept warm by a branch of the gulf stream current that flows past the south and west shores. This warm current is Iceland's lifeblood, the reason the island enjoys warmer temperatures then it's northerly position might indicate. This does however create areas of pressure difference above the island, with cold air being drawn from the arctic to a low pressure center off of Iceland's east coast.  Iceland's average weather statistics.  These conditions feed high wind development across most of the island.

Snow storms-

Iceland does suffer from daunting, if not quite devastating, snowstorms. High winds and high levels of snowfall can cause massive transportation problems and cause people to remain in their homes for days at a time.  Snow storms in Iceland

Cyclones-
Extratropical cyclones are not unheard of in Iceland. The near constant area of low pressure on Iceland's east coast, the "icelandic low" as it's called, very regularly causes extratropical cyclones to form there, and sometimes make landfall on the island Icelandic cyclones

Subsidence in Iceland, a strange relationship.

Iceland doesn't have to worry about subsidence. Well, not in the usual sense. Soil subsidence is the movement of surface material, generally due to a change in conditions below the surface. A thick layer of soil above limestone, for example, can produce large movements of surface material, including sinkholes, when the underlying limestone is dissolved by weakly acidic water. Iceland has very little sedimentary rock (8-10%), and no large areas underlain by soluble rock. Rock history of iceland. The subsidence Iceland does have to worry about however, relates to volcanoes.

The image above is of the massive Bárðarbunga eruption from 2014-2015. This volcano erupted continuously for five months, from Sept. 2014 to Feb. 2015. In this time, and in the time since, the area inside of Bárðarbunga's caldera (the opening of the volcano) sank over 35 meters (115 feet) as the magma chamber emptied itself into a massive lava field on the surface. Detailed report of Bardarbunga caldera subsidence. The total subsidence for this event (the detailed measurement did not begin until the event had already started) is estimated at nearly 60 meters. The graph below shows this subsidence from Sept.-Mar. The eruption ended in mid February, and you can see that as the subsidence ceased, the line reversed very slightly. This shows that almost immediately upon cessation the magma chamber began to fill again.

Measuring the swelling or subsidence inside of volcanoes is a valuable tool for geologists trying to predict the health or volatility of a volcano. Subsidence during an eruption is self explanatory. If your volcano is subsiding with no visible eruption however, you must look for another reason, either that there is an eruption somewhere you can't see (such as into the sea or underground) or that the flow of magma which filled that chamber has gone elsewhere. If the flow of magma into a particular chamber does cease, a total collapse of the caldera may occur. This happened to the caldera of the Askja volcano after a massive eruption in 1875.  Askja caldera collapse. This particular event took over 40 years, and as such was not very dangerous, but a sudden collapse is possible and would pose a danger to any scientists unlucky enough to be studying the area at the time.

Mass Wasting, in it's many forms:

"Mass wasting" is a general term most people are unfamiliar with, but who's effects are very well known. Mass wasting is defined as "any type of downslope movement of earth materials." This can include land/rock slides, avalanche, or earth flows. Whatever the material involved, one constant in all of these events is a slope. Iceland is a very mountainous island. A large percentage of these slopes consist of loosely compacted volcanic materials. In addition, Iceland has significant snowfall in it's higher altitudes. These facts together mean that Iceland's most common forms of mass wasting are rock/land slides, and avalanches.

Landslide

Iceland suffers from landslides on a fairly regular basis. There was a significant slide into the caldera lake of the stratovolcano Askja in July of 2014, pictured here. 

While there was no loss of life, this slide was the largest recorded since the settlement of Iceland. Estimates place the volume of material displaced at 30-50 million cubic meters. Not all of this material went into the lake, but enough did to create a 20-30m (60-90ft) high tsunami all around the lake. Report on the Askja Landslide . It was very fortunate that this slide took place shortly before midnight, as people certainly would have been using the lake in daylight hours.


While a landslide may appear to humans to be a sudden, unpredictable event, this is not the case. Photographs from this and other slides show a gradual movement of large volumes of material over the course of years. This sudden movement was merely the culmination of many long years of instability. Any hillside should be treated as potentially hazardous, as all slopes are subject to the effects of gravity, and as such are always on their way down, to one extent or another.

Avalanche

 

As with any country with heavy snowfall and steep slopes, Iceland faces significant danger from Avalanche. Avalanche are caused by several factors in the snow. Sudden warming of snowpack on a slope can cause the upper levels to melt and saturate the lower layers with water, increasing the weight of the snow until it can no longer maintain it's position on the slope. Sudden rain onto existing snow will have the same effect. Wind blowing large quantities of snow onto the downwind side of a slope over a short time will also cause the mass of snow to become too great to maintain it's "angle of repose", the angle at which a mass can remain stationary on a slope. Avalanches are most common on slopes between 35 and 40 degrees. Grades below this lack the momentum necessary to create a dangerous flow, and grades above this tend to allow snow to constantly slide off. 

Read The Iceland Meteorological Office's section on avalanche here:

Danger Mitigation

Iceland recently commissioned a comprehensive study of all areas of avalanche risk. Iceland's Avalanche risk survey winds to a close. This initiative was started after two 1995 avalanches killed a total of 34 people in two towns in northern Iceland.  These tragic events highlighted both the underrated risk of avalanche in some areas of the country as well as the lack of preparedness for dealing with such events. After significantly increasing the collective knowledge of the Icelandic scientific community's understanding of avalanche risk and successfully developing a risk map and warning program for the island, the leftover funds from the assessment program are being redirected to increased mitigation of the effects of possible volcanic hazards.

Icelandic Tsunami: unexpected danger

 It might surprise you to learn that Iceland experiences flood waves, or tsunami fairly regularly. Icelandic Met office tsunami hazard assessment The government is as aware of the eventuality of another tsunami as it is of the potential for volcanic eruptions. Iceland actually has two causes of tsunami to fear. Both the immense power of a sea-borne tsunami that any nation with a coastline (particularly an island) faces, as well as inland tsunami, caused by rapid flooding. A sea-borne tsunami is much less likely, although still a very real possibility. The only recorded tsunami wave to reach Iceland's shores happened in 1755, and was caused by an earthquake near Lisbon, Portugal. While this earthquake and tsunami caused significant damage along European coasts, even as far as Ireland, Iceland is quite far away and the wave had lost most of it's power before striking the island. Tsunami risk-appraisal for Iceland. Tsunami are most often caused by earthquakes at subduction faults. Iceland's location atop a divergent fault, and it's distance from any subduction zones, means there is less chance for one of these devastating waves coming from the sea.

Of the two, Iceland is more at risk from this second type due to the nature of it's glacial volcanoes. These inland waves are caused by what the Icelandic people call a Jökulhlaup, a flood caused by a volcanic eruption under a glacier. This video shows the resulting Jökulhlaup from the famous 2010 eruption that halted all air traffic in Europe. Video of glacial flood.

Iceland: Volcanic jewel in the ring of fire

Iceland is known as "The Land of Ice and Fire". With a name like Iceland, and it's location near the arctic circle, the ice part might not come as a big surprise. The "fire" nickname comes from Iceland's extensive volcanic activity. Iceland is straddling a divergent plate boundary in the ring of fire called the Mid Atlantic ridge. It is also traveling over a "hot spot" in the mantle, the layer of the earth below the crust. Volcanic History of Iceland. A volcano erupts in Iceland every 3 years, on average.



 The divergent plate boundary accounts for the fissure eruptions (as seen at the right from the 2014 Holuhraun eruption) which are very common on Iceland.









The hot spot, or "plume" in the mantel is responsible for the more classically cone shaped volcanoes, and high volcanic mountains on the island. Kerlingarfjoll: Rhyolitic cinder cone
Snaefellnes: Rhyoltic cinder cone. A geographic position just outside the arctic circle causes glaciers to form on the slopes of these volcanoes. This combination of "fire and ice" is one of the most common features in iceland. These rhyolitc cones are much more dangerous than the fissure volcanoes. The type of magma which erupts from them is much more viscous, or thicker. The additional weight of the glacial ice that forms on top of them also compresses and delays eruptions, making them more violent and explosive.



This also causes extensive flooding when a sub-glacial eruption happens. While Iceland has an eruption warning system, it places much more importance in it's Flood warning system. The volume of water discharged in one of these floods can be greater than that of the flow of the Amazon river.





This combination of volcanic features gives Iceland it's unique terrain. Hot spots alone generally form island chains like Hawaii. It also explains why there is such a high volume of volcanoes on such a small island.