Week 9: Subsidence in Iceland

 

Subsidence is a sinking of the ground due to underground material movement. Its causes can include human interference (anthropogenic subsidence) such as removal of water and natural resources such as oil and natural gas  from the ground by means of pumping, fracking, or mining. Subsidence can also be caused by naturally occurring events including earthquakes, soil compaction,  glacial isostatic adjustment (GIA), erosion, and sinkhole formation.  It can happen anywhere in the world and it does happen in Iceland but is rarely a problem for humans due to the fact that Iceland is proactive about where they build and the country is quite sparsely populated.  

Iceland is a country that is constantly deforming.  Subsidence in this country has a number of causes such as plate spreading, GIA, volcanic, and geothermal processes. GIA is the ongoing movement of land in response to the last ice age. The following explanation from NOAA made it very clear for me so I am quoting it below in the hopes that you will also find it helpful:

Here's how it works: Imagine lying down on a soft mattress and then getting up from the same spot. You see an indentation in the mattress where your body had been, and a puffed-up area around the indentation where the mattress rose. Once you get up, the mattress takes a little time before it relaxes back to its original shape.

Even the strongest materials (including the Earth's crust) move, or deform, when enough pressure is applied. So when ice by the megaton settled on parts of the Earth for several thousand years, the ice bore down on the land beneath it, and the land rose up beyond the ice's perimeter—just like the mattress did when you lay down on and then got up off of it.

GIA is the main source of vertical deformation in Iceland while plate spreading is the main source of horizontal deformation.  

Iceland has long made use of the geothermal waters in this country so an anthropogenic cause of deformation in Iceland occurs around  the Reykjanes, Svartsengi, Hellisheidi geothermal power plants as well.  

A photo of an “ice cauldron” at Bárðarbunga caldera, which scientists have surmised have probably formed due to volcanic, or geothermal activity below the surface. 

As far as mitigation measures are concerned, the Icelandic Meteorological Office constantly shares updates with the public.  The government also uses seismic monitoring, satellites,  and GPS systems to monitor the  degree of subsidence.  In addition, as I stated earlier in this post, the country is selective about development and is not a very populous country which also helps in this regard. 

Finally, I would like to share this relatively new bit of land in Iceland.(see photo below)  This piece of land is temporary as it has already experienced a great deal of subsidence, but I found it very interesting. 

Above is a picture of Surtsey Island, which was created in a 1960 volcanic eruption. It is located on the southern coast of Iceland.   Already the island has shrunk to half of its original size due to subsidence and erosion.  Scientists predict that it will sink back below the surface sometime after the end of the current century. 

Sources:

Researchgate

https://www.researchgate.net/figure/Subsidence-in-Reykjanes-RNES-and-Svartsengi-SVAR-estimated-from-GPS-measurements_fig4_284578691

Visit Iceland

https://www.visiticeland.com/article/unesco-world-heritage

NOAA

https://oceanservice.noaa.gov/

Week 8: Mass Wasting in Iceland

Landslide in Reyðarfjörður – Photo by Halldór G. Pétursson

Mass Wasting  is very common in Iceland, due to the terrain and a number of contributing factors, such as interaction between climate, lithology of the region, and soil erosion.  Although gravity alone can be responsible for a landslide, there are also a number of triggers in Iceland.  These triggers include: intense rainfall,  melting and retreat of the frozen landscape, changes in groundwater currents, seismic activity, and the undercutting of the land by ocean waves and glaciers. The highest landslide risk in Iceland occurs during seasonal low-pressure systems that happen in the fall bringing heavy rainfall and wind, and from the spring snow melt. 

Extent of the largest landslide where it entered the sea

.(Photo: National Commissioner's Special Forces)

     Quite recently, a landslide in Seyðisfjörður  occurred in December 2020.  This was the largest landslide to have damaged an urban area in Iceland. Fortunately no lives were lost in this event. (See photo above and outlines below)

Outlines of the December landslides in Seyðisfjörður, eastern Iceland.

There are a number of types of landslides that occur in Iceland including rockfalls, mud or debris flows, earth flows, rock slides, and gradual creep. They occur in all regions of Iceland but mostly in Central North Iceland, the East Fjords, and the West Fjords. 

Mitigation efforts are centered mostly on land use planning and creating "no build" zones. Experts are also researching the creation of better monitoring systems and the possibility of building mudslide barriers above towns that may be in danger of landslides. According to the Icelandic Meteorological Office, " Althingi ‒ the national parliament of Iceland ‒ recently approved a five-year budget plan, increasing government funding for the construction of avalanche defenses by 1.6 billion ISK annually."  Hopefully this will help expedite the creation of these defenses and increase safety for residents and tourists alike.  

  Sources:

Icelandic Meteorological Office (IMO)

https://en.vedur.is/

Icelandic Institute of Natural History

https://www.ni.is/

Week 7 Flooding in Iceland

   Iceland is a fairly large island situated in the middle of the North-Atlantic ocean, just south of the Arctic Circle, between 63.4°N and 66.5°N latitude. Iceland is a country that has a medium risk of coastal flooding, according to Thinkhazard.com. In order to deal with this issue before a flood, the government of Iceland has taken a number of  measures.   Building projects, including planning, design, and construction methods,  are to take into consideration the level of coastal flooding hazard in a given area and proceed accordingly. 

     “Coastal flood risks are defined by water levels and water velocity. The levels determine how much of the building from the ground up is exposed to potential damage. Water velocity is often discounted or entirely ignored although it is often responsible for as much or more damage than water contact alone. As with wind, rapidly moving flood waters can carry large and heavy debris that upon impact can cause direct physical damage. Soil scour within fast moving water can penetrate the building envelope and lead to expensive clean up costs. Be mindful of these risks by evaluating surrounding land use and potential land development in the vicinity of your project area.” 

    Iceland is unique in that there are many glaciers situated directly on top of geothermal activity which can melt the glacier and  can result in glacial flooding.  This can have disastrous effects and result in a mega flood called a  Jökulhlaup which has threatened people and damaged large areas of land impacting agriculture and livestock. The most recent one occurred between November and December 2021 which is pictured below:

The water level rose substantially in the Gígjukvísl river between 28 November (left) and 1 December 2021 (right) from the jökulhlaup that began on 24 November draining the subglacial lake at Grímsvötn. View is to the S from the IMO webcam. Courtesy of IMO.

The National Weather Service gives the following information regarding what to do before a flood:

Sometimes floods develop slowly and forecasters can anticipate where a flood will happen days or weeks before it occurs. Oftentimes flash floods can occur within minutes and sometimes without any sign of rain. Being prepared can save your life and give you peace of mind.

–Create a Communications Plan

It is important to be able to communicate with your family and friends in the event of a disaster. Whether it is having a specific person identified to contact for status updates or a safe location to meet up with family members, having a plan in place will give you peace of mind if disaster does strike.

–Assemble an Emergency Kit

It is good practice to have enough food, water and medicine on hand at all times to last you at least 3 days in the case of an emergency. Water service may be interrupted or unsafe to drink and food requiring little cooking and no refrigeration may be needed if electric power is interrupted. You should also have batteries, blankets, flashlights, first aid kit, rubber boots, rubber gloves, and a NOAA Weather Radio or other battery operated radio easily available.

–Know Your Risk

Is your home, business or school in a floodplain? Where is water likely to collect on the roadways you most often travel? What is the fastest way to get to higher ground? Knowing the answers to these questions ahead of time can save your life.

–Sign Up for Notifications

The Advanced Hydrologic Prediction Service provides RSS feeds for observed forecast and alert river conditions to help keep the public informed about local water conditions

–Prepare Your Home

Sometimes floods develop slowly and forecasters can anticipate where a flood will happen days or weeks before it occurs. Oftentimes flash floods can occur within minutes and sometimes without any sign of rain. Being prepared can save your life and give you peace of mind.

1. If you have access to sandbags or other materials, use them to protect your home from flood waters if you have sufficient time to do so. Filling sandbags can take more time than you may think.

2. Have a professional install check-valves in plumbing to prevent flood waters from backing up into the drains of your home. Make sure your sump pump is working and consider having a backup. Make sure your electric circuit breakers, or fuses, are clearly marked for each area of your home.

3. Since standard homeowners insurance doesn't cover flooding, ensure coverage by contacting your insurance company or agent to purchase flood insurance. This must be done before there is even a threat of flooding as insurance companies stop issuing policies if there is a threat of flooding. (i.e. an approaching hurricane). Many flood insurance policies take at least 30 days to go into effect so even if you can buy it as a storm is approaching, it may not protect your investment.

–Prepare your Family/Pets

You may be evacuated, so pack in advance. Don't wait until the last moment to gather the essentials for yourself, your family and/or your pets.

–Charge Your Essential Electronics

Make sure your cell phone and portable radios are all charged in case you lose power or need to evacuate. Also make sure you have back-up batteries on hand.

–Leave

If it is likely your home will flood, don't wait to be ordered to leave; evacuate yourself! Make alternative plans for a place to stay. If you have pets, take them with you or make arrangements to board them at a facility well away from the flooding danger.

Thinkhazard:

https://thinkhazard.org/en/report/114-iceland/CF#:~:text=In%20the%20area%20you%20have,in%20the%20next%2010%20years.

Floodlist:

https://floodlist.com/europe/iceland-south-east-floods-september-2017

NOAA:

https://www.weather.gov/safety/flood-before

Science Direct: 

https://www.sciencedirect.com/science/article/abs/pii/S001282521930176X

The Smithsonian Institution National Museum of Natural History Global Volcanism Program:

https://volcano.si.edu/

Icelandic Meteorological Office (IMO):

https://en.vedur.is/