Week 8: Mass Wasting aka Landslides and Avalanches

This week we're discussing Mass Wasting. Mass Wasting is any downslope movement of earth material. In its more restricted sense, mass wasting refers to any rapid downslope movement of rock or soil. (Keller 210). Most of us know mass wasting by it's common name of landslide or when there is snow involved, avalanche. They range from a single boulder in a rock fall or a large mass of material in a debris flow. They can be triggered by natural events like earthquakes, volcanic eruptions and flooding, but gravity is the driving force. They can also be triggered by human activity such as mining and construction of road or buildings.

Iceland has both landslides and avalanches due to the geological landscape of the country. With it's abundance of volcanoes and glaciers along with winters that produce huge volumes of snow it's only natural that these would be a recurring hazard for the people of Iceland. I couldn't find much detailed information about landslides with regards to Iceland. There are sites that state they do occur frequently but I couldn't find any actual statistics and much of the information is in Icelandic so I was unable to read it. For the most part I found that avalanches, because of the amount of snow they get each winter, are a much bigger concern for Iceland.

Landslides in Iceland:
One recent landslide in Iceland though made the news. In 2014 a landslide in the Askja caldera occurred. Volcanoes are prone to landslides because they are constructed of loose piles of volcanic debris and lava flows on relatively steep slopes.  In this particular landslide the debris flow was so massive that it actually triggered tsunami like waves in the lake of the caldera. Some reports from early information suggest it might be 50-60 million cubic meters of material that moved and the tsunami inside the caldera is estimated to have been 73 meters high. Luckily this caldera is located in a remote part of Iceland and so there were no communities affected by this tsunami. It was though, one of the largest known landslides since the settlement of Iceland.

Askja before

Askja after landslide

Avalanches in Iceland
Avalanches are similar to landslides except that they involve the flow of snow rather than rocks and soil although they have the capability to include ice, rocks, trees, and other material if the avalanche is powerful enough. Avalanches are most common during winter or spring but glacier movements may cause ice and snow avalanches at any time of year. In mountainous terrain, avalanches are among the most serious natural hazard to life and property, with their destructive capability resulting from their potential to carry enormous masses of snow at high speeds (Wikipedia). Snow avalanches and landslides have caused both death and injury and done great damage to infrastructure and property in Iceland. In 1995 two separate avalanches, one in Flateyri and one in Sudavik caused 34 deaths between the two catastrophic events and as a consequence, Iceland's pre-existing snow avalanche and landslide regulations were completely revised. Previously these two villages had been thought safe from an avalanche hazard and so after the avalanches they had to revise their methods of research for avalanche hazard assessment. The Icelandic Meteorological Office is responsible for avalanche warnings and hazard zoning and advices the government on avalanche protective measures. The office employs snow observers in the the most important villages in avalanche-prone areas and maintains a database for avalanches. 

You can get up to date information and danger level of different areas of Iceland from this page: http://en.vedur.is/avalanches/forecast/

They even have this cool avalanche map viewer: http://en.ofanflodakortasja.vedur.is/ofanflod/

One interesting item I came across in my avalanche research had to do with the village of Flateyri. After the devastating avalanche of 1995 they built a special A-shaped earthen dam in 1998 that was built up the mountain to deflect future avalanches. It was put to the test shortly after it was completed and it worked! 

 
In February of 1999, only one year after the dams were completed, a large avalanche from Skollahvilft came crashing down into the eastern side of the dam and the avalanche went into the sea. The next winter, in March, another huge avalanche from the mountain called Innra-Bæjargil slammed into the western and the village was protected again.


Photo credit:
1.Askja landslide: http://en.vedur.is/avalanches/articles/nr/2929 
2.Flateyri protection dam: http://www.amusingplanet.com/2016/01/the-avalanche-protection-wall-of.html
3. Snow covered Flateyri: http://i.imgur.com/U6crt1E.jpg
 

Works cited:

Keller, Edward and Duane DeVecchio. Natural Hazards. New Jersey: Prentice, 2012. Print.

https://en.wikipedia.org/wiki/Avalanche

Thanks for reading!

Jennifer