NH
Natural Hazards

Alpine environment

Alpine rock instability events and mountain permafrost

Alpine rock instability events and mountain permafrost
Rockfalls, rock slides and rock avalanches in high mountains

The terms rockfall, rock avalanche and rockslide are often used interchangeably. Different authors have proposed definitions based on volume thresholds, but the establishment of fixed boundaries can be tricky. Rockfall can be defined as the detachment of a mass of rock from a steep rock-wall, along discontinuities and/or through rock bridge breakage, and its free or bounding downslope movement under the influence of gravity[1,2]. Usually, we use this term when the volume is limited, and there is little dynamic interaction between rock fragments, which interact mainly with the substrate. Rockslides involve a larger volume (up to 100,000 m3) and the blocks often break in smaller fragments as they travel down the slope. In both rockfall and rockslide, the blocks move downslope mainly by falling, bouncing and rolling. On the other hand, rock avalanches involve the disintegration of rock fragments to form a downslope rapidly flowing, granular mass demonstrating exceptionally high mobility[3]. The size of these rock failures can vary from single boulders to several million cubic meters (e.g. the catastrophic failures of Triolet, 1717, and Randa, 1991).

[Read More]

Permafrost fever, do we need a doctor?

Permafrost fever, do we need a doctor?

Today we will shed some light on permafrost thanks to Dr. Dmitry (Dima) StreletskiyDima is an Assistant Professor of Geography and International Affairs at the George Washington University. He leads several research grants focusing on various aspects of climate change and its impacts on natural and human systems in the Arctic. Streletskiy is the President Elect of the United Sates Permafrost Association and the Chair of Global Terrestrial Network for Permafrost.

If you want to see some videos on the topic, feel free to check the following links:

Video on youtube from Siberia field class on permafrost and urban sustainability: https://youtu.be/ZlblSd4g4gE

Video on youtube from Alaska field work https://www.youtube.com/watch?v=LqYcOiCQOGk

Dima has also agreed on sharing some pictures collected during his research. So, if you are curious, just scroll to the bottom of the interview and enjoy the view!

 

Hello Dima, could you please briefly define what permafrost is for our audience?

Permafrost plays an important role in global climate change, functioning of arctic ecosystems, and human activities in the cold regions. Permafrost is soil, rock, and any other subsurface earth material that exists at or below 0°C throughout at least two consecutive years, usually for decades up to millennia. Permafrost stands for perennially frozen ground (“existing more than two years”), not permanently frozen.  I think that this is one of the major popular misconceptions about permafrost. Permafrost is not permanent and is a rather dynamic phenomenon, which makes it increasingly relevant in the context of natural hazards. Even more dynamic, is the active layer, the layer overlying the permafrost, which thaws during the summer and refreezes the following winter affecting many biological and hydrological processes in permafrost regions.

[Read More]