EGU Blogs


Thaw Slumps of the NWT

I recently across an article that reminded me of my field work days in the early stages of my PhD in the Canadian Arctic at retrogressive thaw slumps. The article discusses the impending catastrophic drainage of a lake when the thin strip of land separating it from a thaw slump fails (see article), which it will inevitably do very soon. The story has now been picked up all across Canada in the context of climate change and permafrost melting. It was nice to see thaw slumps and permafrost in the news so I thought I’d post a few of my own pictures of these slumps from a few years ago that are very nearby the one in the article. Actually, we worked on these same slumps with Dr. Steve Kokelj from the NWT geological survey who is quoted.

Here are few of my own slump pictures from my fieldwork days in the NWT.


An aerial view of the Charras slump, which is approximately 1 km across and 30m deep at the headwall. (Photo: Matt Herod – 2011)


An aerial view of one of the smaller slumps. (Photo: Matt Herod – 2011)


My colleague, Bernard, from the uOttawa geography department headed towards the headwall for an ice sample. (Photo: Matt Herod – 2011)


A rainy day in the slump. The mudflow becomes really active when the weather is wet. (Photo: Matt Herod – 2011)


Geology Photo of the Week #44

For a bit of a change of pace the photo of the week this week isn’t a photo at all. Rather it’s a fascinating model output showing ocean surface currents in the North Atlantic. The Gulf Stream is clearly visible as it flows past Atlantic Canada and out towards the middle of the north Atlantic. I am guessing that colour scheme has something to do with current velocity or mass flux or something. Anyway, I think that red means a bigger current than blue.

Modelling is something that I have written briefly about before and am starting to get involved with in my own work. It’s a fascinating field although I believe that all model results should be taken with a grain of salt given that they try to mimic and quantify what is actually happening in nature but cannot always incorporate all of the inter-relationships that exist between the variables. This makes them only representations of what is actually occurring in the real world. However, the insane level of complexity in real systems makes models the only way to try and understand processes that we can’t observe easily. As we learn more the model can then be adjusted to incorporate new linkages and their importance more accurately.

Enough of my ranting, enjoy this unique and beautiful model output of the north Atlantic’s currents.


Surface currents in the North Atlantic– by Erik Behrens, GEOMAR, Kiel, Germany Snapshot of surface speed in a eddying (0.05°, VIKING20) ocean sea-ice model resolving important mesocale eddies and filaments explicitly.

Geology Photo of the Week #43

This weeks photo can be described by one word: mesmerizing.

Honestly, it’s hard to tell which part of this photo is better, the beautiful starry sky backdrop or the glow of Kilauea’s smoking crater. Combined, it’s just fantastic.

Kilauea is part of the Hawaiian Island volcanic chain which has been formed as the Pacific plate has moved across at hotspot. The volcano is about 300,000 to 600,000 years old.

Lava glow and space at the Kilauea volcano by Andreas Johnsson “Photo that unites the dynamic Earth and its place in Space. The photo was taken during the NASA-Nordic Winter School in Astrobiology in Hawai’i.”

Geology Photo of the Week #42

This week’s photo is a beautiful example of geochemistry in action. Briefly, travertine, which is composed of CaCO3 is often precipitated at hot springs as they emerge from the ground forming these gorgeous terraces. The reason for their formation is Henry’s gas law in action which states “the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid” which in this case is the open air. At depth, the superheated water contains lots of dissolved carbon dioxide, which lowers the water pH and allows it to dissolve carbonate minerals it comes in contact with. However, once the water reaches the surface the CO2 degasses because of the much lower partial pressure (concentration) of CO2 in the atmosphere à la Henry’s law. This causes the pH to rise which in turn leads to precipitation of dissolved carbonates such as aragonite and calcite (travertine).

By the way, I have always, always wanted to swim/lounge in one of these sorts of places but have never had the chance. Maybe one day!

Mammoth Hot Springs – travertine terrace – Credit: Joern Behrens (distributed via